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COST Action Workshop CM 1101
WG 2 and WG 5
Interactions in Colloidal
Systems
TU Berlin
24. – 26. März 2014
ESF provides the COST Office through a European Commission Contract contract
COST is supported by the EU RTD Framework Programme
The Council of the European Union provides the COST Secretariat
Conference Venue
Technische Universität Berlin
Institut für Chemie
Room C 230
Straße des 17. Juni 135
10623 Berlin
Organizers
Prof. Dr. Regine v. Klitzing (Technische Universität Berlin), WG 2
Prof. Thomas Zemb (Institut de Chimie Séparative de Marcoule), WG 5
Prof. Epameinondas Leontidis (University of Cyprus), COCIS
Map
Der Workshop findet statt an der Technischen Universität Berlin, Institut für Chemie, C-Gebäude,
Raum C 230, Straße des 17. Juni 115 in 10623 Berlin
Abstracts – Talks
“Interactions in Colloidal Systems”
From hydration repulsion to hydrophobic attraction: what happens in between?
Roland Netz1* and Matej Kanduc1 and Emanuel Schneck2
1 Physics Dept. FU Berlin
2 Biomaterials Dept., MPI Colloids and Interfaces, Potsdam
* e-mail: [email protected]
The molecular layer of water molecules on surfaces, the so-called hydration layer, is important for a whole
number of properties of biological as well as technological surfaces. This is demonstrated with a few
combined theoretical/experimental examples:
- The hydrophobic attraction can be quantitatively explained with classical MD simulations including explicit
water. Both water structural effects and dispersion interactions contribute to this solvation attraction. [1]
- The so-called hydration repulsion between polar surfaces in water can be studied using a novel simulation
technique that allows to efficiently determine the interaction pressure at constant water chemical potential.
The hydration repulsion is shown to be caused by a mixture of water polarization effects and the desorption
of interfacial water. [2]
- For peptides adsorbing at surfaces, the adsorption strength depends crucially on the surface wetting
properties. For hydrophilic surfaces, the interaction tends to be repulsive, for hydrophobic surfaces, the
interaction is attractive. The microscopic mechanism behind this crossover is discussed. [3]
References:
[1] Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface and intrapeptide forces,
D. Horinek, A. Serr, M. Geisler, T. Pirzer, U. Slotta, S. Q. Lud, J. A. Garrido, T. Scheibel, T. Hugel, R. R. Netz, PNAS
105, 2842 (2008).
[2] Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization, E.
Schneck, F. Sedlmeier, R. R. Netz, PNAS 109, 14405 (2012)
[3] On the Relationship between Peptide Adsorption Resistance and Surface Contact Angle: A Combined
Experimental and Simulation Single-Molecule Study, N. Schwierz, D. Horinek, S. Liese, T. Pirzer, B.N. Balzer, T.
Hugel, R. R. Netz, JACS 134, 19628 (2012).
Balance of enthalpy and entropy in depletion forces: a possible link to hydration forces?
S. Sukenik
1, L. Sapir
1, D. Harries
1,*
1 Institute of Chemistry and The Fritz Haber Research Center,
The Hebrew University of Jerusalem, Israel
* e-mail: [email protected]
Solutes added to solutions often dramatically impact molecular processes ranging from the suspension or
precipitation of colloids to biomolecular associations and protein folding. Here we revisit the origins of the
effective attractive interactions that emerge between and within macromolecules immersed in solutions
containing cosolutes that are preferentially excluded from the macromolecular interfaces. Until recently,
these depletion forces were considered to be entropic in nature, resulting primarily from the tendency to
increase the space available to the cosolute. However, recent experimental evidence indicates the
existence of additional, energetically-dominated mechanisms. In this review we follow the emerging
characteristics of these different mechanisms. By compiling a set of available thermodynamic data for
processes ranging from protein folding to protein–protein interactions, we show that excluded cosolutes can
act through two distinct mechanisms that correlate to a large extent with their molecular properties. For
many polymers at low to moderate concentrations the steric interactions and molecular crowding effects
dominate, and the mechanism is entropic. To contrast, for many small excluded solutes, such as naturally
occurring osmolytes, the mechanism is dominated by favorable enthalpy, whereas the entropic contribution
is typically unfavorable. We discuss the available models for these thermodynamic mechanisms, and
comment on the possible link of the underlying exclusion forces to the hydration forces often observed
between water-macromolecule interfaces.
