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Final Conference
Fodele Beach
Crete, Greece
30 May – 3 June 2016
SOMATAI Conference, Fodele Beach Hotel, Fodele, Crete 30 May - 3 June 2016latest update: 11 May 2016
Monday, 30 May Tuesday, 31 May Wednesday, 1 June Thursday, 2 June Friday, 3 June
7:30 8:45 Breakfast8:45 9:00 Welcome by Peter Lang
9:00 9:209:20 9:409:40 10:00 Giuseppe Soligno (01.2) Teun Vissers (05.2) Andrey Milchev (08.2) Darshana Joshi (10.2)
10:00 10:20 Michael Duits (01.3) Julia Nase (05.3) Nino Chatsisvili (08.3) Mark Vis (10.3)
10:20 11:00 Coffee break Coffee break Coffee break11:00 11:20 Louis Keal (02.1) Majid Farzin (09.1) Moshe Gottlieb (11.1)
11:20 11:40 Julien Dupré de Baubigny 02.2 Yi Liu (09.2) Ciro Semprebon (11.2)
11:40 12:00 Victoria Blair (02.3) Alexander Schlaich (09.3) Sandra Boettcher (11.3)
12:00 12:20 William Trewby (02.4) Antonio Giuliani (09.4) Gerald Fuller (11.4)
12:20 13:00 Closing 12:20 - 12:3013:00 14:0014:00 15:0015:00 15:2015:20 15:4015:40 16:00 Christian Fernandez Solis (03.2) Laure Bluteau (06.2)
16:00 16:20 Ran Tivony (03.3) Antonio Aloi (06.3)
16:20 17:00 Coffee break Coffee break17:00 17:20 Frédéric Mondiot (04.1) Sahin Buyukdagli (07.1)
17:20 17:40 Maria Merola (04.2) Dino Osmanovic (07.2)
17:40 18:00 Merel van den Berg (04.3) Piotr Warszynski (07.3)
18:00 18:20 Jacinto Rosas Lugo (04.4) Soumaya Ben Jabrallah (07.4)
18:20 19:0019:00 19:3019:30 20:0020:00 21:0021:00 21:30
Time
Lunch break
Dinner18:30 - 21:30
Hotel check-infrom 14:00
Registration16:00 - 19:30
Welcome Reception18:00 - 19:30
Dinner19:30 - 21:30
Regine von Klitzing (01.1)
Roland Netz (03.1)
Hotel check-outuntil 12:00
Departure to Conference Dinner
19:30
Dinner18:30 - 21:30
Breakfast
Carlos Marques (05.1)
Poster Session
Breakfast
Veronique Schmitt (10.1)Peter Fischer (08.1)
Dominique Langevin (06.1)
Lunch breakLunch break
Excursion:Heraklion City
andKnossos Palace
Breakfast
SOMATAI Conference 2016
30 May ‐ 3 June 2016
Fodele Beach Hotel, Crete
Tuesday, 31 May 2016
Speaker Title of the Talk
8:45 9:00Peter Lang
FZ Jülich, GermanyWelcome
Session 1: Particles at fluid interfaces
9:00 9:40 01.1
Regine von Klitzing
Technische Universität Berlin
Germany
Foams and emulsions stabilized by nanoparticles of varying
hydrophobicity and shape
9:40 10:00 01.2
Giuseppe Soligno
Utrecht University
The Netherlands
Capillary‐induced self‐assembly of particles adsorbed at
fluid‐fluid interfaces
10:00 10:20 01.3
Michael Duits
University of Twente
The Netherlands
Interactions between soft microgel particles at fluid interfaces
10:20 11:00 Coffee break
Session 2: Adsorption and assembly
11:00 11:20 02.1
Louis Keal
ESPCI Paris
France
Adsorption dynamics of colloidal particles to water‐water interfaces
11:20 11:40 02.2
Julien Dupré de Baubigny
ESPCI Paris
France
Interfacial polymers H‐bond complexation: time – pH
superposition and one‐step generation of soft microcapsules
11:40 12:00 02.3
Victoria Blair
ETH Zürich
Switzerland
Towards Marangoni‐Driven Colloidal Assembly at Interfaces
12:00 12:20 02.4
William Trewby
Durham University
United Kingdom
Organisation and Dynamics of Metal Ions at Biological Interfaces
12:20 15:00 Lunch
Session 3: Charged and reactive surfaces
15:00 15:40 03.1
Roland Netz
Freie Universität Berlin
Germany
Interactions between Polar and Charged Surfaces in Water
15:40 16:00 03.2
Christian Fernandez Solis
MPIE Düsseldorf
Germany
Waterborne biopolymer‐epoxysilane hybrid films as
pretreatment for protection of reactive surfaces
16:00 16:20 03.3
Ran Tivony
Weizmann Institute of Science,
Rehovot, Israel
Direct observation of confinement‐induced charge inversion at a metal
surface
16:20 17:00 Coffee break
Session 4: Air‐water interfaces
17:00 17:20 04.1
Frédéric Mondiot
LS Instruments, Fribourg
Switzerland
Diffusing Wave Spectroscopy: Applications beyond microrheology
17:20 17:40 04.2
Maria Consiglia Merola
IESL/FORTH Heraklion
Greece
Exploring the role of molecular weight, architecture, block composition
and length on the properties of PEO‐PDMS block copolymers at the air‐
interface
17:40 18:00 04.3
Merel van den Berg
ETH Zürich
Switzerland
Non‐linear dilatational rheology of anisotropic particles at
air‐water interfaces
18:00 18:20 04.4
Jacinto Rosas Lugo
German University in Cairo
Egypt
Measuring colloidal diffusion at the water‐air interface by using
dynamic light scattering
Dinner 18:30 ‐ 21:30
Time
Foams and emulsions stabilized by Nanoparticles of varying hydrophobicity and shape
Adrian Carl, Dmitrij Stehl and Regine von Klitzing
Institut für Chemie, Angewandte Physikalische Chemie Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
Particle stabilized foams and emulsions are interesting types of dispersion with applications in various fields of technology from mineral processing and catalysis to food industry. Nevertheless, the detailed stabilization mechanisms of (nano)particles are not fully understood, yet. It has been shown that combining nanoparticles and suitable surfactants can lead to increased colloidal stability compared to the surfactant-only system without nanoparticles. As a model system, we use hydrophilic silica nanoparticles that do not attach to the water/air interface until they are modified with alkylamines which render them hydrophobic, so they become surface active [1,2]. The particle hydrophobicity was adjusted by varying the amount of adsorbed amine and/or the carbon chain length. The systems are characterized at various length scales from the nanometer to the centimeter scale. Results from surface pressure isotherms suggest the formation of a colloidal network around the air bubbles, whereby the network density correlates strongly with the foamability [1]. We determine the contact angle of the nanoparticles at the air water interface via x-ray reflectivity. Diffusing wave spectroscopy was used to probe the particles inside the foam as well as the system’s temporal evolution [3].
Fig. 1 Foam stabilization by nanoparticles – a multi-scale problem
The presented emulsions are stabilized either with fumed Silica particles or Halloysites, i.e. clay nanotubes. Although they have the same surface chemistry, their usage results in different stability behavior. Obviously, the shape has a decisive effect on the stability [4]. Their impact for catalysis is shown. [1] A. Carl, A. Bannuscher, R. v. Klitzing Langmuir (2015) 31 1615. [2] L.R. Arriaga, W. Drenckhan, A. Salonen, J.A. Rodrigues, R. Íñiguez-Palomares, E. Rio, D. Langevin Soft Matter (2012) 8 11085–97. [3] A. Carl, J. Witte, R. v. Klitzing, J. Phys. D: Appl. Phys. (2015) 48 434003. [4] D. Stehl, R. von Klitzing, Y. Lvov, H. Möhwald et al. Advanced Materials Interfaces, submitted.
Authors:
Giuseppe Soligno1, Marjolein Dijkstra2, Rene’ van Roij1
1Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena,
Utrecht University, Leuvenlaan 4, Utrecht 3584 CE, The Netherlands 2Soft Condensed Matter, Debye Institute for Nanomaterials Science,
Utrecht University, Princetonplein 5, Utrecht 3584 CC, The Netherlands
Title:
“Capillary-induced self-assembly of particles adsorbed at fluid-fluid interfaces”
Abstract:
“Particles adsorbed at a fluid-fluid interface induce deformations in the shape of the interface. These so-
called capillary deformations generate strong and long-range interactions between the particles, driving
them to assemble into 2D structures. Therefore they are of crucial relevance in the formation of 2D (or
quasi-2D) new materials.
Through a recently introduced numerical method [1], we numerically calculate the equilibrium shape of
the fluid-fluid interface for a given position and orientation of the adsorbed particles, and from this we
obtain the capillary potential between the particles. In this talk we will present results for the capillary
interactions and self-assembly of particles with various shapes and contact angles adsorbed at flat or
possibly curved fluid-fluid interfaces. In particular, we will present results for adsorbed cubes, showing
that, when they have a contact angle close to , they generate a hexapole deformation field in the
interface height profile, which drives them to assemble into hexagonal and honeycomb structures [2], as
observed experimentally [3].”
[1] G. Soligno, M. Dijkstra and R. van Roij, The Journal of Chemical Physics 141, 244702 (2014);
[2] G. Soligno, M. Dijkstra and R. van Roij, submitted;
[3] H. Evers et al., Nano Letters 13, 2317 (2013).
Interactions between soft microgel particles at fluid interfaces
Omkar Deshmukh1, Armando Maestro1,3, Dirk van den Ende1, Martien Cohen Stuart1,2 , Frieder Mugele1 , Michael Duits1
1 Science and Technology, University of Twente, Netherlands; 2 Agrotechnology and Food Science, Wageningen University and Research Centre, Netherlands; 3 Biological and Soft Systems, University of Cambridge, United Kingdom
We studied the adsorption and interactions of poly(NIPAM) particles (Volumetric Phase Transition at 32oC) at
Air-Water and Oil-Water interfaces. Experiments with a Langmuir Trough in combination with characterization
of the molar mass, allowed measuring the hitherto unknown equation of state. From it, we found that adsorbed
particles are strongly stretched, giving rise to discernable surface pressures even at low coverage densities.
Combining these results with measurements of how the surface pressure of a Pendant Bubble evolves in a
freshly created pNIPAM solution, allowed to analyze the adsorption kinetics. Diffusive transport and the
creation of a (growing) adsorption barrier as the adsorption proceeded, were corroborated. Remarkably, the
final area per particle was practically the same for all bulk pNIPAM concentrations; suggesting a drastic change
in the adsorption barrier and/or net adsorption energy as the coverage density reaches this value. Additional
experiments at the Oil/Water interface using Pendant Drops afforded well-defined variations of both
temperature and droplet area. Cycling between 24oC and 36oC indicated a full reversibility of the surface
pressure, while large stepwise reductions in the droplet area resulted in surface pressure responses without a
relaxation time. These findings suggest that the pNIPAM particles adsorb irreversibly. Remarkably, raising the
temperature from 24oC to 36oC gave a significant increase in surface pressure, in spite of the considerable
shrinkage of the particle in the bulk liquid. This trend will be tentatively explained.
Response of the interfacial tension of a poly(NIPAM) coated aqueous drop in oil, to changes in temperature. Green circles: drop created at 36oC and cycled between 36 and 24 degrees C. Blue circles: drop created at 24oC. Grey areas denote the part of the temperature cycle at 36oC while blank spaces correspond to 24oC. The inset shows a schematic of the proposed particle conformations in the aqueous phase at the two temperatures.
References:
1. Hard and soft colloids at fluid interfaces: Adsorption, interactions, assembly & rheology; O.S. Deshmukh, D. van den Ende, M. Cohen Stuart, F. Mugele and M.H.G. Duits, Adv. Coll. Interf. Sci, (2014)
2. Equation of state and adsorption dynamics of soft microgel particles at an air-water interface; O.S. Deshmukh, A. Maestro, M.H.G. Duits, D. van den Ende, M. Cohen Stuart and F. Mugele, Soft Matter 10 (2014)
Adsorption dynamics of colloidal particles to water/water interfaces
Louis Keal, Hans Tromp, Cécile Monteux ‘Water/water emulsions’ are phase-separated solutions of incompatible aqueous polymers, with physical properties very different to oil/water emulsions, most notably a very low surface tension and broad, osmotically compressible interface. Applications include food texturing, where they may function as fat-free emulsions. Colloidal particles and proteins go to the interface and can stabilize the droplets of W/W emulsions, eg. protein-stabilised PEO/Dextran solutions[1]. However, the driving force leading to the adsorption of such particles and the stabilization mechanism of such systems is still unclear. We study the adsorption dynamics of individual colloidal particles at the interface between a fish gelatin solution and a dextran solution, both food-grade biopolymers. We observe a spontaneous breach of the particles at the interface sudden breach followed by slow relaxation, considerably slower than predicted by balancing capillary vs. viscous forces. Moreover, the unique properties of the water / water interface make the explanation of the activated hopping of a contact line over nanoscale surface heterogeneities unlikely. We find that the slow dynamics and emulsion instability are both likely related to the adsorption of gelatin to the particle surface. [1] Balakrishnan et. al, dx.doi.org/10.1021/la204825f | Langmuir 2012, 28, 5921 −5926
Abstract for SOMATAI conference
Interfacial polymers H-bond complexation: time – pH
superposition and one-step generation of soft microcapsules
Julien Dupré de Baubigny1*, Caroline Fradin1, Nadège Pantoustier1, Patrick Perrin1, Mathilde
Reyssat1, Cécile Monteux1.
1 École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research
University, Sciences et Ingénierie de la Matière Molle (SIMM), CNRS UMR 7615, 10 rue Vauquelin, F-75231 Paris
cedex 05, France
* This author will present the paper.
Synthetic capsules fabrication is growing fast through its highly diversified applications: from
food industries to local drug delivery, from personal care products to oil recovery
enhancement.
To protect the inner fluid droplets from coalescence and to build a strong membrane layer-by-
layer processes need two polymers which bind to each other, most of the time two opposite
polymers electrolytes are used, but hydrogen bonds are also
employed1. The method is robust and versatile by changing the
number of layers, although it is a multistep, non-continuous,
product-consuming and very time-consuming process. Some
recent progresses have been made with microfluidic devices,
but only low volumes can be used. Direct interfacial
complexation is an alternative powerful technic which consists
in bringing through each liquid phase two interacting polymers
directly at their interface (Figure 1). The main advantage is
that it can be done in one step process. Recent studies have
reported the production of capsules obtained by interfacial
coacervation of oppositely charged polyelectrolytes2. The main
challenge that remains to be addressed is the control of
strength, the permeability and the biocompatibility of the
membrane.
We use hydrogen bonds to obtain pH sensitive capsules obtained by direct interfacial
complexation using a proton donor in the aqueous phase (polyacrylic acid) and a proton
acceptor in the oil phase (polypropylene oxide); the obtained capsules are made with
biocompatible materials. These capsules can be produced by two complementary techniques:
emulsification (Figure 2) by applying a strong shear or by flow-focusing set up in a microfluidic
device. By raising the pH both types of capsules can be dissolved to deliver the oil.
By measuring the interfacial rheological properties of this membrane using a Double-Wall-Ring
apparatus we find a clear pH-dependence of viscoelastic properties of the membrane. In fact,
we show that the rheological properties can be rescaled on a time-pH master curve. The
rheological behaviour can be varied from purely viscous to purely elastic by simply varying the
pH. We show that there is a critical pH above which the interfacial complex dissociates
corresponding to a critical degree of negative charges on the proton donor.