References:
[1] S. Sukenik*, L. Sapir*, D. Harries, Balance of enthalpy and entropy in depletion forces. Curr. Opin. Coll.
Sci. 18, 495-501 (2013).
Application of scanning methods to distinguish between entropy and enthalpy driven phase transitions
Vitaly Kocherbitov1*
1 Biomedical Science, Faculty of Health and Society, Malmö University, SE-205 06, Malmö, Sweden
* e-mail: [email protected]
All phase transitions can be divided into enthalpy and entropy driven. The driving forces of phase
transitions in aqueous soft matter systems can be resolved by applying scanning methods [1]. In particular,
three experimental methods – sorption calorimetry, differential scanning calorimetry and humidity scanning
quartz crystal microbalance with dissipation monitoring [2] can be applied to study driving forces of phase
transitions. Advantages and disadvantages of the methods are discussed. The driving forces of phase
transitions can be directly measured in sorption calorimetric experiments [3] or calculated using van der
Waals differential equation using experimental data obtained by other methods. The results of experimental
studies show that in surfactants and lipids systems the phase transitions to phases with higher curvature
are driven by enthalpy, while phase transitions to phases with lower curvature are driven by entropy [3].
References: [1] V. Kocherbitov. Current Opinion in Colloid & Interface Science 2013, 18, 510–516
[2] G. Graf, V. Kocherbitov. J.Phys.Chem.B. 2013, 117, 10017−10026
[3] V. Kocherbitov. J. Phys. Chem. B. 2005, 109, 6430-6435
Thermodynamics of micellization from heat capacity measurements
Bojan Šarac1*, Marija Bešter Rogač1 and Jurij Lah1
1 Faculty of Chemistry and Chemical Technology, Aškerčeva 5, SI-1000 Ljubljana
* e-mail: [email protected] Differential scanning calorimetry (DSC), the most important technique for studying thermodynamics of
structural transitions of biological macromolecules, is seldom used in quantitative thermodynamic studies of
surfactant micellization/demicellization. The reason for this could be ascribed to insufficient understanding
of temperature dependence of heat capacity of surfactant solutions (DSC data) in terms of thermodynamics
which leads to problems with design of the experiments and interpretation of the output signals. We
address these issues by: (i) careful design of DSC experiments performed with solutions of ionic and non-
ionic surfactants at various surfactant concentrations; (ii) individual and global mass-action model analysis
of the obtained DSC data. Our approach leads for all types of surfactants to reliable thermodynamic
parameters of micellization comparable with those obtained by isothermal titration calorimetry (ITC).
In our work we will present that DSC thermograms alone may contain sufficient information for
determination of thermodynamic parameters of micellization. To approach this goal, we have recently
suggested one possible way of analyzing DSC thermograms to obtain o
MG , o
MH , o
MS , o
,Mpc and n for a
series of non-ionic surfactants.[1] In the next step we will present the generalization of quantitative
thermodynamic analysis of DSC micellization-demicellization data for both ionic and non-ionic surfactants.
Therefore, we have studied thermally induced micellization/demicellization in four model systems: non-ionic
surfactant pentaethylene glycol monooctyl ether (C8E5) in water, cationic surfactant
dodecyltrimethylammonium chloride (DTAC) in 0.1 M NaCl solution and anionic surfactants sodium dodecyl
sulfate (SDS) and sodium lauroyl sarcosinate (SARC), both in water. The last belongs to the family of
amino acid-based surfactants, which are biodegradable and biocompatible and, to our knowledge, this is
the first DSC study of this type on this surfactant.
References:
[1] J. Lah, M. Bešter Rogač, , T.-M. Perger, G. Vesnaver, J. Phys. Chem. B 2006, 110, 23279-91.
Ion-lipid competition for hydration and interfacial sites at soft-matter interfaces
Epameinondas Leontidis,1,* Maria Christoforou,1 Chara Georgiou1 and Thomas Delclos1
1 Department of Chemistry, University of Cyprus, PO Box 2037, 1678 Nicosia, Cyprus
* e-mail: [email protected]
At charged surfaces “bound” ions reduce the repulsive electrostatic forces, while dissociated ions control
the osmotic pressure in colloidal systems. For systems charged through ionic adsorption on the other
hand, the adsorbed ions determine the charging boundary condition and colloidal interactions. Soft-matter
interfaces have considerable flexibility and compressibility, hence ionic adsorption at such interfaces may
generate new phenomena when (a) the ions compete with the lipid or polymeric components for water of
hydration, or (b) position themselves at the polar-nonpolar interface and modify its structure. We review
some recent advances on the understanding of specific ion effects from this perspective, and provide some
unpublished illustrative examples involving soft flexible interfaces. We propose an extension of the
chaotropic series to include disruptors of soft matter, which may act as cosurfactants or even as
hydrotropes. We also examine the effects of coordinating ligands on specific ion adsorption at soft
interfaces, using lanthanides as test cations, and discuss how such effects may be used to change the
affinities between ions and interfaces in controlled ways.
References:
[1] E. Leontidis, M. Christoforou, C. Georgiou, T. Delclos , Cur. Opin. Colloid Int. Sci. 2014, in press, DOI
10.1016/j.cocis.2014.02.003.
Perpendicular and « lateral » equations of state in layered systems of amphiphiles
Pierre Bauduin Thomas Zemb
Institute for separation chemistry of Marcoule (France)
For colloidal solutions containing any type of surfactant inducing the formation of locally flat interfaces, we show here that two equations of state are required to understand phase behaviour and stability: the perpendicular and the lateral equations of state. This applies to lamellar phases, locally lamellar connected or sponge phases, uni- and multilamellar vesicle phases formed by detergents, lipids, extractants and theta-shaped molecules in all solutions showing optical anisotropy.ICSM Marcoule (France)
For colloidal solutions containing any type of surfactant inducing the formation of locally flat interfaces, we show here that two equations of state are required to understand phase behaviour and stability: the perpendicular and the lateral equations of state. This applies to lamellar phases, locally lamellar connected or sponge phases, uni- and multilamellar vesicle phases formed by detergents, lipids, extractants and theta-shaped molecules in all solutions showing optical anisotropy.
Phase Behavior of Selected Artificial Lipids
Andreas Zumbuehl1,2*, Bodo Dobner3 and Gerald Brezesinski4
1 Department of Chemistry, University of Fribourg, 1700 Fribourg, Switzerland 2 Swiss National Centre of Competence in Research in Chemical Biology, Switzerland
3 Institute of Pharmacy, Martin Luther University of Halle-Wittenberg, 06120 Halle(Saale), Germany
4 Max Planck Institute of Colloids and Interfaces, Science Park Potsdam-Golm, 14476 Potsdam, Germany
* e-mail: [email protected]
The flexibility of biomembranes is based on the physical-chemical properties of their main components –
glycerophospholipids. The structure of these modular amphiphilic molecules can be modified through
organic synthesis making it possible to study specific physical-chemical effects in detail. In particular, the
roles of the hydrophobic tails of the phospholipids and their hydrophobic/hydrophilic interfacial backbone on
the phase behaviour are highlighted. The spatial orientation of the glycerol backbone changes from sn-1,2
to sn-1,3 phospholipids leading to an increase of the in-plane area of the molecule. The larger distance
between the hydrophobic tails can lead to membrane leaflet interdigitation. The introduction of methyl side
groups in the hydrophobic tails increases the fluidity of the bilayer. Depending on the position of the methyl
branches partial interdigitation is observed. In the case of bolaamphiphiles, methyl side groups have a
similar effect on the fluidity, but interdigitation cannot occur.
References:
[1] A. Zumbuehl, B. Dobner, G. Brezesinski, Current Opinion in Colloid & Interface Science 2014, in press.
Versatility of a GPI fragment in forming highly ordered polymorphs
G. Brezesinski, C. Stefaniu, I. Vilotijevic, D. Varón Silva, P. H. Seeberger
Max Planck Institute of Colloids and Interfaces,14476 Potsdam (Germany)
*e-mail: [email protected] Glycosylphosphatidylinositols (GPIs) are complex glycolipids that are commonly found in eukaryotic cells
as a posttranslational modification of proteins or as free GPIs displayed on the cell surface. Although their
main function is to anchor the attached protein (AP) to the cell membrane, the conserved nature of the
complex pseudo-pentasaccharide core of GPIs suggests biological roles beyond simple physical anchoring.