Figure 1 - Scheme of direct interfacial complexation on an oil drop (yellow) in water. Red: oil soluble polymer. Purple: water
soluble polymer.
Figure 2 – Vial photography and microscope observation of emulsions. Left: capsules made by emulsification at
low pH are stable to time and soft strain. Right: capsules made at higher pH vanishes instantly. Scale bar:
100µm.
1. Le Tirilly, S. et al. Interplay of Hydrogen Bonding and Hydrophobic Interactions to Control
the Mechanical Properties of Polymer Multilayers at the Oil–Water Interface. ACS Macro
Lett. 4, 25–29 (2015).
2. Kaufman, G. et al. Single-step microfluidic fabrication of soft monodisperse polyelectrolyte
microcapsules by interfacial complexation. Lab. Chip 14, 3494–3497 (2014).
3. Spruijt, E., Sprakel, J., Lemmers, M., Stuart, M. A. C. & van der Gucht, J. Relaxation
Dynamics at Different Time Scales in Electrostatic Complexes: Time-Salt Superposition.
Phys. Rev. Lett. 105, 208301 (2010).
Towards Marangoni-‐Driven Colloidal Assembly at Interfaces Blair, V.; Vermant, J. Fabrication of thin films is an extremely valuable tool in the creation of surfaces with designed functional properties, derived from controlled roughness, periodicity or structure. Examples of applications include anti-‐reflect coatings, planar waveguides or transparent conducting films. The classical Langmuir-‐Blodgett method of deposition of molecular or colloidal species at fluid interfaces offers a lower cost and environmentally gentler procedure compared to gas-‐phase methods often employed industrially, however, by being driven by a physical barrier compression the process is difficult, if not impossible to scale up. This work investigates the use of Marangoni flows, generated by small temperature gradients across the interface, combined with rheological insights, to transport interfacial material at constant surface pressure, thereby working towards the development of a scalable, continuous deposition process at liquid interfaces.
30-Jan-16
Organisation and Dynamics of Metal Ions at Biological Interfaces
William Trewby ([email protected]), Kislon Voïtchovsky
Durham University, The Palatine Centre,
Stockton Road, DH1 3LE,
United Kingdom
The specific interaction between metal ions and cells membranes has long been known to affect membrane stiffness, permeability and the adsorption behaviour of macromolecules such as proteins. Ionic effects can drive spontaneous membrane curvature and heterogeneous charge distributions at the interface with the surrounding medium. However, the complex cocktail of channel proteins, cholesterol and phospholipids making up cell walls in vivo limit the ability of simulations or large-scale models to probe these localised effects.
Atomic force microscopy (AFM) can resolve individual ions at model biological interfaces and map the hydration layers adjacent to membranes. This allows for examination of molecular-level effects such as specific ionic interactions that cannot be understood in the framework of continuum models. Advances in the technique now allow the tracking of single ions’ adsorption/desorption dynamics with a time resolution of ~25 ms.
Here, amplitude-modulation AFM is used to investigate the spatial organisation of monovalent ions at an anionic, gel-phase lipid bilayer. The nature of the condensed layer of ions at the surface is shown to vary dramatically depending on the size of the cation. This can be explained by the competition between the metal and hydronium (H30+) ions as they neutralise the negatively-charged surface. Small-amplitude force spectroscopy also elucidated the position of the ionic layer above the membrane. The results have important implications for signal transduction, phospho-lipid synthesis and pH sensing in cells.
Fig. 1: Gel-phase supported lipid bilayers imaged with AM-AFM in aqueous buffer. Each image demonstrates the effects of different monovalent ions: (a) NaCl, (b) KCl, (c) RbCl. The scale bar is 3 nm and the colour scale runs
from 0 pm (black) to 200 pm (white) in each case
Interactions between Polar and Charged Surfaces in Water
Roland R. Netz, Alexander Schlaich, Matej Kanduc
Department of Physics, Free University of Berlin, 14195 Berlin, Germany
The molecular layer of water molecules on surfaces, the so-called hydration layer, is crucial for the properties of biological and technological surfaces. We study the interaction between two hydrated surfaces using a novel simulation technique that allows to efficiently determine the interaction pressure at prescribed water chemical potential. Prior research concentrated on the two limiting scenarios, namely hydrophobic attraction (or cavitation) between hydrophobic surfaces, and hydration repulsion for very polar (i.e. very hydrophilic) surfaces [1]. Recent experiments demonstrated weak attraction between mildly hydrophilic surfaces, i.e. surfaces for which the contact angle is slightly smaller than 90 degrees. Using atomistic simulations, we show that hydrophilic attraction occurs quite generally for surfaces that favorably interact with water and among themselves. For the important case of two dissimilar surfaces we constitute the universal adhesion diagram in terms of the surface contact angles, distinguishing dry adhesion, hydration repulsion and cavitation-induced attraction regimes [3]. For charged surfaces interactions are calculated and compared with Poisson-Boltzmann theory, deviations can be rationalized in terms of the dielectric constant in thin aqueous slabs.
Figure 1: Dry adhesion and hydration repulsion state for two polar surfaces
References: [1] Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization, E. Schneck, F. Sedlmeier, R. R. Netz, PNAS 109, 14405 (2012) [2] Attraction between hydrated hydrophilic surfaces, M. Kanduc, E. Schneck, R. R. Netz, Chemical Physics Letters Frontiers Article, 610-611, 375-380 (2014) [3] From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces, R.R: Netz, M. Kanduc, PNAS 112, 12338 (2015)
Direct observation of confinement-induced charge inversion at a metal surface
Ran Tivony, Dan Ben Yaakov, Gilad Silbert* and Jacob Klein
Dept. of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
*Current address: Adama Makhteshim Ltd., Beer Sheva, 84100, Israel
Surface interactions across water are central to areas from nanomedicine to colloidal stability.
They are predominantly a combination of attractive but short-ranged dispersive (van der Waals)
forces, and long-ranged electrostatic forces between the charged surfaces. Using a surface force
balance, we showed that electrostatic forces between two surfaces across water, one at constant
charge (a dielectric) while the other (a molecularly-smooth metal surface) is at constant potential
of the same sign, may revert smoothly from repulsion to attraction on progressive confinement of
the aqueous intersurface gap. This remarkable effect, long predicted theoretically in the classic
Gouy-Chapman (Poisson-Boltzmann) model but never previously experimentally observed,
unambiguously demonstrates surface charge reversal at the metal-water surface.
Its experimental demonstration emphasizes the importance of taking such charge reversal – and
the accompanying cross-over from repulsion to attraction – into account, for interactions
between dielectrics and metal surfaces in aqueous media in similar circumstances. These include
phenomena such as colloidal interactions, adsorption of proteins, cells or nanoparticles on metal
surfaces, imaging of metal surfaces by ceramic AFM tips and tribology of dielectric-metal
interfaces in aqueous surroundings.
Tivony, R.; Ben-Yaakov, D.; Silbert, G.; Klein, J., Direct observation of confinement-induced charge
inversion at a metal surface, Langmuir 2015.
Diffusing Wave Spectroscopy: Applications beyond microrheology
Frédéric Mondiot and Andreas C. Völker1
1LS Instruments, Fribourg, Switzerland
E-mail: [email protected]
Diffusing Wave Spectroscopy (DWS) is a modern light scattering technique that allows the quantitative measurement of microscopic motion in soft mater systems. DWS naturally applies to highly turbid media such as concentrated suspensions, emulsions, foams, or gels. In these opaque mixtures, light is scattered multiple times by the dispersed solid, liquid, or gaseous particles, and its intensity fluctuates over time as a consequence of Brownian motion. Acquisition and analysis of the intensity fluctuations of the scattered light by means of the intensity correlation function enables to determine, within the diffusion approximation, the mean square displacement (MSD) of the dispersed particles. Upon application of the generalized Stokes-Einstein relation to the particle MSD, the frequency-dependent storage G’(ω) and loss G’’(ω) moduli of the medium can be subsequently determined. So far microrheology has been the main application of DWS. Today it is a well-established technique to study the rheological properties of colloidal materials at high frequency range, and has been specifically useful to precisely determine the gel point. Recently, however, it was possible to extend the application of DWS beyond microrheology. We present two new applications of DWS. Firstly, we demonstrate that DWS is able to measure the size of particles or droplets in optically dense dispersions with an accuracy larger than previously assumed (±5%). We show how DWS sizing is successfully applied to the monitoring of Ostwald ripening taking place in a concentrated oil-in-water emulsion. Secondly, we show for the first time that DWS can monitor both the phase transitions occurring during the drying of colloidal coatings like paint films, i.e. from the liquid state to the crystalline state through a glass state, and the development of a skin at the air/film interface, which, to the best of our knowledge, no other experimental technique can do at the moment.
Title: Exploring the role of molecular weight, architecture, block composition and length on
the properties of PEO-PDMS block copolymers at the air-interface.
Authors: Maria Consiglia Merola1 (speaker), Maria Sevastaki1, Moshe Gottlieb2, Dimitris Vlassopoulos1
1 FORTH, Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece
2Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
Abstract:
During the last decades, the interfacial activity of amphiphilic block copolymers has been widely studied.
The great interest comes from the peculiar characteristics of these systems: they combine the amphiphilic
nature of small molar-mass surfactants with the conformational and compositional richness of
macromolecules. Hence, their behavior at fluid interfaces can lead to tunable properties with significant
implications in many scientific and industrial fields where multiphasic systems are used. For example,
viscoelastic properties at the interface can play a relevant role in the processing of emulsion and foams.
Generally, block copolymers exhibit a wide range of rheological properties and interfacial activity,
depending on several parameters.
The amphiphilic block copolymers examined in the present work are composed of Poly(ehtylene oxide)
(PEO) as the hydrophilic block and Poly(dimethylsiloxane) (PDMS) as the hydrophobic block. Our aim was
to understand the relation between the molecules conformational characteristics, such as molecular weight,
block lengths, molecular architecture and PEO/PDMS ratio, with the corresponding interfacial behavior and
rheological properties at the interface. To this end, we used a series of well-characterized block copolymers
and followed a protocol consisting on drop-wise deposition of a given sample (from dilute solution) on a
Langmuir trough and performing repeated compression-expansion cycles and linear viscoelastic
measurements by means of the magnetic rod interfacial stress rheometer. Our results are discussed
phenomenologically in terms of the role of block length and composition as well as in terms of existing
theories for mushroom-to-brush transition in grafted chains. In particular, we show how one can affect the
apparent surface pressure isotherms at the molecular scale and the consequences on the film’s reversibility
and rheology.
Measuring colloidal diffusion at the water-air interface by using dynamic light
scattering Jacinto Rosas1,2; Reinhard Sigel1
1 Physics department. The German University in Cairo. Main entrance El-Tagamoa El-Khames. New Cairo city, Egypt
2Presenting author
Diffusion of colloids is a phenomenon with potential applications in rheological characterization of monolayers at fluid-fluid interfaces [1]. The high aspect ratio of colloids as interfacial probes could enable characterization for monolayers of small shear viscosity still keeping large the Boussinesq number, which sets a limit for the interfacial sensitivity of experimental measurements. The development of suitable experimental methodologies for determining the diffusion dynamics of the colloid at the interface is among the key steps for increasing the practicality of the technique. So far, particle tracking microscopy is the technique being used for measuring diffusion of colloids at interfaces. Moreover, Stocco et al., 2011 [2] applied dynamic light scattering for measuring the diffusion of colloids at a water-oil interface. Here we report the application of dynamic light scattering for determining the diffusion coefficient of polymer colloids at the surface of water -or water-air interface-. The dependence of the colloidal diffusion with the concentration of the colloids at the interface and the temperature of the system have been evaluated. The quality and reproducibility of the experimental data confirm the suitability of the technique for measuring interfacial diffusion of colloids. Some factors introducing errors in the measurements are also evaluated. Although particle tracking microscopy have been efficient so far in determining diffusion dynamics of colloids at interfaces, dynamic light scattering offers some complementary advantages such as enabling data analysis without tracking algorithms, a higher interfacial sensitivity, or employing particle probes with smaller size.
References 1. Joseph R. Samaniuk and Jan Vermant. Micro and macrorheology at fluid–fluid
interfaces. Soft Matter, 10(36):7023–7033, may 2014. 2. Antonio Stocco, Tahereh Mokhtari, Günter Haseloff, Andreas Erbe, and
Reinhard Sigel. Evanescent-wave dynamic light scattering at an oil-water interface: Diffusion of interface-adsorbed colloids. Physical Review E, 83(1), jan 2011.
SOMATAI Conference 2016
30 May ‐ 3 June 2016
Fodele Beach Hotel, Crete
Wednesday, 1 June 2016
Speaker Title of the Talk
Session 5: Membranes and biofilms
9:00 9:40 05.1
Carlos Marques
ICS‐CNRS‐Université de Strasbourg
France
Sliding Tethered Ligands: lock and key colloidal interactions with a
topological twist
9:40 10:00 05.2
Teun Vissers
University of Edinbourgh
United Kingdom
High‐throughput characterisation of bacterial surface adhesion and
post‐adhesion dynamics
10:00 10:20 05.3
Julia Nase
Technische Universität Dortmund
Germany
Solid‐supported lipid membranes at high hydrostatic pressure ‐ an X‐
ray reflectivity study at the solid‐liquid interface
10:20 10:40
10:40 11:00
11:00 12:00
12:00 13:00
13:00 15:00 Lunch
Session 6: Emulsions and foams
15:00 15:40 06.1
Dominique Langevin
Université Paris Sud
France
Properties of surfactant monolayers and their relation to
microemulsions, emulsions and foams properties
15:40 16:00 06.2
Laure Bluteau
ESPCI Paris
France
Stability of a water film between a solid surface and an oil droplet
16:00 16:20 06.3
Antonio Aloi
TU/e Eindhoven
The Netherlands
iPAINT: interface Point Accumulation for Imaging in Nanoscale
Topography
16:20 17:00 Coffee break
Session 7: Electrostatic interactions at interfaces
17:00 17:20 07.1
Sahin Buyukdagli
Bilkent University Ankara
Turkey
Charge correlations and solvent structure in confined electrolytes
17:20 17:40 07.2
Dino Osmanovic
Bar‐Ilan University, Ramat‐Gan
Israel
Effect of non‐specific interactions on formation and stability of specific
complexes
17:40 18:00 07.3
Piotr Warszynski
Polish Academy of Sciences
Krakow, Poland
Permeability of alginate containing multilayer films cross‐linked by
multivalent cations
18:00 18:20 07.4
Soumaya Ben Jabrallah
CEA Saclay
France
Ion Distribution at Interfaces By X‐Ray Standing Wave Technique
19:30 Departure Conference Dinner
Poster Session
Time
Sliding Tethered Ligands: lock and key colloidal interactions with a
topological twist
Carlos M. Marques, Martin Bauer, Christophe Fajolles, Thierry Charita,
Jean Iss, Patrick Kékicheff, Jean Daillant
Institut Charles Sadron, CNRS, University of Strasbourg, France.
Specific adhesion is mediated by specific lock and key interactions
between ligand-receptor pairs. The complementary moieties are
anchored to the substrates by ubiquitous tethers that control the
interaction range and the mobility of the ligands and receptors, allowing
for an efficient tuning of the kinetics
and strength of the binding events
between colloidal or biological
interfaces. In this work, we add
topological interactions to the toolbox
of ligand-receptor design by
developing a family of tethered
ligands for which the spacer can slide
at the anchoring point. Our results
show that this additional sliding
degree of freedom changes deeply
the nature of the adhesive contact, in
particular by extending the spatial range over which the binding forces
may sustain a significant value. The introduction of sliding tethered
ligands with self-adjustable length paves the way for the development of
versatile specific adhesion substrates that can better accommodate
surface roughness and dynamic fluctuations.