Here we present physical-chemical studies using a synthetic GPI-mimic 1 representing a minimal fragment
that might adequately emulate GPI behavior.[1] GPI fragment 1 forms a highly-ordered subgel phase
structure characterized by ordering of both head groups and alkyl chains in thin layers (Bragg peaks in the
mid-to-wide angle region). Such head group ordering was not observed in any of the previous studies on
double-chain phospholipids including phospholipids with head groups that can be engaged in hydrogen
bonding interactions. The observed structure is reminiscent of subgel phase structures [2] observed in lipid
dispersions after partial dehydration of the head groups during long incubation periods at low temperature.
While investigating the driving forces behind the formation of these ordered monolayers we have studied
polymorphism of 1 under different conditions employing surface-sensitive X-ray diffraction methods. Three
distinct polymorphs of 1 (I, II and III) were identified and characterized by GIXD. Polymorphs II (a
condensed monolayer structure) and III (highly ordered subgel phase) coexist on 8M urea solution allowing
for a detailed thermodynamic and kinetic analysis of the processes leading to the formation of these
polymorphs. They are enantiotropic and can be directly interconverted by changes in temperature or lateral
surface pressure. As a consequence, polymorph III nuclei of critical size (or larger) could be formed by
density fluctuations in a multi-component system and they could continue to exist for a period of time even
under conditions that normally would not allow for the nucleation of polymorph III. These findings may have
far-reaching biological implications. The processes described here could also lead to the formation of
patches of highly ordered structures in a disordered environment of a cell membrane suggesting that GPIs
may play a role in the formation of such domains.
Studies on mixed monolayers of 1 and POPC demonstrate that above a certain threshold concentration of
compound 1 phase-separation occurs due to the strong head group interactions. Below this threshold
concentration, compound 1 mixes with the liquid disordered POPC and induces order in a highly
cooperative way. Thus, the GPI fragment 1 tends to create ordered phases as it either forms a highly
crystalline structure, or induces liquid-ordered domains (rafts). This ability could have important implications
for the interactions of GPI-APs and GPIs in real cell membranes.
References:
[1] C. Stefaniu, I. Vilotijevic, M. Santer, D.V. Silva, G. Brezesinski, P.H. Seeberger, Angew. Chem. Int. Ed. 2012, 51,
12874.
[2] J. Katsaras, V.A. Raghunathan, E.J. Dufourc, J. Dufourcq, Biochemistry 1995, 34, 4684; D. Marsh, Chem. Phys.
Lipids 2012, 165, 59.
The dipole potential across a lipid layer: A modified Debye-Hückel model
Klemen Bohinc1*, Juan Jose Giner Casares2 and Sylvio May3
1 Faculty of Health Sciences, University of Ljubljana, Zdravstvena pot 5, 1000 Ljubljana, Slovenia
2 Departamento Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, 14014 Cordoba, Spain
3 Department of Physics, North Dakota State University, Fargo, ND 58105-5566, USA
* e-mail: [email protected] We consider a dipole potential of a mixed anionic-zwitterionic lipid membrane from experimental and
theoretical point of view. The potential difference across a lipid monolayer at the air-water interface for
different mixtures of anionic and zwitterionic lipids has been measured. In order to better understand the
experimental results we developed a theoretical model which pursues a minimalistic approach that aims at
retaining only the most relevant structural features. We employ a modified continuum Debye-Hückel model
which accounts for the dipolar nature of the zwitterionic head groups and explicitly models solvent
molecules as Langevin dipoles [1,2]. The ability of the headgroups to order the water molecules was also
taken into account. We show that our analytical model is able to describe both sign and magnitude of the
measured dipole potential.
References:
[1] K. Bohinc, A. Shrestha, S. May, Eur. Phys. J. E 2011, 34(10), 1-10.
[2]K. Bohinc, A. Shrestha, M. Brumen, S. May, Phys. Rev. E 2012, 85(3) 031130-1-031130-12.
Direct osmolyte-macromolecule interactions confer entropic stability to folded states
Nico F. A. van der Vegt1* and Francisco Rodriguez-Ropero1
1 Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
* e-mail: [email protected]
Protective osmolytes are chemical compounds that shift the protein folding/unfolding equilibrium towards
the folded state under osmotic stresses. The most widely considered protection mechanism assumes that
osmolytes are depleted from the protein first solvation shell leading to entropic stabilization of the folded
state. However, recent theoretical and experimental studies suggest that protective osmolytes may directly
interact with the macromolecule. As an exemplary and experimentally well-characterized system, we herein
discuss poly(N-isopropyl acrylamide) (PNiPAM) in water whose folding/unfolding equilibrium shifts towards
the folded state in the presence of urea. Based on Molecular Dynamics simulations of this specific system
we propose a new microscopic mechanism that explains how direct osmolyte-macromolecule interactions
confer stability to folded states. We show that urea molecules preferentially accumulate in the first solvation
shell of PNiPAM driven by attractive Van der Waals dispersion forces with the hydrophobic isopropyl
groups, leading to the formation of low entropy urea clouds. "Dissolution" of these clouds provides entropic
driving force for polymer collapse, balancing the unfavorable enthalpy at a lower coil-globule transition
temperature as compared to hydrophobic collapse in water. Electrostatic interactions and hydrogen
bonding play no role in the lowering of the coil-globule transition temperature. The proposed mechanism
provides a new angle on relations between the properties of protecting and denaturing osmolytes, salting-in
or salting-out effects and solvent non-idealities.
Competing forces in the interaction of polyelectrolytes with charged interfaces
Jordi Faraudo a, Alberto Martin-Molina b
a Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, E-08193 Bellaterra, Spain b Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Universidad de Granada,
Granada, Spain
* e-mail: [email protected]
In this review, we discuss the competition of non-DLVO forces in the adsorption of polyelectrolytes onto charged surfaces. We consider two particularly illustrative problems, namely the adsorption of polyelectrolytes onto similarly charged surfaces and the reversal of surface charge by adsorption of polyelectrolytes. Emphasis is made on how simulation results help to understand relevant experimental situations.
Competing mechanisms in polyelectrolyte multilayer formation and swelling: polycation/polyanion pairing
vs. polyelectrolyte/ion pairing
Dmitry Volodkin1, Regine v. Klitzing2
1 Fraunhofer BMT, Potsdam-Golm, Germany 2 Stranski-Laboratorium für Physikalische und Theoretische Chemie, TU Berlin, Germany
* e-mail: [email protected]
A complex interplay between different interactions determine the formation of polyelecrolyte multilayers
(PEM) prepared by the layer-by-layer method: Polyanion/polycation, ion/oppositely charged polyion and
ion/solvent interactions, the solubility of the polyanion/polycation complexes vs. the interactions between
the complexes with the surface. The talk addresses mainly the competition between the formation of
complexes of oppositely charged polyions on one hand and polyion/ion interactions on the other hand.
Large ions of high polarizability and a small hydration shell can easier interact with the oppositely charged
polyelectrolytes than small ions with a large hydration shell. The consequence is a higher extrinsic charge
compensation by counter ions and a lower density of complexation sites. This in turn leads to a more
mobile polymer matrix related to an exponential growth with endothermic formation of complexes.
In case of pronounced extrinsic charge compensation the PEM are denser with less voids in the dry state
due to stronger screening of the polyelectrolyte charges. This gives a higher flexibility of the polymer chains
and an easier adjustment of the chains to the environment. In contrast, these PEM swell stronger in water
than the ones built up in presence of small ions. Due to the lower density of complexation sites the “mesh
sizes" are larger and can uptake more water. PEM built-up in presence of larger are less stable. In case of
strong decrease in number of complexation sites due to strong polyion-ion interactions and/or high ionic
strength the PEM formation could become even impossible.
Open questions address still an explanation for the exponential growth and the “like seeks like” concept for
ions and polymer functional groups.
References:
Dmitry Volodkin, Regine v. Klitzing „Competing mechanisms in polyelectrolyte multilayer formation and swelling: polycation/polyanion pairing vs. polyelectrolyte/ion pairing“ COCIS, 19 (2014) 25–31.