Sliding tethered ligands add topological interactions to the toolbox of ligand–receptor
design; Bauer, M.; Kékicheff, P.; Iss, J.; Fajolles, C.; Charitat, T.; Daillant, J.;
Marques, C.M.; Nature. Communications. 2015, 6, 8117.
Membrane insertion of sliding anchored polymers; Bauer, M.; Bernhardt, M.; Charitat,
T.; Kékicheff, P.; Fajolles,C.; Fragneto, G.; Marques, C.M.; Daillant, J. Soft Matter
2013, 9,1700.
High-throughput characterisation of bacterial surfaceadhesion and post-adhesion dynamics
T. Vissers, N. Koumakis, V. A. Martinez, M. Hermes, J. Schwarz-Linek,A. T. Brown, A. B. Schofield, A. Dawson, J. Arlt, and W. C. K. Poon
SUPA and School of Physics & Astronomy, The University of Edinburgh, James ClerkMaxwell Building, Peter Guthrie Tait Road, Edinburgh EH9 3FD, Scotland, UK
E-mail: [email protected]
The physics governing the adhesion of bacteria on surfaces is important for understanding
biofilm formation [1,2]. This ubiquitous form of surface colonisation begins with a small num-
ber of bacteria adhering to a fluid-solid interface [3]. The importance of variations in adhesion
properties between different cells within a population is poorly understood. Here, we study the
dynamics and adhesion of a clonal population of Escherichia coli (E. coli) on treated glass sur-
faces. High-throughput procedures and algorithms are used to track the dynamics of individual
bacteria and distinguish between cells that are either freely swimming, diffusing, or adhering
to the surface. We show several new approaches to quantitatively characterise bacterial adhe-
sion, and reveal differences between individual cells both in their capacity to adhere, as well as
their post-adhesion dynamics. We explain how post-adhesion dynamics can be used to study
bacteria-surface interactions and compare results for several genetically modified E. coli strains
and in-house synthesized bacteria-shaped colloids.
Swimming Di using Adhering
2D Tracks viewed from below= depth of eld
Adhering bacteria
di using and swimming bacteria
Left: sketch of bacteria on a surface, the inset shows three trajectories viewed from below.
Right: measured adhering fraction of E. coli for various concentrations of added surfactant [4].
References[1] J. Costerton, P. S. Stewart, and E. Greenberg, Science, 284, 1318 (1999).
[2] L. Hall-Stoodley, J. W. Costerton, and P. Stoodley, Nature Reviews Microbiology, 2, 95(2004).
[3] H. H. Tuson and D. B. Weibel, Soft Matter, 9, 4368 (2013).
[4] J. Schwarz-Linek, J. Arlt, A. Jepson, A. Dawson, T. Vissers, D. Miroli, T. Pilizota,V. A. Martinez, W. C. K. Poon, Colloids and Surfaces B: Biointerfaces, 137, 2 (2016).
Solid-supported lipid membranes at high hydrostatic pressure - an X-ray reflectivity study at the solid-liquid interface
Benedikt Nowak1, Michael Paulus1, Julia Nase1, Paul Salmen1, Florian J. Wirkert1, Patrick Degen2, Metin Tolan1
1Fakultät Physik / DELTA, Technische Universität Dortmund, 44221 Dortmund, Germany
2Fakultät Chemie, Physikalische Chemie II, Technische Universität Dortmund, 44221 Dortmund, Germany
In living organisms, cell membranes regulate the mass transfer between the intracellular and extracellular regions. The basic membrane structure consists of a lipid bilayer where cholesterol and proteins are included. These systems undergo pressure- and temperature-induced phase transitions. While extreme conditions in general are unfavorable for animate beings, some organisms are able to withstand surprisingly harsh conditions. The high flexibility in lipid membranes, based on the high lateral mobility that is provided by the liquid phase and the existence of so-called lipid rafts, is essential to fulfill specific functionalities. Although the structural properties of membranes are altered by extreme conditions, some species are adapted to live at low temperatures and high pressures, e.g. in the Mariana trench. Thus, it is interesting to understand the effect of pressure on the characteristics of lipid membranes in depth.
While pressure-dependent phase transitions were studied in bulk solutions in detail in the literature, the behaviour of water-immersed solid-supported membranes under pressure is widely unknown. As a simple model system for highly complex biological membranes, we prepared lipid multilayers composed of phospholipids (DMPC) on hydrophilic silicon surfaces by spin-coating. The structure of these multilayers at the solid-liquid interface between the substrate and an aqueous buffer was studied in situ by x-ray reflectometry at pressures of up to 4500 bar.
In dependence on the pressure, the DMPC multilayers showed several phase transitions from the liquid into different gel phases. The phase behavior was similar to that of bulk systems, but the bilayer spacing was decreased because of the bounding to the substrate. A detailed analysis of the electron density profiles showed that the region between the head groups was successively filled with water molecules with rising pressure, starting from the top-most layers. This effect was inverted by a pressure release, yielding a lower hydration compared to the initial system. Finally, it was shown that pressure increase can trigger the formation of lipid multilayers in situ. This effect is completely reversible when HHP is applied. In that way, we obtain a way to switch the state of a lipid layer from bi- to multilayer and back in situ, without changing the sample.
Properties of surfactant monolayers and their relation to microemulsions, emulsions and foams properties
Dominique Langevin
Université de Paris Sud, France
Surfactants form monolayers at the air‐water and oil‐water interface, which can be characterized by a
number of properties : surface tension, static and dynamic, surface curvature elasticity, surface
compression and surface shear elasticities and viscosities. We will show how the knowledge of these
properties allows predicting the behavior of oil/water or air/water dispersions. For instance, for
microemulsions that are thermodynamically stable dispersions, one can predict dispersion type and size,
as well as interfacial tensions between microemulsions, oil and water. For emulsions and foams that are
thermodynamically unstable dispersions, the prediction of dispersion type and size is more difficult and
will be discussed. Surfactant layer properties also control the destabilization processes : gravity effects
(creaming, sedimentation, drainage), Ostwald ripening and coalescence of drops or bubbles (although in
this case experimental evidence is still scarce
Stability of a water film between a solid surface and an oil droplet
by Laure Bluteau a,b
, François Lequeux a, Laurence Talini
a, Emilie Verneuil
a, Maurice Bourrel
b, Nicolas Passade-
Boupat b
Laboratoire commun Physico-Chimie des Interfaces Complexes a Science et Ingénieries de la Matière Molle, CNRS UMR 7615, ESPCI ParisTech, PSL Research University, 10, rue
Vauquelin 75005 Paris b Pôle Etudes et Recherche de Lacq, Total S.A., BP 47, 64170, Lacq
If water-in-oil or oil-in-water emulsions have been studied for decades, the drainage and the stability of a water film between an oil droplet and a solid have received less attention1, although they are key parameters for the efficiency of oil recovery.
To experiment the drainage of a water film between a solid and an oil droplet, we have chosen to approach an oil droplet surrounded by water toward a glass substrate. As it moves, the droplet is deformed and water is trapped between the droplet and the solid. This water film is initially thicker at its center, this shape is called dimple (see Figure). Once the dimple formed, the droplet is immobilized. Then the water film drains, until equilibrium is reached. This drainage is observed thanks to a three wavelength interferometry technique (see Image), allowing us to map out the absolute thickness of the film. The experimental profiles of the film, at equilibrium and during drainage, will be compared to theoretical
predictions; our aim is to study the impact of short range interactions onto the stability and the drainage of the film.
Experiments with a droplet of dodecane in aqueous solutions of salt (NaCl) at varied concentrations have shown that the film stability at equilibrium depends on salt concentration. At low concentration, the films are stable and their thickness depends on the Laplace pressure of the droplet. Here, repulsive electrostatic interactions are at stake.
As for the drainage dynamics, at early times, the film is thick enough so that the interactions between the oil/water and water/solid interfaces can be neglected. As a consequence, the drainage can be entirely described by the hydrodynamic pressure field. We derive the governing non-dimensional equation of this hydrodynamic drainage2. Thanks to a combination of simple scaling arguments and numerical calculations we obtain the time evolution of the dimple. When the film has thinned enough to be under a critical thickness (depending on the nature of the short range interactions), the drainage is no longer purely hydrodynamic but also controlled by the interactions between the interfaces. We evidenced this second regime that we were able to model theoretically and observe experimentally. Altogether, we quantitatively probe the influence of the short range interactions on drainage and equilibrium state.
[1] C.S. Tan, M.L. Gee, G.W. Stevens, Langmuir, 2003, 19, 7911-7918 [2] S. Hartland, J.D. Robinson, Journal of Colloids and Interface Sci., vol 60, n°1, 1977
iPAINT: interface Point Accumulation for Imaging in Nanoscale Topography Authors: Aloi Antonio*1, 2, Vilanova Neus1, 2, Albertazzi Lorenzo3, Voets Ilja1, 2, 4. 1 Institute for Complex Molecular Systems, Eindhoven University of Technology, Post Office Box 513, 5600 MD Eindhoven, Netherlands. 2 Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Post Office Box 513, 5600 MD Eindhoven, Netherlands. 3 Nanoscopy for nanomedicine group, Institute for Bioengineering of Catalonia (IBEC), C. Baldiri Reixac 15‐21, 08028 Barcelona, Spain. 4 Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Post Office Box 513, 5600 MD Eindhoven, Netherlands. * Presenting author. Interfaces are ubiquitous and key determinant of the interactions between the building blocks of most soft materials. While super‐resolution microscopy is widely used to visualize objects tagged with fluorescent probes with nanometric resolution, imaging interfaces which cannot be labeled with resolution below the diffraction limit remains a challenge. Ambitious cases are ice crystals (solid/liquid), air nanobubbles (air/liquid) and emulsions (liquid/liquid). Thus, we set out to develop a new super‐resolution approach tailored to study interfaces, which we coin ‘iPAINT’: interface Point Accumulation for Imaging in Nanoscale Topography. iPAINT is a combination of PALM and PAINT microscopy, based on aspecific physical adsorption onto interfaces of polymer chains tagged with a PALM dye which are present at micromolar concentrations in the bulk solution. This ensures a constant flux of probes and a continuous replacement of photobleached dyes due to molecular exchange of probes between the solution and the interface. Three‐dimensional iPAINT imaging on colloidal dispersions, air nanobubbles and water/octanol nanoemulsions, validates the method as a powerful tool for non‐invasive, high‐resolution imaging of complex soft materials. Finally iPAINT paves the way for investigating the topology of ice crystals, notoriously unlabelled structures, so far mostly explored at the macroscale. This gives the possibility to achieve a nanometer mapping of the crystals surfaces and to study the influence at the molecular level of specific ice‐binding proteins on phenomena such as ice‐recrystallization inhibition, thermal hysteresis and ice shaping.
Charge correlations and solvent structure in confined electrolytes
Sahin Buyukdagli1
1 Department of Physics, Bilkent University, Ankara 06800, Turkey
Water mediated electrostatic interactions between ions and polymers are omnipresent in various nanoscale sys-tems. From water nanofiltration and polymer translocation to energy storage in supercapacitors, these interactionsare at the heart of many biological and industrial processes. However, for several decades, the theoretical un-derstanding of electrostatic interactions has been limited to mean-field dielectric continuum models such as thePoisson-Boltzmann formalism, which bypass the charge structure of the water solvent and electrostatic correlationeffects. The talk will focus on newly developed theoretical approaches that aims at overcoming these limitations.
The first part of the talk will be devoted to beyond-mean-field dielectric continuum theories such as the electro-static one-loop and self-consistent approaches. By comparisons with Monte-Carlo simulations of inhomogeneouselectrolytes, I will characterize ionic fluctuation effects on the partition of charged liquids at dielectric membranes[1] and the ionic selectivity of membrane nanopores [2]. Next, I will couple this formalism with the Stokes equa-tion and introduce a correlation-corrected ion and polymer transport theory [3]. By comparison with ion transportexperiments [4], I will first show that the low ionic conductivity of open α-Hemolysin pores can be quantitativelyexplained by the presence of surface polarization effects. In DNA-blocked nanopores, the addition of multivalentcounterions into the solution will be shown to stop the electrophoretic translocation of the DNA molecule and toreverse its motion. This mechanism that was recently measured in translocation experiments [5] can be used effi-ciently to improve the accuracy of translocation-based sequencing methods by maximizing the duration of DNAtranslocation events. In the case of hydrodynamically induced DNA translocation, the same correlation effects willbe shown to reverse the sign of the ionic current through the nanopore, while the DNA velocity remains intact [6].
In the second part of the talk, I will present a solvent-explicit electrolyte model that overcomes the dielectric con-tinuum approximation [7,8]. Within this theory, the consideration of the solvent charge structure allows to explainthe non-local dielectric response of polar solvents observed in Molecular Dynamics simulations [9]. Then, the in-teraction of solvent molecules with the membrane surface results in an interfacial solvent depletion and dielectricscreening deficiency. It will be shown that this effect can solely explain the experimentally observed low capac-itance of carbon-based materials, improving the prediction of the mean-field dielectric continuum electrostaticsby an order of magnitude. I will conclude by presenting a brief summary of open questions in the theoreticalmodelling of inhomogeneous charged liquids.
[1] S. Buyukdagli, C.V. Achim, and T. Ala-Nissila, J. Chem. Phys. 137, 104902 (2012).[2] S. Buyukdagli and T. Ala-Nissila, J. Chem. Phys. 140, 064701 (2014).[3] S. Buyukdagli and T. Ala-Nissila, Langmuir 30, 12907 (2014).[4] D.J.Bonthuis, J. Zhang, B. Hornblower, J. Mathe, B.I. Shklovskii, and A. Meller, Phys. Rev. Lett. 97, 128104(2006).[5] S. Qiu, Y. Wang, B. Cao, Z. Guo, Y. Chen, and G. Yang, Soft Matter 11, 4999 (2015).[6] S. Buyukdagli, R. Blossey, and T. Ala-Nissila, Phys. Rev. Lett. 114, 088303 (2015).[7] S. Buyukdagli and T. Ala-Nissila, Phys. Rev. E 87, 063201 (2013).[8] S. Buyukdagli and R. Blossey, J. Chem. Phys. 140, 234903 (2014).[9] D.J. Bonthuis, and R.R. Netz, Langmuir 28, 16049 (2012).
Effect of non-specific interactions on formation and stability of specific complexes
Dino Osmanovic; Yitzhak Rabin
Bar-Ilan University, Ramat-Gan, Israel
We introduce a simple model to describe the interplay between specific and non-specific
interactions, and study how these are affected by the phase of the system. We study the influence of
various physical factors on the static and dynamic properties of the specific interactions of our
model and show that contrary to intuitive expectations, non-specific interactions can assist in the
formation of specific complexes and increase their stability. We then discuss the relevance of these
results for biological systems.