Double-End-Tethered Polyelectrolyte Brush
Inna Dewald1*, Julia Gensel1, Johann Erath1, Eva Betthausen2, Axel H.E. Müller2,3, Andreas Fery1
1 University of Bayreuth, Physical Chemistry II, D-95440 Bayreuth 2 University of Bayreuth, Macromolecular Chemistry II, D-95440 Bayreuth
3 Johannes Gutenberg University Mainz, Institute of Organic Chemistry, D-55128 Mainz
* e-mail: [email protected]
Today, many objects of our everyday life consist of coated materials hinting at their growing importance in the modern era of technology. Especially the use of colloidal building blocks for thin film formation has several advantages from a material-science perspective, e.g. stimulus-response and multi-functionality on the single particle level, as well as the means to design functional surfaces by a simple but elegant approach of physisorption. Using the LbL approach for pH-responsive micelles leads to coatings with novel properties, internal hierarchy and collective stimulus response of the integrated nanostructures.
Here, we present a nanoporous multilayer system based on ABC triblock terpolymer micelles, which can reversibly switch their physico-chemical characteristics in reaction to external signals.[1] Furthermore, we investigate the macroscopic and reversible ionization-induced swelling transition, which entails large scale volumetric changes as a result of film microstructure. The key to the high swelling is the separation of the binding and responsive components within the LbL films, i.e. the responsive component – a double-end-tethered polyelectrolyte brush - is confined between the hydrophobic micellar core and the interpolyelectrolyte complex.[2]
References:
[1] Gensel J.1, Betthausen E.
2, Hasenöhrl C.
1, Trenkenschuh K.
1, Hund M.
1, Boulmedais F.
1, Schaaf P., Müller A. H.
E.2 and Fery A.
1, Surface immobilized block copolymer micelles with switchable accessibility of hydrophobic pockets,
Soft Matter, 2011, 7, 11144-11153.
[2] Gensel J.1, Dewald I.
1, Erath J.
1, Betthausen E.
2, Müller A. H. E.
2, Fery A.
1, Reversible swelling transitions in
stimuli-responsive layer-by-layer films containing block copolymer micelles, Chem. Sci., 2013, 4, 325-334.
Wood swelling with humidity: consequences of the force balance the Equation of State of Wood
Luca Bertinetti1* Peter Fratzl2 and Thomas Zemb3
1,2,3 Department of Biomaterials, Max-Planck-Institute of Colloids and Interfaces, Research Campus Golm,
14424 Potsdam, Germany 3 Institut de Chimie séparative de Marcoule UMR 5257 ,
F30207 Bagnols-sur-Cèze and Laboratoire Européen Aassocié “SONO”
* e-mail: [email protected] Wood consists of parallel, hollow, cylindrical cells. The so-called “wood material”, i.e. the materials the cell
walls are made of, is a complex, highly anisotropic and hierarchically organized nanocomposite. It is
characterized by stiff crystalline cellulose nanofibers parallel to each others embedded in a matrix of a
much softer, less anisotropic, macromolecules (hemicelluloses and lignin). The matrix is hygroscopic and
swells with increasing relative humidity, and, consequently, wood cells undergo significant dimensional
changes. Although this represents a major technological challenge and more of 80 sorption isotherms
models have been proposed to describe the wood swelling over more than 100 years, a model that takes
into account the structure and composition of the material, able to quantitatively give reason for the
thermodynamics of the phenomenon, still does not exist.1
Starting from literature structural and compositional data, we consider the wood material as a colloidal
system and we propose that water sorption isotherm in wood and osmotic pressure variation versus
distance between the cellulose crystals in wood cell wall can be represented by a unique and general
equation of state. The equation of state takes into account several opposite mechanisms: hydration force of
water around fibres of cellulose and partial entropy of mixing versus “contact points”, i.e. free energy
associated to hemicellulose (soft) cross-linking cellulose crystals. Because the wood is a nanocomposite
material in which the fibers act as an external constraint with respect to the swelling matrix, the mechanical
energy to deform the composite upon swelling was also taken into account.2
Besides giving insight on the fundamental mechanisms responsible for the wood swelling, this general
equation of state of wood can be applied to important technological aspects of the wood processing and
protection. In particular it can explain and qualitatively predict:
1 - Why anchoring of short chain fatty acids to wood cell macromolecules produces efficient protection (as
in the wood-protect process developed by Lapeyre CO tm).
2 - Why charging the cellulose crystal surface with salts containing hydrated tri-valent cations provides a
good method for dissolution of cellulose extraction.
3 - How increasing the Young’s modulus of the wood material by crosslinking the matrix polymers reduces
the swelling.
References:
[1] Engelund, E. T., Thygesen, L. G., Svensson, S. & Hill, C. A. S. Wood Sci Technol 2012, 47, 141–161.
[1] Bertinetti, L., Fischer, F. D. & Fratzl, P. Phys Rev Lett 2013, 111, 238001 (2013).
Dissolving and Coagulating Cellulose: Role of Hydrophobic Interactions
Lindman, B., Medronho, B. Miguel, M.
University of Coimbra, Department of Chemistry, Coimbra, Portugal and Center of Chemistry and Chemical Engineering, Lund University, Sweden
* e-mail: [email protected]
Cellulose is difficult to dissolve and the use of cellulose in formulations, including the formation of colloidal
particles and fibers is limited by solubility limitations. Cellulose is known to be insoluble in water and in
many organic solvents, but can be dissolved in a number of solvents of intermediate properties, like N-
methylmorpholine N-oxide (NMMO) and ionic liquids (ILs) which, apparently, are not clearly related. It can
also be dissolved in water at extreme pHs, in particular if a cosolute of intermediate polarity is added. The
insolubility in water is often referred to strong intermolecular hydrogen bonding between cellulose
molecules. Revisiting some fundamental polymer physicochemical aspects (i.e. intermolecular interactions)
a different picture is now revealed: cellulose is significantly amphiphilic and hydrophobic interactions are
important to understand its solubility pattern. We discuss the balance between hydrogen-bonding and
hydrophobic interactions as well as experimental support for the hydrophobic properties of cellulose.
Properties of fluorinated acrylic copolymer/ SiO2 hybrid superhydrophobic surfaces with tuneable wettability
Imre Dékány1,2* László Janovák1, Ágota Deák1, Mihály Sztakó1, Ádám Juhász3
1 Department of Physical Chemistry and Materials Sciences, University of Szeged, H-6720, Szeged, Rerrich
B. Square 1., Hungary 2 Supramolecular and Nanostructured Materials Research Group of Hungarian Academy of Sciences, H-
6720, Szeged, Dóm square 8., Hungary 3Nanocolltech Ltd H-6722 Szeged, Gogol u 9/B, Hungary
* e-mail: [email protected]
The interest in superhydrophobic surfaces has grown exponentially over recent decades [1, 2]. Inspired by
the amazing wettability of these natural species, many artificial superhydrophobic surfaces have been
fabricated [3]. Many methods have been developed to fabricate superhydrophobic surfaces. The several
techniques can be divided in top-down and bottom-up approaches. Top-down approaches include
lithography, template-based techniques, and plasma treatments of surface [4]. Examples of bottom-up
techniques are chemical deposition, layer-by-layer (LBL) deposition, and colloidal assemblies [5]. There are
also methods based on the combination of both top-down and bottom-up techniques such as casting of
polymer solution, phase separation, and electrospinning [3].
In the present work superhydrophobic surfaces were produced using hydrophobic or hydrophilic SiO2
nanoparticles (d=~15 nm) and fluorinated acrylic copolymer [poly(methyl-methacrylate-co-perfluorohexyl-
methacrylate)] by spray coating techniques. The initial hydrophilic SiO2 nanoparticles were modified with
fluorinated and non-fluorinated molecules for lower surface energy. Particle to binder ratio was optimized
for fluoroacrylic/SiO2 nanoparticle formulations to obtain contact angles of interest. The wetting properties
of the prepared thin films were investigated by contact angle measurements. According to the results the
measured water contact angle values (θadv) were varied between 106° and 163° depending on the SiO2
nanoparticles content. The calculated surface energy of solids (γsv, determined by Zisman-method) was
lower than 26.4 mJ/m2. The structural observation of thin films was carried out by SEM. Surface topography
and peak-to-valley roughness (Ra=Zmax-Zmin, where Zmax and Zmin are the highest peak and the lowest
valley, respectively) of as-prepared coatings was examined by AFM in the tapping mode. The structure of
the prepared hydrophobic particles and thin layers were also studied by infrared spectroscopy. Using a
simple template method, unsaturated polyester resin was chose to replicate the structure of the prepared
superhydrophobic thin layers. This template method needs neither expensive instruments nor complicated
chemical treatments.
References:
[1] E. Celia, T. Darmanin, E. Taffin de Givenchy, S. Amigoni, F. Guittard, Journal of Colloid and Interface Science
2013, 402, 1–18
[2] K. Liu, X. Yaob, L. Jiang, Chemical Society Reviews 2010, 39, 3240-3255
[3] A. Steele, I. Bayer, E. Loth, Nano Letters 2009, 9, 501–505.