Permeability of alginate containing multilayer films cross-linked by
multivalent cations
K. Kilan1, L. Szyk-Warszynska1, G.J.M. Koper2, P. Warszynski1*
1J.Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Krakow, Poland
2Department of Chemical Engineering of the Delft University of Technology, Delft, The Netherlands
Multiayer ultrathin films can find application as functional coatings or separation, semipermeable membranes in biomedical area, hence, they should be biocompatible and they should have well characterized permeation behaviour towards some specified molecules (drugs, ions). We prepared the multilayer films were via the layer-by-layer (LbL) method using sodium alginate (ALG) and poly-L-arginine (PLArg) as the polyelectrolyte pair. Alginate is a natural polysaccharide derived from brown algae that unique feature is the ability to crosslink into hydrogel in presence of some cations. Therefore during films build-up they were contacted with salt solutions with non-crosslinking NaCl, MgCl2 and crosslinking cations CaCl2, BaCl2, AlCl3 and GdCl3 solutions. The QCM-D, ellipsometry and FTIR-ATR were applied to characterize the multilayer films build-up. The cyclic voltammetry rotating disc electrode technique was applied to characterize the permeation of films for charged probe molecules (potassium ferrocyanide/ferricyanide redox pair). We found that the crosslinking of films induces 3-fold increase of their mass/thickness. High water content is partly responsible for that increase as they contain 60-80% of water. That increase of thickness is not accompanied by decrease of films permeability. We found the irrespective of crosslinking the dependence of permeablilty on the number of deposited polyelectrolyte was similar (see. Fig.1.). The transfer of charged probe within film was systematically reduced with the increasing number of layers and the transition between permeation modes was observed when the film reached a threshold number of layers, largely independent on the salt solution (crosslinking or not), despite large differences in the film thickness. We used a simple model of the hollow membrane to describe the experimental findings. We also tested the biocompatibility of the membranes by MTT test and cell morphology on the HEK 293 and THP-1 cell lines. The films appeared to be non-toxic even though potentially toxic cations Ba2+, Gd3+ were used for the alginate crosslinking.
Fig.1. Electrochemical permeability, defined as ratio of cathodic limiting currents on electrode covered with multilayers to one on bare electrode, as the function of number of layers of PLArg/ALG films rinsed with salts as indicated in the graph.
Ion Distribution at Interfaces By X-Ray Standing Wave Technique
Soumaya ben Jabrallah, Florent Malloggi, Luc Belloni, Jean Daillant
Electrolytes and charged interfaces are of utmost practical importance for surface driven transport phenomena such electrophoresis which are sensitive to charge distribution. Measuring such charge distributions is experimentally challenging since it requires to measure ion distributions with an exquisite resolution and sensitivity. Indeed, the ionic concentration deviates from the bulk concentration only in the diffuse layer depending on the solution concentration. Recently, we developed a method based on x-ray standing waves and microfabrication which allows the determination of ion distributions with a sub-nm resolution. The aim of the experiment was to measure the ionic distributions on solid/liquid interface for different ions and different surfaces.
SOMATAI Conference 2016
30 May ‐ 3 June 2016
Fodele Beach Hotel, Crete
Thursday, 2 June 2016
Speaker Title of the Talk
Session 8: Liquid‐liquid Interfaces
9:00 9:40 08.1
Peter Fischer
ETH Zürich
Switzerland
Rheological and structural properties of interfacial adsorption layers
under human gastric conditions
9:40 10:00 08.2
Andrey Milchev
Bulgarian Academy of Sciences
Sofia, Bulgaria
Effect of Composition, Stiffness and Size of Nonionic Surfactants on the
Surface Tension at Oil‐Water Interfaces ‐ a Molecular Dynamics
Investigation
10:00 10:20 08.3
Nino Chatsisvili
NIZO Food Research, Ede
The Netherlands
Food‐grade colloidal particles at liquid‐liquid interfaces
10:20 11:00 Coffee break
Session 9: Near‐interface dynamics and friction
11:00 11:20 09.1
Majid Farzin
IPF Dresden
Germany
Steady state shear motion of a polyelectrolyte brush bi‐layer
with oppositely charged polyelectrolyte stars in an ionic liquid: A
molecular dynamics simulation study with DPD thermostat
11:20 11:40 09.2
Yi Liu
Forschungszentrum Jülich
Germany
Near‐wall dynamics of a novel aqueous colloidal model system: an
EWDLS study
11:40 12:00 09.3
Alexander Schlaich
Freie Universität Berlin
Germany
Transition from Wet to Dry Friction
12:00 12:20 09.4
Antonio Giuliani
IESL/FORTH Heraklion
Greece
Near‐wall Velocimetry by Evanescent Wave Dynamic Light
Scattering on a Rheometer
12:20 15:00 Lunch
15:00 15:30
15:30 16:00
16:00 16:30
16:30 17:00
17:00 17:30
17:30 18:00
18:00 18:30
Dinner 18:30 ‐ 21:30
Time
Excursion to
Heraklion and
Knossos Palace
Rheological and structural properties of interfacial adsorption layers under human gastric conditions
P. Fischer1, N. Scheuble1, T. Geue2, F. Carrière3
1 Institute of Food, Nutrition and Health, ETH Zürich, 8092 Zürich, Switzerland 2 Laboratory of Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland 3 CNRS & Aix-Marseille Université, Enzymologie Interfaciale et Physiologie de la Lipolyse, 31 chemin
Joseph Aiguier, 13402 Marseille cedex 20, France
Human lipid digestion begins at the interface of oil and water by interfacial adsorption of lipases. Tailoring the surface area for lipase activity can lead to specific lipid sensing in the body, hence defined satiety hormone release [1]. The properties of the surface area is linked with the stability of the lipid emulsion [2], and as emulsion stability is directly influenced by the interfacial structure, we tailor the composition of interfacial active material to generate interfacial membranes, which vary in their gastric stability. Besides controlling nutritional uptake, the mechanical performance of materials at oil/water interfaces after consumption is also a key factor affecting hydrophobic drug release. The viscoelasticity of interfacial adsorption layers formed by biopolymers was monitored online by interfacial rheology applying several in vitro digestion steps. These observations allowed understanding and thus manipulating their viscoelastic layer evolution during in vitro digestion. Whereas a protein based membrane (b-lactoglobulin) softened and finally degraded during proteolysis, its combination with methylcellulose thermogelled and was stable during enzymatic degradation (gastric lipolysis and proteolysis). Thus, by adjusting the degree of hydrophobicity of methylcellulose the interfacial elasticity and thermogelation of the adsorption layer can be varied. Coexistence of both emulsifiers at the interface is shown by neutron reflectometry measurements, where morphological information is extracted as depicted in the following images [3, 4].
Left: Interfacial rheology of the composite -llactoglobulin/metNCC layer as a function of environmental conditions. Right: Scattering length density (sld) as a function of layer depth with layer illustration of the fitted parameters.
Emulsions formed by these emulsifiers showed that gastric lipolysis of oil depend not only on the interfacial composition, but also on the thickness of the interfacial biopolymer layer: At a critical concentration of methylcellulose gastric lipolysis was completely inhibited. The utilized layers and their analysis provide knowledge of physicochemical changes during in vitro digestion of interfaces, which promote functional food formulations. The substantial structural and mechanical change of methylcellulose interfaces at body temperature represents also a controllable encapsulation parameter allowing optimization of lipid-based drug formulations.
[1] Marciani L. et al.: British Journal of Nutrition 101 (2009) 919-928 [2] Golding M. et al.: Current Opinion in Colloid and Interface Science 15 (2010) 90-101 [3] Scheuble N. et al.: Biomacromolecules 15 (2014) 3139-3145 [4] Scheuble N. et al.: Langmuir 32 (2016) 1396-1404
Effect of Composition, Stiffness and Size of Nonionic Surfactants on theSurface Tension at Oil-Water Interfaces - a Molecular Dynamics Investigation
Andrey Milchev1, Hristina Popova1∗, and Sergei Egorov2,1Institute of Physical Chemistry,
Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria2 Department of Chemistry, University of Virginia,
Charlottesville, VA 22901, USA
Using extended Molecular Dynamics simulation, we model adsorption of linear polymers on theinterface between two immiscible liquids. By varying the size, stiffness and composition of nonionicsurfactants, we examine the impact on surface tension γ at the liquid/liquid phase boundary betweenimmiscible liquids (e.g., oil and water).
Our results indicate that alternating A − B-copolymers are much more efficient than homo- ordiblock copolymers in reducing γ whereas γ itself is hardly sensitive regarding surfactant molecularweight, except for the case of A− B-diblocks, where the shortest chains are also the most efficientones in diminishing surface tension.
Special attention is payed to the influence of surfactant rigidity on the surface tension. Increasingstiffness is found to make surfactants significantly less efficient with regard to γ reduction. In addi-tion, increased stiffness of surfactant chains leads to formation of rafts or bundles on the interface,cf. Fig. 1, which are observed to form Janus-like blocks at higher concentration when diblock copoly-mers are used. For short surfactants the tilt angle of such blocks increases steadily with increasingdegree of coverage surface. The variation of other thermodynamic and structural properties withsurfactant concentration is also studied.
0
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FIG. 1: Side view (left) and top view (right) snapshots ofdiblock AB-surfactants of length N = 10, NA = NB = 5 (thered A- and blue B-blocks), flexible (top) and rigid (bottom)with stiffness κ = 15 and coverage Θ = 2.25 at the inter-face between two immiscible liquids,“water” (cyan) and “oil”(orange).
Food‐grade colloidal particles at liquid‐liquid interfaces
Nino Chatsisvili1,2, Albert P. Philipse1 and R. Hans Tromp1,2
1 Van ’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nano‐materials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
2 NIZO food research, Kernhemseweg 2, 6718 ZB Ede, The Netherlands The aim of this project is to synthesize particles (10-1000 nm) from food-grade proteins, such as zein and gluten, using the anti-solvent precipitation method and study their activity at liquid-liquid interfaces. Colloidal particles that stabilize emulsions by adsorbing at the interface are called Pickering particles, and the respective emulsions, Pickering emulsions, as opposed to the surfactant-stabilized emulsions. Pickering emulsions have various technological applications, due to their outstanding stability against coalescence. Two types of liquid-liquid interfaces are studied here, water-water and oil-water inter-faces. The first occur between phase-separated aqueous solutions of incompatible polymers (e.g. proteins and polysaccharides) and their most characteristic property is the ultra-low interfacial tension (a few μN/m or less) compared to oil-water interfaces. Zein particles are found to accumulate and even form clusters at the water-water interface between aqueous solutions of fish gelatin and dextran. Particle clusters are able to arrest eventually the late stage of the demixing process by the formation of a well-stabilized interfacial particle-rich layer with a morphology similar to an air-in-water foam. This layer - dubbed as ’foam-like’ layer - contains droplets of one phase, surrounded by particle-stabilized lamellae of the other phase. Despite the adsorption of zein particles at water-water interfaces, no macroscopic stabilization of emulsions is observed. Similar behaviour is shown by zein particles at oil-water interfaces, where the particle accumulation and clustering are easily observed, despite again the fact that macroscopic stabilization of emulsions against creaming or sedimentation and/or lowering of the interfacial tension are not achieved. However, particles synthesized from protein gluten show a completely different behavior at oil-water interfaces compared to zein particles. Specifically, gluten particles are able to lower the interfacial tension of emulsions and form a well-stabilized water-in-oil foam. Foam morphology and stability over time is studied in terms of gluten particle concentration, pH, ionic strength and mixing conditions. Furthermore, the different behavior of zein and gluten particles at oil-water interfaces is attempted to be explained on the grounds of their hydrophobicity, size, charge and/or tendency to form aggregates.
Steady state shear motion of a polyelectrolyte brush bi-layer with oppositely charged polyelectrolyte stars in an ionic liquid: A molecular dynamics simulation study with DPD thermostat
M. Farzin, T. Kreer, J. U. Sommer
Molecular dynamics simulations are employed to study polyelectrolyte-brush bilayers with embedded polyelectrolyte stars under steady-state shear motion of two grafting surfaces. We use the Ewald-summation method to incorporate electrostatic interactions and the dissipative-particledynamics thermostat to account for hydrodynamic correlations. To study the influence of electrostatic interactions, we vary both the Bjerrum length and the fraction of charged brush monomers. Increasing the strength of electrostatic interactions leads to a slightly smaller osmotic pressure concomitant with a larger shear stress. Consequently, the resulting kinetic friction coefficient increases upon increasing of Bjerrum length or charge density. We relate this result to conformational properties, such as the distribution of stars within the bilayer, which depend strongly on the electrostatic interactions. Our study provides a significant advance towards a more realistic modeling of biological transport processes as they have previously preformed for electrically inert brushes of PEB without inclusions.
Near-wall dynamics of a novel aqueous colloidal model system: an EWDLS study
Y. Liu, P.R.Lang Institute of Complex Systems - Soft Condensed Matter (ICS-3),
Forschungszentrum Jülich Soft matter at aqueous interfaces has acquired a growing attention from scientific community and industry during recent years. The spectrum of topics includes: interface-induce self-assembly, crystalline colloidal array for optical application, corrosion protection, water-borne 'green' coating, to name a few. The dynamics of colloidal particles at interface is an important feature through this spectrum, since it plays a central role in microfluidic technology, emulsion stabilization, and many lab-in-chip applications. The motion of colloidal particles is known to be hindered at interface due to hydrodynamic interactions (HI), which might have significant implication on technology. To fully explore the effect, it is important to obtain a comprehensive understanding, both experimentally and theoretically. Evanescent dynamic light scattering has been proved to be a sensitive and reliable experimental technique for the study of near-wall dynamics of colloidal particles. In our previous effort, near-wall dynamics of colloidal hard spheres dispersed in organic solvent has been systematically studied over a broad range of volume fractions; experimental results were thoroughly compared with predictions based on virial approximation and simulation and an agreement has been reached. The agreement between experiments and prediction has provided a framework for the understanding of near-wall dynamics in general, and paved the path for the study of more complex system, such as charged particles in aqueous solution. Despite it high potential, EWDLS hasn't been employed to study the near-wall dynamics of particles in aqueous solution. The main challenge is to find a suitable aqueous model system, which is monodisperse and could be index matched to the aqueous solution. PEGylated fluorinated latex particles could be a promising model system, since it has fulfilled the requirements of being monodisperse, iso-refractive index and stable. Moreover, as the PEG-mediated interaction could be tuned by varying the PEG chain length, salt concentration and solvent composition. In this contribution, PEGylated fluorinated particles will be used as an aqueous model system, and the near-wall dynamic of this system will be discussed in depth, with variation of volume fraction and interaction ranges.
The dielectric response of aqueous water slabs in nanoconfinement
Alexander Schlaich and Roland R. Netz
Department of Physics, Free University of Berlin, 14195 Berlin, Germany
The dielectric constant of water in nanoconfinement is crucial for nanofluidics and
nanochemistry, but also for modeling the electrostatic interaction between extended surfaces
and biological membranes and for understanding electrokinetics [1].
The dielectric response at interfaces shows rich features that have profound influence on zeta
potential and capacitance [2]. Using atomistic simulations at prescribed water chemical
potential [3], we present spatially resolved dielectric profiles of water confined between
hydrophilic surfaces and show that the water orientation becomes correlated in planar
confinement, resulting in a drastic change of the local dielectric response tensor. We also
study the dielectric response in the presence of ions.
References:
[1] D. J. Bonthuis and R. R. Netz, “Unraveling the Combined Effects of Dielectric and Viscosity Profiles on
Surface Capacitance, Electro-Osmotic Mobility and Electric Surface Conductivity,” Langmuir, 2012.
[2] D. J. Bonthuis, S. Gekle, and R. R. Netz, “Dielectric Profile of Interfacial Water and its Effect on Double-Layer
Capacitance,” Phys. Rev. Lett., vol. 107, no. 16, p. 166102, Oct. 2011.
[3] A. Schlaich, B. Kowalik, M. Kanduč, E. Schneck, and R. R. Netz, “Simulation Techniques for Solvation-
Induced Surface-Interactions at Prescribed Water Chemical Potential,” in Computational Trends in Solvation and
Transport in Liquids, vol. 28, G. Sutmann, J. Grotendorst, G. Gompper, and D. Marx, Eds. Jülich:
Forschungszentrum Jülich GmbH, 2015, pp. 155–185.
Figure 1: Interaction between charged hydrophilic surfaces with counterions.
Near-wall Velocimetry by Evanescent Wave Dynamic Light Scattering on a Rheometer
Antonio Giuliani, Ruel McKenzie, Benoit Loppinet
IESL-FORTH, Heraklion, Greece.
Classical assumptions like no-slip boundary conditions and continuity in stress and
flow profiles are all but universal in flow. Specially when one considers
multicomponent fluids like colloidal suspension and polymer solutions; the
interplay of mechanical properties of the fluid, hydrodynamic and chemico-physical
interactions with the wall result in discontinuities and non-adhesion of the fluid to
the walls. Those issues are not fully resolved; advancement of relevant
experimental techniques is therefore needed. We present an implementation of
evanescent wave dynamic light scattering for near-wall velocimetry (100 nm from
surface range) on a rotational rheometer. With this technique, we gain access to
the near-wall velocity as well as to the near-wall flow profile. This tool is of
relatively easy implementation on commercial rheometers making it a useful tool
for understanding and tuning the near-wall flow and therefore in validating
rheological measurements. Here we present the principles of the technique and
demonstrate the technique on a simple Newtonian fluid, a colloidal suspension and
a polymer solution on non-treated silica surfaces. We find ideal linear flow for the
Newtonian fluid; while on the other samples we record different near-wall
velocities, therefrom, we deduce non-zero slip lengths.
SOMATAI Conference 2016
30 May ‐ 3 June 2016
Fodele Beach Hotel, Crete
Friday, 3 June 2016
Speaker Title of the Talk
Session 10: Pickering emulsions
9:00 9:40 10.1
Véronique Schmitt
CRPP University of Bordeaux
France
Brief Review about Pickering Emulsions
9:40 10:00 10.2
Darshana Joshi
University of Cambridge
United Kingdom
Heterogeneous Pattern Formation of Small Colloids Grafted to Large
Oil Droplets Using DNA
10:00 10:20 10.3
Marc Vis
Eindhoven University
The Netherlands
Physical Chemistry of Water‐in‐Water Pickering Emulsions
10:20 11:00 Coffee break
Session 11: Wetting, spreading and contact angles
11:00 11:20 11.1
Moshe Gottlieb
Ben Gurion University, Beer Sheva
Israel
The “interface rush” – kinetics of amphiphilic polymers towards and
onto newly formed liquid‐liquid interfaces
11:20 11:40 11.2
Ciro Semprebon
University of Edinburgh
United Kingdom
Liquid Infused Substrates: statics and dynamics
11:40 12:00 11.3
Sandra Boettcher
Technische Universität Berlin
Germany
Quillaja saponin: An emulsifier unlike common low‐molecular
weight surfactants
12:00 12:20 11.4
Gerald Fuller
Stanford University
USA
Spreading of Miscible Liquids
12:20 12:30 Closing
Hotel check‐out until 12:00
Time
Brief Review about Pickering Emulsions
Véronique Schmitt
Centre de Recherche Paul Pascal, Univ. Bordeaux, CNRS UPR 8641, 33600 Pessac, France
Emsulsions are usually stabilized by surfactant or small adsorbing polymers. Although
early described by Ramsden and Pickering [1,2], emulsions stabilized by colloidal particles
have fallen into oblivion for a long period of time before regaining interest at the end of the
1990s beginning of the 2000s.
Such kind of emulsions are very diverse due to a large variety of possible particles
going from naturally occurring to synthesized either through organic or inorganic chemistry,
from hard to very deformable ones and from spherical to non spherical ones. Despite this
huge diversity, I will highlight the common features and original properties of particle-
stabilized emulsions like elaboration of monodisperse emulsions through limited coalescence
process (Fig. 1), interfacial plasticity... I will propose some remaining open questions that I
think, are worth further investigations [3]. Finally I will show some materials deriving from
such emulsions.
Figure 1. Example of a Pickering emulsion easily obtained with turbulent stirring
[1] W. Ramsden, Proc. Royal Soc. 72 (1903) 156
[2] S.U. Pickering, CXCVI. – Emulsions, J. Chem. Soc., Trans. 91 (1907) 2001.
[3] V. Schmitt et al. C. R. Physique 15 (2014) 761–774
Heterogeneous Pattern Formation of Small Colloids Grafted to Large Oil Droplets Using DNA Authors Darshana Joshi1, Dylan Bargtail2, Alessio Caciagli1, Jerome Burelbach1, Zhonyang Xing1, Jasna Bruijc2, Nuno Machado Araujo3, Erika Eiser1* 1 University of Cambridge, Department of Physics - Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK 2 Center for Soft Matter Research & Department of Physics, New York University, New York, 10003, USA 3University of Lisbon, Portugal.
Abstract Fluid-fluid interfaces are omnipresent in biological, everyday life, and industrial processes. Understanding the dynamics, aggregation and pattern formation of solid particles at these interfaces is important for enabling the design of novel approaches and materials for future applications. We introduce a novel approach to stabilize fluid interfaces with hard colloidal spheres using selective binding via DNA [1, 2]. Different to Pickering emulsions our approach enables the controlled and reversible assembly of particles at the interface [3]. For this we functionalize surfactant stabilized larger oil-droplets with single-stranded (ss) DNA and mix them with small colloids grafted with the complementary ssDNA. We make two important observations: Firstly, because of the mobility of the DNA attached to the oil-water interface the resulting binding density of the colloids becomes dependent on the colloidal concentration in bulk. Secondly, once colloidal adsorption is saturated a rich phase diagram of colloidal aggregation emerges, which is controlled by the excess concentration of the added surfactant micelles inducing depletion [4]. Varying the micelle concentration in the aqueous phase, a purely entropic transition from a fluid-like phase to a more compact packing of the solid colloids at the interface is observed. This is supported by simulation studies. The richness of length scales and interactions present in this system can also be extended as a model system for understanding the role played by depletion forces and substrate stiffness in cellular organization. Finally, the DNA binding provides a thermally controlled, reversible way to release the colloids from the interface [5].
References [1] L D Michele and E Eiser, Phys. Chem. Chem. Phys., 2013,15, 3115-3129(2013) [2] F Varrato, L D Michele, M Belushkin, N Dorsaz, S H Nathan, E Eiser, G Foffi, PNAS, 109, 47,19155–19160, (2012) [3] Vignati E, Piazza R, Lockhart TP (2003) Pickering emulsions: Interfacial tension, colloidal layer morphology, and trapped-particle motion. Langmuir 19(17):6650–6656 [4] L D Michele, T Yanagishima, A R. Brewer, J Kotar, E Eiser, and S Fraden, Phys. Rev. Lett. 107, 136101 (2011) [5] Marenduzzo D, Finan K, Cook PR (2006) The depletion attraction: An underappreciated force driving cellular organization. J Cell Biol 175(5):681–686.
Physical Chemistry of Water-in-Water Pickering Emulsions M. Vis1*§, R.H. Tromp1,2, B.H. Erné1
1 Van ’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science,
Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
2 NIZO food research, Kernhemseweg 2, 6718 ZB Ede, The Netherlands
Solutions of two different polymers in water commonly phase separate above a certain total
polymer concentration [1], typically 10% by mass, and the two resulting coexisting phases are each
enriched in one of the polymers. The water–water interface has many peculiar properties [2], such
as an electric potential step [3], an ultralow interfacial tension [4,5], and a width of the order of ten
nanometer [6], complicating the preparation of stable water-in-water emulsions.
We found that ultrathin colloidal platelets are effective stabilizers of water-in-water emulsions [7].
Because the rim of plate-like particles accommodates (nearly) any contact angle, they surprisingly
feature stronger adsorption than spheres of equal surface area. Moreover, the nanoplatelets have
a low buoyant mass that preserves slow sedimentation of the nearly density matched emulsion.
Our conclusions are underpinned with detailed experiments on the physical chemistry of our novel
water-in-water emulsions.
References
[1] M. Vis, V. F. D. Peters, B. H. Erné, and R. H. Tromp, Macromolecules 48, 2819 (2015).
[2] M. Vis, B. H. Erné, and R. H. Tromp, Biointerphases 11, 018904 (2016).
[3] M. Vis, V. F. D. Peters, R. H. Tromp, and B. H. Erné, Langmuir 30, 5755 (2014).
[4] M. Vis, V. F. D. Peters, E. M. Blokhuis, H. N. W. Lekkerkerker, B. H. Erné, and R. H. Tromp,
Phys. Rev. Lett. 115, 078303 (2015).
[5] M. Vis, V. F. D. Peters, E. M. Blokhuis, H. N. W. Lekkerkerker, B. H. Erné, and R. H. Tromp,
Macromolecules 48, 7335 (2015).
[6] R. H. Tromp, M. Vis, B. H. Erné, and E. M. Blokhuis, J. Phys.: Condens. Matter 26, 464101
(2014).
[7] M. Vis, J. Opdam, I. S. J. van 't Oor, G. Soligno, R. van Roij, R. H. Tromp, and B. H. Erné,
ACS Macro Lett. 4, 965 (2015).
§ present address: Physical Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
The “interface rush” – kinetics of amphiphilic polymers towards and onto newly formed liquid-liquid interfaces
Liat Laufer, Mor Armon, and Moshe Gottlieb
Department of Chemical Engineering, Ben-Gurion University, Beer-Sheva 84105, Israel
The stability and shape of equilibrated interfaces are determined by the static interfacial properties. For newly formed interfaces the dynamic properties are of interest, and for interfaces under stress interfacial rheology is the dominating feature. All of these interfacial properties could be manipulated by using surfactants with prescribed surface activity, dynamics, and interfacial rheology. For this to be achieved the details on how the interfacial properties are affected by the specific surfactant are required. The design of system involving newly formed interfaces in a surfactant solution emerging from a nozzle and broken up into a spray of droplets or exposed to another insoluble liquid may serve as an example in which understanding of interfacial dynamics and kinetics are required. Foam emerging from a beer tap, milk flowing through a homogenizer, inkjet droplets impacting the substrate, a shampoo undergoing rigorous agitation upon hair wash, suds in a washing machine, are all characterized by interfaces under stress while being formed, broken, and reformed, and whose performance is affected by the interfacial dynamics and rheology. Moreover, understanding of interfacial dynamics may contribute to the elucidation of biophysical processes such as protein diffusion onto membranes or bioprocesses involving vesicles. Yet, most of the systems mentioned above typically involve a mixture of several structurally complex surfactant macromolecules. The use of synthetic, well characterized polymers affords isolation of the different variables affecting the systems behavior.
In this talk we will focus on one aspect of this problem - the relation between the molecular structure of block copolymers and the kinetics of their diffusion towards and adsorption onto a newly formed liquid-liquid interface. Two types of block copolymers were studied: PEO-PDMS and PS-polypeptide. The molecular parameters to be examined include average molecular weight, blocks size ratio and diblock vs. triblock structure. The role of molecular dimensions and architecture, thermodynamic driving force and tendency towards aggregation in the bulk are reviewed.
Liquid Infused Substrates: statics and dynamics.
Ciro Semprebon1 and Halim Kusumaatmaja2
Email:[email protected] 1School of Engineering, University of Edinburgh, Edinburgh EH9 3FB, UK
2Department of Physics, Durham University, Durham DH1 3LE, UK
A novel class of functional surfaces, termed liquid infused surfaces, has recently been introduced, and they have been shown to exhibit a wide-range of advantageous surface properties. To date, however, there is no theory for predicting the contact angle and contact angle hysteresis of a liquid droplet on these surfaces, despite their relevance as key design parameters for any application involving liquid infused surfaces. In this talk I will illustrate our recent theory [1], showing that unlike standard wetting problems, the contact angle is not uniquely defined by material parameters, but also has a strong dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. I will validate the predictions for equilibrium shapes with Finite Element calculations, and address the drop dynamics employing a recently developed ternary Lattice Boltzmann model [2].
Fig: Schematic illustration of the effect of the Laplace Pressure of the oil-gas interface on the drop morphology on a liquid infused substrate.
References: [1] C. Semprebon, G. McHale and H. Kusumaatmaja: "Apparent Contact Angle and Contact Angle Hysteresis on Liquid Infused Surfaces ", Submitted. [2] C. Semprebon, T. Krüger and H. Kusumaatmaja: "Ternary free-energy lattice Boltzmann model with tunable surface tensions and contact angles", Physical Review E, 93, 3 (2016).
Quillaja saponin: An emulsifier unlike common low-molecular weight surfactants
Authors: Boettcher, S; Drusch, S
The interfacial properties of Quillaja saponins (QS) are very different from those of common low
molecular surfactants. Quillaja saponins are natural emulsifiers and can be extracted from the soap bark
tree Quillja saponaria Molina. The extract consists of several different saponin derivates which differ in
amount, position and type of sugar residues as well as the type of aglycone. Differences in saponin
composition, even between different QS extracts, affect interfacial properties tremendously. Quillaja
saponins were classified as an ionic surfactant, but the prediction of interfacial behavior remains a
challenge since Quillaja saponins have unique properties. Quillja saponins can form highly viscoelastic
interfacial films, adsorb slower than common low-molecular weight surfactants (mixed-barrier
controlled) at the interface and can efficiently lower the dynamic interfacial tension. Additionally, very
stable foams can be produced even at very low concentrations.
We characterized the interfacial and foam properties of Quillaja saponins in relation to five other
saponins. We therefore used a two-fluid needle system coupled with drop shape analysis to determine
short-term adsorption and related those to foam properties. Additionally, we characterized the
interactions of Quillaja saponins with the whey protein beta-lactoglobulin (β-LG) at the interface and
molecular level. Basic interfacial tension properties were characterized with dynamic interfacial tension,
short-term adsorption, foam and dilational shear oscillation experiments. To study molecular
interactions fluorescence quenching was analyzed and interactions at the interface were determined
with sequential two-fluid needle experiments. We showed that β-LG and Quillaja saponins can have
synergistic foam properties and fluorescence measurements showed that both interact via static
quenching (complexation). We showed that short- and midterm adsorption behavior was not linked to
foam properties. Although no clear correlation can be found between dilational and shear viscoelasticity
and foam properties we showed that foam stabilization of QS is similar to proteins. QS and β-LG both
stabilize foams because of the interaction between molecules at the interface and therefore formation
of high viscoelastic films.
Spreading of Miscible Liquids
Walls, D., Haward, S., Shen, A., Fuller, G. Miscible liquids commonly contact one another in natural and technological situations, often in the proximity of a solid substrate. In the scenario where a drop of one liquid finds itself on the solid surface and immersed within a second, miscible liquid, it will spread spontaneously across the surface. We show experimental findings of the spreading of sessile drops in miscible environments that have distinctly different shape evolution and power law dynamics from sessile drops that spread in immiscible environments, which have been reported previously. Figure 1a,b shows a sessile droplet of corn syrup resting on a hydrophilic surface and spreading into water. Note that the spreading proceeds by an elevated “skirt” of corn syrup emanating from the leading edge of the droplet. The three phase contact line, on the other hand, moves outward at a markedly slower speed. We develop a characteristic time to scale radial data of the spreading sessile drops based on a drainage flow due to gravity. This time scale is effective for a homologous subset of the liquids studied. However, it has limitations when applied to significantly chemically different, yet miscible, liquid pairings; we postulate that the surface energies between each liquid and the solid surface becomes important for this other subset of the liquids studied. Initial experiments performed with pendant drops in miscible environments support the drainage flow observed in the sessile drop systems. Figure 1c shows the evolution of a pendant drop of corn syrup spreading into water through an interfacial drainage flow that has corn syrup accumulating at the drop apex prior to forming a streaming jet.
Figure 1. (a) The side view of a sessile drop of corn syrup spreading into a ambient environment of water. The black arrow marks the location of the leading edge of an elevated “skirt” of partially dissolved cornsyrup that has drained off the drop surface. The white arrow marks the location of the three phase contact line on the hydrophyillic glass substrate. (b) The bottom view of the corn syrup sessile droplet showing the two propagating interfaces. (c) The side view of a pendant drop of corn syrup interacting with a surrounding bath of water. As time proceeds, slightly dissolved corn syrup drains downward and accumulates at the apex of the drop prior to forming a strong jet.
SOMATAI Conference 2016
30 May ‐ 3 June 2016
Fodele Beach Hotel, Crete
Wednesday, 1 June 2016
10:20 ‐ 13:00
Poster Session
Main author (alphabethical order) Title of the poster contribution
1
Christian Appel
TU Darmstadt
Germany
Ultra‐thin Polymer Films and Nanocomposites at the Air‐Water Interface
2
Melanie Arangalage
ESPCI Paris
France
Boiling and Aphroicity of oil mixtures
3
Edgar M. Blokhuis
Leiden University
The Netherlands
Density Functional Theory of a Curved Liquid‐Vapour Interface
4
Mariano Brito
Forschungszentrum Juelich
Germany
Ultrafiltration of charge‐stabilized suspensions: Theory and experiment
5
Karsten Busse
Martin‐Luther‐University Halle
Germany
Crystallization of PEO at the air‐water interface
6
Greet Dockx
KU Leuven
Belgium
Coalescence of particle‐stabilized droplets using microfluidics
7
Michael Duits
University of Twente
Netherlands
Cationic Hofmeister Series of Wettability in Mica‐Water‐Alkane Systems
8
Noa Iuster
Weizmann institute of Science
Rehovot, Israel
Hydration lubrication in polymeric thin layers
9
Nir Kampf
Weizmann Institute of Science
Rehovot, Israel
Lubrication between Hydrophobic and Hydrophilic Surfaces across Aqueous
Solutions
10
Agnieszka Ksiazkiewicz
MPI for Iron Research Düsseldorf
Germany
Electrochemical synthesis of sp2 carbon films on zinc from polysaccharide
and gelatin thin film precursors
11
Maria Consiglia Merola
IESL/FORTH Heraklion
Greece
Coalescence Inhibition through Asphaltene Adsorption
12
Ahmad Moghimikheirabadi
ETH Zurich
Switzerland
Surface Rheology of Block‐Copolymer Stabilized Interfaces
13
Laila Maria Moreno Ostertag
MPI für Eisenforschung
Germany
Interfacial forces and solvation on Nafion® membrane model systems with varying
hydrophobicity
14
Debashish Mukherji
MPI for Polymer Research
Germany
Co‐non‐solvency phenomena in bulk and adsorbed smart polymer solutions
15
Gerhard Nägele
Forschungszentrum Jülich
Germany
Effect of competing short‐range attraction and long‐range repulsion on the
dynamics of globular particle dispersions
1
SOMATAI Conference 2016
30 May ‐ 3 June 2016
Fodele Beach Hotel, Crete
Wednesday, 1 June 2016
10:20 ‐ 13:00
Poster Session
Main author (alphabethical order) Title of the poster contribution
16
Lucie Nova
Charles University in Prague
Czech Republic
Molecular Simulations of flower‐like micelles and micellar gels
17
Karolina Podgórna
Polish Academy of Sciences
Poland
Formation of polyelectrolytes shells on nanogels surfaces
18
Alexander Schlaich
Freie Universität Berlin
Germany
The dielectric response of aqueous water slabs in nanoconfinement
19
Anja Schröder
Wageningen University
The Netherlands
New food emulsions stabilised by submicron‐scale lipid particles
20
Maria Sevastaki
University of Crete, Heraklion
Greece
Acrylic polymers at fluid interfaces
21
Reinhard Sigel
German University in Cairo
Egypt
Correlation Ellipsometry
22
Marta Szczech
Polish Academy of Sciences
Krakow, Poland
Influence of the surface properties of colloidal poly(ε‐caprolactone) nanospheres on
its stability in bio‐fluids
23
Krzysztof Szczepanowicz
Polish Academy of Sciences
Krakow, Poland
Pegylated polyelectrolyte multilayer films as the “antifouling” coatings protecting
against non‐specific proteins adsorption
24
Neus Vilanova Garcia
TU/e Eindhoven
The Netherlands
Supramolecular Pickering Emulsions
25
Rachel Yerushalmi ‐ Rozen
Ben‐Gurion University
Israel
Nano‐structures mediated assembly of small molecules and polymers
26
Ruyi Zheng
DSM Urmond
The Netherlands
Polyurethane – Water Interfaces studied with Fiber Probes
2
Ultra-thin Polymer Films and Nanocomposites at the Air/Water
Interface
Christian Appel*†, Martin Kraska*†, Markus Gallei*‡, Bernd Stühn*†
† Intitut für Festkörperphysik, Technische Universität Darmstadt, D-64289 Darmstadt,
Germany
‡ Ernst-Berl-Institut für Technische und Makromolekulare Chemie, Technische Universität
Darmstadt, D-64287 Darmstadt, Germany
We investigate ultra-thin polymer films and nanocomposites at the air/water
interface. Our research is focused on their surface dynamics and rheology,
including relaxation processes, crystallisation processes and its behaviour
under mechanical stress. In detail, we prepare Langmuir monolayers on water
surfaces consisting of homo polymers (poly (ferrocenyldimethylsilane), PFS,
which is able to crystallize) or diblock copolymers (PFS – poly (2 – vinyl
pyridine), P2VP), monolayers of nanoparticles (silica) and nanocomposites of
these polymer and nanoparticle systems. We probe all these thin films by
mechanical stress using different Langmuir setups (e.g. surface rheology by
oscillating barrier setup). In order to get a thorough understanding of the
microscopic and mesoscopic structure of the thin films we perform in-situ
Brewster-Angle-Microscopy (BAM) and in-situ X-Ray reflectometry (XRR). Thin
films of PFS show surface crystallisation which is progressively hindered when
PFS is combined with increasing molecular weight of P2VP in a diblock
copolymer. We also present results on the mechanical response of these
systems in the semi-dilute regime, i.e. Maxwell-body type response. We
present first results of mechanical properties and structure of silica
nanoparticle films at the water surface including first experiments on
nanocomposites of these particles and PFS – P2VP. We focus on the correlation
between mechanical properties and structures of all investigated thin films. In
particular, we combine in-situ mechanical measurements with XRR or BAM.
Mélanie Arangalage
1st year PhD Student at ESPCI Paris
10 Rue Vauquelin
75005 Paris
+33 (0)633598211
Boiling and aphroicity of oil mixtures
Abstract :
We study the stability and the breaking of oil foams and more precisely the role of
asphaltenes in their stability. Asphaltene are molecular substances that are found in crude
oil and that are known to cover gaz/oil interfaces making them rigid. Thus asphaltenes form
very stable foams which are difficult to break afterwards and the dynamics of this crust
formation plays a determining role on the foam stability. In order to detect this “skin”
formation, we set up experiments using Marangoni effect generated by concentration
gradient.
Density Functional Theory of a Curved Liquid-Vapour Interface
E. M.Blokhuis Universiteit Leiden, The Netherlands
It is argued that to arrive at a quantitative description of the surface tension of a liquid drop as a function of its inverse radius, it is necessary to include the bending rigidity k and Gaussian rigidity in its description. New formulas for k and in the context of density functional theory with a non-local, integral expression for the interaction between molecules are presented. These expressions are used to investigate the influence of the choice of Gibbs dividing surface and it is shown that for a one- component system, the equimolar surface has a special status in the sense that both k and are then the least sensitive to a change in the location of the dividing surface. Furthermore, the equimolar value for k corresponds to its maximum value and the equimolar value for corresponds to its minimum value. An explicit evaluation using a short-ranged interaction potential between molecules, shows that k is negative with a value around minus 0.5-1.0 kBT and that is positive with a value which is a bit more than half the magnitude of k. Finally, for dispersion forces between molecules, we show that a term proportional to log(R)/R2 replaces the rigidity constants and we determine the (universal) proportionality constants.
Ultrafiltration of charge-stabilized suspensions: Theory and experiment
Mariano Brito, Jonas Riest, Rafael Roa and Gerhard Nägele
Institute of Complex Systems, ICS-3 Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
E-mail: [email protected]
We present a comprehensive theoretical-experimental study of cross-flow membrane ultrafiltration (UF) [1] of aqueous suspensions of charge-stabilized colloidal particles [2,3]. Charge-stabilized dispersions exhibit interesting static and dynamic behavior, reflected in properties such as the osmotic pressure, collective diffusion coefficient and suspension viscosity. These properties are determined by electro-steric and electro-hydrodynamic interactions. We employ a Poisson-Boltzmann cell model in combination with integral equation theory for calculating the effective colloid pair potential, osmotic pressure and the colloid pair correlation functions. The latter are used as input in our calculation of the concentration-dependent collective diffusion coefficient and viscosity that are essential ingredients to the modeling of the convective-diffusive transport in the filtration process. The efficiency of the separation process depends on hydrodynamic boundary conditions, membrane properties and particle interactions. We calculate the particles concentration polarization layer at and the permeate flux through the filter membrane, and the threshold for the onset of membrane cake formation. The theoretical predictions are compared with UF experiments on aqueous low-salinity suspensions of charged silica spheres. The predicted dominance of collective back diffusion away from the membrane surface is quantitatively confirmed by the experiment [2]. References
[1] R. Roa, E.K. Zholkovskiy and G. Nägele, Soft Matter 11, 4016 (2015) [2] R. Roa, D. Menne, P. Buzatu, J. Riest, J.K.G. Dhont, E.K. Zholkovskiy, M. Wessling
and G. Nägele, Soft Matter, DOI: 10.1039/c6sm00660d (2016) [3] M. Brito, J. Riest and G. Nägele, work in progress
Crystallization of PEO at the air-water interface Karsten Busse, Christian Fuchs, Jörg Kressler Martin-Luther-Universität Halle-Wittenberg
After spreading on the water surface some polymers can form stable, compressible monolayers. Hydrophilic PEO of molar mass >2000 g/mol also forms a stable monolayer but when compressed the polymer dissolves in the water subphase at a surface pressure ~ 10 mN/m. However, if a salt is added to an aqueous PEO solution the polymer precipitates. The salting-out effect of different cations and anions is displayed in the Hofmeister series, which is primarily known for studies involving proteins. We recently showed that by addition of potassium carbonate K2CO3 to an aqueous subphase at a concentration above 2 mol/L PEO remains on the water surface and forms a monolayer which is stable towards much higher surface pressures.i The formation of crystalline structures were observed by Brewster Angle Microscopy (BAM) and GIWAXS when the isotherm reached a pseudo-plateau at higher surface pressures (see Fig. below).These structures resemble crystalline PEO in ultrathin filmsii. In thin films of PEO on solid supports transferred from surface of the aqueous salt solution by the Langmuir Blodgett technique both the polymer and the salt were present so an X-ray analysis of these films is difficult. Infrared reflection absorption spectroscopy (IRRAS) can be used to study rearrangement processes during a transition in a Langmuir film of a polymeriii.
i Fuchs, C.; Hussain, H.; Amado, E.; Busse, K.; Kressler, J. Macromol. Rapid Commun. 2015, 36, 211. ii Braun, H.-G.; Meyer, E. Int. J. Mol. Sci. 2013, 14, 3254. iii Fuchs, C.; Hussain, H.; Schwieger, C.; Schulz, M.; Binder, W. H.; Kressler, J. J. Colloid Interface Sci. 2015, 437, 80.
a) b)
a) Langmuir isotherm of PEO Mn = 106.500 g/mol on pure water and a aqueous salt solution of 2 mol/L K2CO3
b) BAM images of the growth of crystalline domains in Langmuir film of the same PEO on a 4 mol/L K2CO3 aqueous salt solution
Coalescence of particle-‐stabilized droplets using microfluidics
Greet Dockx1, Paula Moldenaers1, Jan Vermant2
1. Soft Matter Rheology and Technology, Department of Chemical Engineering, KU Leuven, W. de Croylaan 46, Heverlee, Belgium
2. Department of Materials Science, ETH Zurich, Switzerland
Email: [email protected] Coalescence is a major issue for the stabilization of emulsions. It is known, in qualitative terms, that this important morphology-‐controlling event can be substantially affected by interfacial rheology. In this work we study coalescence of oil/water droplets, with interfaces of known interfacial rheological behavior. There are a number of experimental problems that occur in bulk, low viscous emulsions that need to be resolved before embarking on a systematic study. First of all, creaming or sedimentation can hinder coalescence or deformation experiments. Secondly, in simple shear and extensional flows, very high shear rates are required for break-‐up or even for obtaining a considerable deformation in such low bulk viscosity materials. To overcome these problems, specific microfluidic setups were designed and manufactured. To create droplets and bubbles, T-‐junction and flow-‐focusing geometries were developed. The coating of droplets with various classes of stabilizers, with distinct interfacial rheological properties, is investigated. We succeeded in making protein and surfactant stabilized droplets, but it remains however a challenge to create controllable particle-‐laden droplet interfaces. Since in a microfluidic device one droplet is precisely fabricated at a time, we try to optimize the design of a microfluidic chip for producing individual droplets with well-‐controlled particle-‐laden droplet interfaces. These droplets can then be investigated in coalescence geometries in which a wide range of deformation/approaching speeds is possible for a pair of droplets. This will give insight on the direct effect of the interfacial rheological properties on coalescence stability, allowing engineering guidelines for the selection or development of the optimally performing interfacial stabilizers.
Cationic Hofmeister Series of Wettability in Mica-Water-Alkane Systems B. Bera, N. Kumar, M.H.G. Duits, M.A. Cohen Stuart, D van den Ende & F. Mugele. Abstract The specific interaction of ions with macromolecules and solid-liquid interfaces is of crucial importance to many processes in biochemistry, colloid science and engineering, as first pointed out by Hofmeister in the context of (de)stabilization of protein solutions. Here, we use contact angle goniometry to demonstrate that the macroscopic wettability of aqueous salt solutions of variable pH on mica immersed in ambient alkane, increases from near-zero contact angles to values exceeding 10o, depending on the specific cation. This results in a series of increasing power to induce partial wetting in the order: Na+; K+ < Li+ < Rb+ < Cs+ < Ca2+ < Mg2+ < Ba2+, very similar to the direct Hofmeister series for proteins. Complementary Atomic Force Microscopy measurements show that charge reversal of the mica-electrolyte interface promotes finite contact angles but is not a necessity. Together with the strong impact of Li+ and Mg2+ ions, this demonstrates that non-electrostatic effects play an important role for the observed wettability alteration.
Hydration lubrication in polymeric thin layers Noa Iuster, Nir Kampf, Ronit Goldberg, Jacob Klein
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel.
Hydration lubrication is a boundary lubrication mechanism which is responsible for the
extremely efficient lubrication seen in hydrated systems such as atomically smooth
surfaces across salt solutions or between surfaces bearing hydrated polymer brushes and
liposomes.
pHEMA was the first hydrogel synthesized for biomedical purposes and it is widely used
in biomedical devices and applications.
In this study. we wish to understand how pHEMA interacts with the lipid vesicles. Using
AFM and SFB we observed that the presence of the pHEMA on the surface, prior to the
adsorption of liposomes, reduces their stability on the surface and leads to their rupture.
However, the presence of the lipids on the pHEMA surface leads to a significantly
improved lubrication, most likely due to lipid-pHEMA complexation and the resulting
exposure of highly hydrated phosphocholine groups.
Lubrication Between Hydrophobic and Hydrophilic Surfaces Across Aqueous Solutions
Irit Rosenhek-Goldian*, Nir Kampf*, Jacob Klein
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
Friction between hydrophobic and hydrophilic surfaces in aqueous media can occur in systems like artificial implants, contact lenses, etc. However its mechanism is not well understood. We measure directly both normal forces and sliding friction in an aqueous environment between a mica (negatively-charged hydrophilic surface) and a stable, smooth, highly hydrophobic surface (fluoropolymer film), using a surface force balance. Normal-force vs. surface-separation profiles indicate a high negative charge density on the hydrophobic surface, in line with previous studies and attributed to adsorbed –OH- ions. Sliding of the compressed surfaces under water or in salt solution reveals remarkably low friction (friction coefficient ≈ 0.003 – 0.009) up to contact pressures of at least 50 atm. This is attributed to hydration lubrication mediated by hydrated counterions trapped between the surfaces. Our results show that efficient lubrication can occur uniquely at a hydrophobic-hydrophilic interface under water.
*equally contributors
Electrochemical synthesis of sp2 carbon films on zinc from polysaccharide and gelatin thin
film precursors
Ksiazkiewicz Agnieszka,1 Fernandez Solis Christian,1 Erbe Andreas 1 ,2
1 - Max-Planck-Institut für Eisenforschung GmbH, Department of Interface Chemistry and
Surface Engineering, Düsseldorf, Germany
2 - Norwegian University of Science and Technology, Department of Materials Science and
Engineering, Trondheim, Norway
Materials based on sp2 carbon have received significant attention in recent years, amongst others
as electrocataysts. This work presents the in situ preparation of thin sp2 carbon films from
biopolymer precursors on metallic zinc. During the exposure of the 50-70 nm thick precursor
films which were prepared by spin-coating to a sufficiently large electrode potential range in
0.1M KCl, black layers were formed on the zinc substrate. A black color developed when bare
zinc substrate as well as polymer coated zinc were exposed to sufficiently negative as well as
sufficiently positive potentials from the open circuit potential (OCP). After spectroscopic
characterization, it was confirmed that electrochemical treatment induced carbon formation from
the polymers as well as ZnO formation. Raman spectroscopy showed clear peaks at around 1355
and 1590 cm-1 corresponding to graphitic sp2 hybridized carbon and disappearance of initial
polymer peaks. The lack of G’ band in graphite at around 2700 cm-1 indicates amorphous nature
of generated carbon species. The highest intensity of carbon deposition occurred for modified
gelatin coating which in the presence of thicker coating layer exhibited interesting behavior
where darkening of the sample was reversible in a reproducible way, depending on potential
applied. Successfully deposited carbon was tested as a catalyst for oxygen evolution reaction
(OER) and oxygen reduction reaction (ORR). Further work shall clarify the reaction pathway
from saccharides to sp2 hybridized carbon. The formed ZnO/sp2 carbon structures may have
interesting catalytic or electric properties.
TITLE: Coalescence Inhibition through Asphaltene Adsorption
Authors: Maria Consiglia Merola1, Simone Bochner2, Gerald Fuller2, Dimitris Vlassopoulos1
1. FORTH, Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece
2. Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
Asphaltenes – which are defined as the crude oil fraction soluble in toluene and insoluble in n-heptane –
can negatively affect oil and water separation processes. Those polar macromolecules are surface-active
and may aggregate at the oil/water interface forming a solid-like layer that hinders coalescence. This
effect can cause several technical issues during production and refining of crude oils. To attain adequate
export oil quality is essential to have a successful oil/water separation process. To this aim we
conducted a fundamental study of effects of asphaltene aggregation at the oil/water interface on
coalescence inhibition.
First, we investigated the behavior of asphaltenes at the water/air interface by compression/expansion
cycles in a Langmuir-Blodgett trough. Results show a pronounced hysteresis during the first
compression/expansion cycle. This hysteresis decreases when a second cycle is performed. This result
can be interpreted assuming that the asphaltenes initially flat at the interface, and then tilt irreversibly
upon compression. Moreover, we observed a transition from a two-dimensional to a three-dimensional
configuration of the asphaltenes at the interface.
Also, interfacial rheology studies were performed in a stress-control rheometer equipped with a double-
wall ring geometry. Results show that the water/air interface presents solid-like behavior due to the
presence of asphaltenes. Furthermore, higher asphaltene concentration yields higher elasticity due to a
cross-linked network structure.
Using a newly developed apparatus, we performed a study of single water droplet coalescence and film
drainage at water/oil interfaces; the oil phase consists of a model oil solution of asphaltenes in toluene.
We investigated the influence of aging time on coalescence, where both interfaces (water droplet and
water/oil interfaces) were symmetrically aged. In addition, the role of asphaltene concentration in the
oil phase was analyzed. Results show that higher concentrations yield dramatically longer coalescence
times. Similarly, longer interface aging results in longer coalescence times at fixed concentrations. These
coalescence results are in good correspondence with the interfacial rheology findings.
Surface Rheology of Block-Copolymer Stabilized Interfaces
Ahmad Moghimikheirabadi1, Leonard M. C. Sagis1, 2 and Patrick Ilg3 1ETH Zürich, Department of Materials, Polymer Physics, CH-8093 Zürich, Switzerland
2Food Physics Group, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands
3School of Mathematical and Physical Sciences, University of Reading, Reading RG6 6AX, United Kingdom
Complex fluid-fluid interfaces are interfaces in which the adsorbed species self-assemble into complex microstructures. These interfaces can be formed by a wide range of surface active components, such as proteins, colloidal particles, polymers, lipids, or mixtures of these components [1]. In this study, our goal is to characterize the microstructure and mechanical properties of fluid-fluid interfaces stabilized by multi-block copolymers, using a multiscale multidisciplinary approach, which integrates state of the art computational methods, surface rheological and interfacial structure evaluation experiments and non-equilibrium thermodynamics. Using Monte Carlo (MC) and non-equilibrium molecular dynamics (NEMD) simulations, surface microstructure, surface rheological properties, and the surface free energy in terms of a set of structural variables can be obtained. Various methods of microscopy (such as AFM, SEM and TEM) and also reflectivity measurements (X-ray and neutron) can be used for evaluating the microstructure of the interface and by employing large amplitude oscillatory shear and dilatation measurements, the nonlinear response of copolymer stabilized interface can be characterized. Using the results from both experiments and computer simulations as a starting point, we will develop nonlinear coarse-grained constitutive models in the GENERIC [2] framework, able to describe the stress response and structural evolution of the interface as a result of an applied deformation. We will determine the mechanical properties and interfacial structure as a function of surface polymer concentration, chemical structure of the polymers (variation of number, size, and distribution of blocks) and degree of hydrophobicity and rigidity of the sub-blocks. In this study, we investigate the liquid-vapor diblock copolymer stabilized interface by using MC simulations. The coarse-grained system consists of Lennard-Jones solvent molecules and bead-spring diblock copolymers which are initially placed at the liquid slab portion of the simulation box. Adsorption and surface tension isotherms, solvent and diblock copolymer density profiles, diblock copolymer radius of gyration distributions, end to end vector, and some other structural properties of the diblock copolymers at the liquid-vapor interface are extracted from this simulation. Figure 1 represents a sample configuration of the system after reaching equilibrium.
Figure 1. A snapshot of the system configuration after reaching equilibrium. The system consists of 75A4B6 block-copolymers and
5040 solvent molecules. The red spheres stand for hydrophobic beads (B), the blue spheres stand for hydrophilic beads (A) and the
yellow spheres stand for solvent particles.
[1]. Sagis LMC, Reviews of Modern Physics 83 1367 (2011). [2].Grmela M, Öttinger HC, Phys. Rev. E. 56 6620 (1997).
Abstract SOMATAI 2016
Interfacial forces and solvation on Nafion® membrane model systems with varying hydrophobicity
L. Moreno Ostertag1, X. Ling2, S. H. Parekh2, K. F. Domke2, T. Utzig1, P. Stock1, M. Valtiner1* 1Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany. 2Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany.
*Author to whom correspondence should be addressed: [email protected] (M. Valtiner)
Adhesive forces between two surfaces can be studied as single-molecule phenomena as well as a macroscopic property. Both Atomic Force Microscopy (AFM) and Surface Forces Apparatus (SFA) can give great insights into the world of surface interactions1, 2 by studying the binding between molecules attached to these areas via functionalization.3 AFM provides a scheme for the detection of single molecule interactions, while SFA allows probing situations where billions of molecules interact simultaneously. In the frame of these techniques, the interaction forces between the sulfonic groups inside of Nafion® membranes are emulated via self-assembly monolayers (SAM) and then analyzed as SO3
- is gradually substituted by hydrophobic groups under different pH conditions. The resulting interaction profiles can be fitted to diverse models depending, for instance, on hydrophobic or ionic content, in order to gain insight into the type and magnitude of these forces.
References
1. Raman, S.; Utzig, T.; Baimpos, T.; Ratna Shrestha, B.; Valtiner, M., Deciphering the scaling of single-molecule interactions using Jarzynski’s equality. Nat Commun 2014, 5. 2. Stock, P.; Utzig, T.; Valtiner, M., Direct and quantitative AFM measurements of the concentration and temperature dependence of the hydrophobic force law at nanoscopic contacts. Journal of Colloid and Interface Science 2015, 446, 244-251. 3. Valtiner, M.; Donaldson, S. H.; Gebbie, M. A.; Israelachvili, J. N., Hydrophobic Forces, Electrostatic Steering, and Acid–Base Bridging between Atomically Smooth Self-Assembled Monolayers and End-Functionalized PEGolated Lipid Bilayers. Journal of the American Chemical Society 2012, 134 (3), 1746-1753.
Co-non-solvency phenomena in bulk and adsorbed smart polymer solutions
Debashish Mukherji, Kostas Ch. Daoulas, and Kurt KremerMax-Planck Institut fur Polymerforschung, Ackermannweg 10, 55128 Mainz Germany
Smart polymers are a modern class of soft materials that show drastic changes in their physical properties by aslight change in external stimuli [1]. One such phenomenon is known as co-non-solvency. Co-non-solvency occurswhen a polymer is added to a mixture of two (perfectly) miscible and competing good solvents. As a result, the samepolymer collapses into a globule within intermediate mixing ratios [2]. More interestingly, polymer collapses when thesolvent quality remains good or even gets increasingly better by the addition of the better cosolvent [3]. This puzzlingphenomenon, where the solvent quality is completely decoupled from the polymer conformation, is driven by stronglocal preferential adsorption of better cosolvent with the polymer [3,4]. Because a polymer collapses in good solvent,the depletion forces, that are responsible for poor solvent collapse, do not play any role in describing co-non-solvency[5].
In this work, we will present a universal (generic) picture of co-non-solvency phenomenon by combining computersimulations and theoretical arguments. Furthermore, we will discuss how does this co-non-solvency picture correlateswith behavior of polymers adsorbed on surfaces in the presence of mixed solvents.
References:
[1] M. A. Cohen-Stuart, et al. Nature Materials 9, 101 (2010).[2] D. Mukherji and K. Kremer, Macromolecules 46, 9158 (2013).[3] D. Mukherji, C. M. Marques, and K. Kremer, Nature Communications 5, 4882 (2014).[4] D. Mukherji, C. M. Marques, T. Stuehn and K. Kremer, Journal of Chemical Physics 142, 114903 (2015).[5] T. E. de Oliviera, P. A. Netz, D. Mukherji, and K. Kremer, Soft Matter 11 8599 (2015).
Effect of competing short-range attraction and long-rangerepulsion on the dynamics of globular particle dispersions
Jonas Riest and Gerhard NägeleForschungszentrum Jülich GmbH, Institute of Complex Systems (ICS-3),
D-52425 Jülich, GermanyE-mail: [email protected]
The dynamic clustering of globular particles in suspensions exhibiting competing short-range
attraction and long-range repulsion such as in protein solutions has gained a lot of interest over
the past years. We investigate theoretically the influence of clustering on the dynamics of globu-
lar particle dispersions [1]. To this end, we systematically explore various pair potential models
by a combination of state-of-the-art analytic methods in conjunction with computer simulations
where the solvent-mediated hydrodynamic interactions are likewise included. Our results show
that the cluster peak (intermediate-range-order peak) is present also in the hydrodynamic func-
tion characterizing the short-time dynamics. Enhanced short-range attraction leads to a smaller
self-diffusion coefficient and a larger dispersion viscosity. The behavior of the (generalized)
sedimentation coefficient is more intricate depending on the selected interaction parameters.
Our results are relevant also for technological applications, such as the ultrafiltration of pro-
teins.
[1] J. Riest and G. Nägele, Soft Matter, 11, 9273-9280 (2015)
Molecular Simulations of flower-like micelles and
micellar gels
Lucie Nová,∗ Filip Uhlík, and Peter Košovan
Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles
University in Prague, Hlavova 8, 128 00 Praha 2, Czech Republic
E-mail: [email protected]
The aim of this work is to study the system which may form flower-like micelles or
micellar gel by means of Hybrid Monte Carlo simulations in the reaction ensamble. The
block-copolymers used in these simulations constitute of 3 parts of the same length: 20
beads with hydrophobic modifications - 20 polyelectrolyte beads - 20 beads with hydrophobic
modification. We put 20 chains in the box.
The system parameters which were tuned are: concentration (box size), KA of the poly-
electrolyte tail (i.e. pH), ionic strength (adding salt).
We simulated the above described system at concentrations range from 0.1 mg/ml to 10
mg/ml (assuming that the monomer units are P2VP). At the lowest concentration, the chains
were independent. Then, with increasing concentration, the chains formed first individual
loops, which further formed micelles and bridges. Gelation was observed above 5 mg/ml. KA
was swept from 10−10 (not dissociated at all, neutral chain) to KA=10−1 (charged chain). We
added monovalent salt. By means of increasing the ionic strength, intramolecular connections
(loops, micellization) are preferred prior to the intermolecular connections (bridges, gelation).
∗To whom correspondence should be addressed
1
Formation of polyelectrolytes shells on nanogels surfaces
K. Podgórna, K.Szczepanowicz, P. Warszyński J. Haber Institute of Catalysis and Surface Chemistry PAS
Niezapominajek 8, 30-239 Krakow, Poland Polysaccharides nanogels belong to a rapidly growing group of materials, which can find various applications not only in the food industry but also in medicine, pharmacy or agriculture. They are characterized by a unique combination of hydrogel properties (hydrophilicity, elasticity, high water content) with nanometer size. One of the most interesting materials for nanogel forming is alginate as it forms stable networks in a simple, one-step gelation process. By adsorption of charged species (e.g. polyelectrolytes, magnetic particles) on nanogels surfaces new materials with desirable properties can be obtained.
Formation of polyelectrolytes shells on nanogels surface and investigation of properties of the resulting nanocapsules was the aim of this study. Calcium-alginate nanogels were prepared by using water in oil (W/O) microemulsions. Prepared nano-beads were purified from toxic components and charazterized by: Dynamic Light Scattering (DLS), Cryo-Scanning Electron Microscopy and microelectrophoresis. Moreover, surface of obtained nanogels were modified by the layer by layer (LbL) technique with synthetic (Poly-L-lysine hydrobromide PLL(+), Poly-L-glutamic acid sodium salt PGA (-)) and natural polyelectrolytes (Chitosan CHI (+), Sodium Alginate ALG (-)) or iron oxide nanoparticles. Stability of such non-modified and modified nanogels was investigated.
Transition from Wet to Dry Friction
Alexander Schlaich, Julian Kappler, Roland R. Netz
Department of Physics, Free University of Berlin, 14195 Berlin, Germany
The dynamics and shear properties of nanoconfined aqueous systems are of great interest for
biolubrication and nanotribology. The properties of confined water under ambient conditions
are critical in biological situations, as for example in synovial joints, but also for transport
properties in water slabs and channels.
The recently developed thermodynamic extrapolation technique[1,2] enables us to study the
molecular details of the relation between friction and load at the transition between wet and
dry lubrication.
For biologically relevant hydrophilic surfaces we find slip boundary conditions for the water
flow at sub-nanometer confinement, whereas for larger distances no slip is observed. We
further describe a continuum model for the local viscosity which explains the simulation
results.
References:
[1] E. Schneck, F. Sedlmeier, and R. R. Netz, “Hydration repulsion between biomembranes results from an
interplay of dehydration and depolarization,” PNAS, vol. 109, no. 36, pp. 14405–14409, Sep. 2012.
[2] A. Schlaich, B. Kowalik, M. Kanduč, E. Schneck, and R. R. Netz, “Simulation Techniques for Solvation-
Induced Surface-Interactions at Prescribed Water Chemical Potential,” in Computational Trends in Solvation and
Transport in Liquids, vol. 28, G. Sutmann, J. Grotendorst, G. Gompper, and D. Marx, Eds. Jülich:
Forschungszentrum Jülich GmbH, 2015, pp. 155–185.
Figure 1: Steady state shearing between two hydrophilic surfaces.
Title: New food emulsions stabilised by submicron-scale lipid particles
Name: Anja Schröder
Supervisors: Claire Berton-Carabin (dr.), Joris Sprakel (dr.), Karin Schroën (prof).
New food emulsions stabilised by lipid nanoparticles
In many food products oil droplets are dispersed in an aqueous phase, i.e. an oil-in-water (O/W)
emulsion. Physical stability of emulsions is generally achieved by the adsorption of amphiphilic
molecules (e.g. proteins or surfactants), although only to a certain extent since emulsions are
thermodynamically unstable systems. An additional concern is the chemical instability of food
emulsions, especially when considering oils containing polyunsaturated fatty acids (PUFAs) that
provide beneficial health effects, but readily oxidise and loose consumer acceptance.
In industrial products, lipid oxidation is ‘controlled’ by antioxidants (e.g. tocopherols). However, these
components are highly hydrophobic and therefore located anywhere in the oil phase. Lipid oxidation is
presumably initiated at the interface, so it would be beneficial to locate the antioxidant right there.
This project focusses on the development of physically and chemically stable food emulsions
containing high levels of PUFAs and low levels of (synthetic) antioxidants based on a novel colloidal-
scale design using antioxidant loaded submicron lipid particles adsorbed at the oil-water interface to
provide physical stability (Pickering emulsion) and influence chemical destabilisation. With this novel
dual approach we strive to develop a new generation of food emulsions.
Title: “Acrylic polymers at fluid interfaces” Authors: Maria Sevastaki1, 2, Benoit Loppinet1, Dimitris Vlassopoulos1, 2, Joseph Samaniuk3, Jan Vermant3 1FORTH, Institute of Electronic Structure and Laser, Heraklion, Crete 70013, Greece 2University of Crete, Department of Materials Science & Technology, Heraklion, Crete 71003, Greece 3ETH, Department of Materials, 8093 Zurich, Switzerland Abstract This work focuses on the structural and rheological properties of viscoelastic films at the air-water interface using a Langmuir trough. The techniques used include compression-expansion cycles and rheology by means of the magnetic rod interfacial stress rheometer. Our aim was to understand the relation between the macromolecular conformation and interfacial properties. To this end we used well- characterized samples of acrylic polymers of varying molecular weights and molecular structure, Poly (methyl methacrylate), PMMA atactic, syndiotactic, dendritic and Poly (n - butyl acrylate) PBA linear, star). We discuss the experimental results in terms of film reversibility and viscoelastic properties. We attempt at assessing our findings in view of molecular characteristics as well as the spreading procedure (given the difference in glass transition temperature of bulk PMMA and PBA) and the available information in the literature.
Correlation Ellipsometry
Reinhard Sigel
German University in Cairo (GUC), Egypt
The polarization optics minimization procedure of nulling ellipsometry isapplied to correlation functions measured by dynamic light scattering (DLS), inorder to measure dynamics at interfaces.
The goal of this conceptual study is to develop a measurement procedureto capture interfacial dynamics with ellipsometry resolution. In the classicaldescription of reflection ellipsometry, the polarization optics minimization ofthe measured intensity yields the complex ratio rp/rs = tan(Ψ) exp[i∆] of theamplitude reflection coefficients rp, and rs in p and s polarization, respectively[1]. The ratio is usually expressed in terms of the ellipsometry parameterstan(Ψ) and ∆. In a similar way, scattering ellipsometry [2] or ellipsometriclight scattering [3] measure the complex ratio S2/S1 of the scattering coeffi-cients S2 and S1 for two orthogonal polarization modes of light. An improveddescription of ellipsometry which allows for the distinction of coherent and in-coherent effects as well as for smearing effects relies on the averages 〈S1S
∗1 〉,
〈S2S∗2 〉, and 〈S1S
∗2 〉, which are connected to the Stokes parameters and thus
are experimental accessible [4]. A generalization of these averages are the fieldcorrelation functions 〈S1(t′)S∗1 (t′ + t)〉t′ , 〈S2(t′)S∗2 (t′ + t)〉t′ , 〈S1(t′)S∗2 (t′ + t)〉t′ ,and 〈S2(t′)S∗1 (t′ + t)〉t′ , which determine polarization dependent DLS with ellip-sometry polarization optics. DLS most often is described as an auto correlationfunction of the scattered electrical field; this auto correlation function is di-rectly connected to the mentioned auto correlation functions of the scatteringcoefficients [5].
Starting point for the description is a common distribution function for thetwo fluctuating scattering coefficients S1(t) and S2(t), which contains their timeauto and cross correlation functions. Based on Gaussian statistics, an equationsimilar to the Siegert relation for any ellipsometry polarization is derived. For apolarization setting where not exclusively S1(t) or S2(t) are selected, the equa-tion for the intensity correlation function contains all field correlation functionslisted above. A simplification is based on ellipsometric minimization for anycorrelation time t of the correlation functions. The result are the ellipsometricparameters tan(Ψ(t)) and ∆(t) as a function of t. Ongoing work concerns theconnection of these functions to interface dynamics.
[1] R.M.A. Azzam and N.M. Bashara, Ellipsometry and Polarized Light(Elsevier, 1977).
[2] Th. A. Germer, Phys. Rev. Lett. 85, 349 (2000).[3] A. Erbe, K. Tauer, R. Sigel, Phys. Rev. E 73, 031406 (2006).[4] R. Sigel, A. Erbe, Appl. Opt. 47, 2161 (2008).[5] D. J. Ross, R. Sigel, Phys. Rev. E 85, 056710 (2012).
Influence of the surface properties of colloidal poly(ε-caprolactone) nanospheres on its stability in bio-fluids
M. Szczęch, M. Piotrowski, K. Szczepanowicz, P. Warszynski.
Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow, Poland, [email protected];
Poly(ε-caprolactone) (PCL) is biodegradable, biocompatible and water insoluble polymer widely used in different drug delivery systems as nanospheres, microspheres or implants. Compared to other polymers, PCL characterizes slow degradation time that makes it suitable for long-term delivery systems. Due to the slow degradation of the PCL, it’s important to extend its circulation time in the body fluids by e.g. appropriate modification of its surface properties that may leads to increase the PCL nanospheres stability. It may be achieved through modification of PCL-based carriers surface such as by immobilization of poly(ethylene glycol) (PEG).
In this work we were focused on preparation of PEGylated-PCL nanospheres using low-energy emulsification method. The PCL-modified nanocarriers were synthesized from nanoemulsions by phase inversion composition method (PIC) and were characterized by size, size distribution, zeta potential and imaged by SEM. Biocompatibility tests and stability in the simulated body fluids was also determined. Initial test of protective action of selected neuroprotectants encapsulated in PCL-nanospheres were performed.
Acknowledgements: The research leading to these results was supported by the Norwegian Financial Mechanism grant Pol-Nor/199523/64/2013 “NanoNeucar” and M. Smoluchowski scholarship, KNOW.
Pegylated polyelectrolyte multilayer films as the “antifouling” coatings protecting against non-specific proteins adsorption
Szczepanowicz, K.; Kruk, T.; Warszyński, P.
Jerzy Haber Institute of Catalysis and Surface Chemistry PAS,
Niezapominajek st. 8, 30-239 Krakow, Poland
A variety of biomedical devices and drug delivery systems are used in direct contact with biological fluids. There are a number of problems associated with such use of materials. One of the most significant is associated with the fact that on the surfaces exposed to solutions containing biological material the process of biofouling occurs. Immobilization of neutral hydrophilic polymers (e.g. poly(ethylene glycol) (PEG)) at surfaces is one of the promising methods to reduce non-specific adsorption of proteins.
The aim of our work was to developed method for direct immobilization of PEG layer to reduce/eliminate non-specific adsorption of proteins at surface of polyelectrolyte multilayer thin films formed by the „LbL” method. Synthesized copolymers of poly(glutamic acid) or poly(L-lysine) with grafted PEG chains with various grafting ratio and various chain lengths, were used for that modification by formation of the external pegylated layer of films. The biofouling process was investigated by studying the adsorption of different proteins; HSA (Human Serum Albumin), Fibrinogen and Human Serum using Quartz Crystal Microbalance (QCM). Additionally synthesized pegylated copolymers were used to modify polyelectrolyte nanocapsules. Such pegylated nanocapsules were characterized by size, size distribution, zeta potential and imaged by SEM. Biocompatibility tests and stability in the simulated body fluid/cell culture medium ass determined.
Acknowledgements: The work was financed by NCN project UMO 2011/03/D/ST5/05635
SUPRAMOLECULAR PICKERING EMULSIONS
N. Vilanova1, A. Aloi1, I. K. Voets1, 2, 3
1Laboratory of Macromolecular and Organic Chemistry, Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands
2Laboratory of Chemical Biology, Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands
3Laboratory of Physical Chemistry, Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands
Pickering emulsions are emulsion stabilized by particles instead of surfactants. Due to the high
attachment energy of the particles at the droplet interface, Pickering emulsions offer a higher stability
compared to the conventional surfactant-stabilized emulsions, especially in terms of droplet coalescence.
The fact that particles are used as stabilizers offers an extra advantage, as interesting properties can be
endowed to the system by using functional particles with optic, magnetic or catalytic properties. The aim
of this study is to form Pickering emulsions using supramolecular colloids as stabilizers. Such
supramolecular colloids consist of silica colloids functionalized with a benzene-1,3,5-tricarboxamide
(BTA) derivative. Such BTA molecules recognize and selectively interact with identical BTAs through 3-
fold intermolecular hydrogen bonds [1]. The BTA can also be equipped with a photo-cleavable group to
block the formation of the hydrogen-bonds when present. Studies on the behaviour of these colloids in
cyclohexane showed that prior to irradiation, BTA-colloids remain as singlets. Interestingly, upon
cleavage of the protective group by light, colloids cluster as the short-range hydrogen-bonding interactions
between anchored molecules are activated [2]. To use these colloids as emulsion stabilizers, firstly, their
hydrophobicity was tuned to obtain the appropriate contact angle to be able to stabilize water-in-
cyclohexane emulsions. Secondly, formulation studies were carried out changing the amount of particles
as well as the water/cyclohexane ratio to obtain stable Pickering emulsions. Finally, the behaviour of the
supramolecular Pickering emulsions upon irradiation was studied by means of confocal microscopy.
[1] T. F. A. de Greef, E. W. Meijer, Nature, 453, 171-173, 2008
[2] I. de Feijter, L. Albertazzi, A. R. A. Palmans, I. K. Voets, Langmuir, 31, 57-64, 2015
Nano-structures mediated assembly of small molecules and polymers
Rachel Yerushalmi - Rozen
Dept. of Chemical Engineering &
Ilze Katz Institute for Nanoscale Science &Technology Ben-Gurion University of the Negev, Israel
The effect of embedded nano-structures on the self-organization and ordering of a host media
of self-assembling molecules has been demonstrated in a few systems. Observations
accumulated over the last two decades indicate that embedded nano-structures may affect the
phase diagram of the host material, shift the onset of micellization, the liquid-liquid phase
transition, induce polymer crystallization and more. Rationalization of the observed behaviors
indicates that the relevant mechanisms are fundamentally different from those predicted by
classical colloidal theories. In my talk I will describe experimental studies of a few examples
investigated by us over the last years, where nano-structures induce self-assembly in a
surfactant phase, modify the phase diagram of an amphiphilic polymer in an aqueous media,
and nucleate the crystallization of conjugated polymers.
1. Itzhak-Cohen, R. et. al "Nematic Ordering of SWNT in Meso-Structured Thin Liquid Films of Polystyrenesulfonate" Langmuir, 2014, 30, 14963−14970.
2. Shvartzman- Cohen, R.; Monje, I.; Florent, M.; Fridman, V.; Goldfarb, D.; Yerushalmi – Rozen, R MACROMOLECULES, 2010, 43 (2), pp 606–614.
3. Ben-David, O.; Nativ-Roth, E.; Yerushalmi-Rozen, R.; Gottlieb, M SOFT MATTER, 2009, 5, 1925 – 1930.
Polyurethane – Water Interfaces studied with Fiber Probes
Ruyi Zheng, Leon Bremer
Advanced Chemical Engineering Solutions (ACES), DSM, 6167 RD Geleen, Netherlands
Abstract:
Waterborne polyurethanes (WPU) are made by self-assembly of polyurethane (PU) oligomers in water.
This process is mostly affected by the amount of carboxylic groups in the PU that are the hydrophilic
parts of the amphoteric oligomers, especially after neutralization to anionic groups. There is a demand
for larger WPU particles and these could be obtained by reducing the amount of carboxylic groups or
the degree of neutralization. However, this usually prevents self-assembly leading to separate PU and
water rich phases. In some formulations the PU can be emulsified but such dispersions are very
dependent on the emulsification conditions and therefore hard to produce in a reproducible way.
Therefore we want to study the interfacial and bulk properties of WPU’s in more detail. A sensitive and
fast method using fiber probes was used in this paper to study the effect of the amount of carboxylic
groups in PU on physical properties. From the force felt by the probe while passing the interface it is
possible to obtain interfacial parameters like the interfacial tension and bulk parameters like the
rheology of the PU in contact with water. We use this technique on a series of model PU oligomers with
varying amount of carboxylic groups and try to relate these data to self-assembly or emulsification
properties.