[4] E. Lepore, C. Chappoz, D. C. Monetta, N. Pugno, Composite Structures 2013, 100, 609–616.
[5] D. Ebert, B. Bhushan, Langmuir 2012, 28, 11391−11399
Description of protein adsorption in terms of colloidal interactions
Maciej Szaleniec1, Pavel Dyshlovenko2, Lilianna Szyk-Warszynska1, Piotr Warszynski1*
1 J. Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Science, ul. Niezapominajek 8, 30-239 Kraków, Poland
2 Ulyanovsk State Technical University, Severny Venets Street 32, 432027 Ulyanovsk, Russia
* e-mail: [email protected]
Protein adsorption at solid-liquid interfaces is an important issue in many fields such as: bio- and
hemocompatible materials, diagnostic kits or enzymatic activity in mineral soils. The theoretical description
of the protein adsorption phenomena is very complicated due to combination of many types of interactions
involved as: electrostatic, dispersive, hydrophobic/hydrophilic, specific ion effects. Just considering only the
electrostatic interactions with solid surface we need to take into account that the surface charge of proteins
is pH dependent and non-uniformly distributed. The concept of non-uniform charge distribution is usually
used to explain anomalous adsorption of proteins at the charged surfaces carrying the surface charge of
the same sign as the mean charge of protein. For example human serum albumin (HAS), which above pH
5 has net negative charge and can be deposited at mica surface [1], whereas casein can be deposited can
be deposited on silica surface in the broad pH value regardless that it has isoelectric point around pH 5.
We used molecular modeling calculation to determine the distribution of the surface charge at the selected
proteins (α-chymotrypsin, α- and β-casein, HSA). The modeling was conducted in Accelrys Discovery
Studio 3.5 package using CHARMm force field. The enzyme’s pI was calculated with ‘Calculate Protein
Ionization and Residue pK’ protocol and the protein net charge was estimated for pH conditions at, below,
and above pI point. The obtained partial charges were mapped to Connoly surface of each proteins. The
charge distribution on the surface was examined with custom-made protocol in Accelrys Material Studio.
We compared the dependencies of the net charge of proteins on pH obtained from the calculation with
ones measured experimentally by the microelectrophoresis. Then, we evaluated the electrostatic
interactions between proteins having nonuniform distribution of surface charge with uniformly charged,
planar interface. The interaction force exerted on the particle were calculated by solving numerically three
dimensional nonlinear Poisson-Boltzmann equation. The interaction energy was calculated by integration of
the force distance relationship. These theoretical predictions were used for the interpretation of
experimental data [1-4] for the adsorption and desorption kinetics of proteins at mica surface.
References:
[1] M. Dabkowska, Z. Adamczyk, Langmuir. 2012 28, 15663−15673.
[2] M. Wasilewska, Z. Adamczyk, Langmuir. 2011 27, 686-96.
[3] V.Z. Spassov; L. Yan, Protein Science 2008, 17, 1955-1970.
[4] E.N. Vasina, P. Dejardin, Langmuir, 2004, 20, 8699-8706
Bridging interactions of proteins with silica nanoparticles
Jens Meissner, Bhuvnesh Bharti and Gerhard H. Findenegg Institut für Chemie, Stranski Laboratorium, TC 7, Technische Universität Berlin, Straße des 17. Juni 124, D-
10623 Berlin, Germany ‡ Present address: Department of Chemical and Biomolecular Engineering, North Carolina State University,
Raleigh, NC 27695, USA
* e-mail: [email protected] The interaction of proteins with nanoscale materials plays a key role in modern biotechnology and in the
biomedical field. Charge-driven bridging of nanoparticles by macromolecules represents a promising route
for engineering functional structures, but the strong electrostatic interactions involved when using
conventional polyelectrolytes impart irreversible complexation and ill-defined structures. Here we study the
combined influence of pH and electrolyte concentration on the bridging aggregation of silica nanoparticles
with lysozyme.i We find that protein binding to the silica particles is determined by pH irrespective of the
ionic strength. The hetero-aggregate structures formed by the silica particles with the protein were studied
by small-angle X-ray scattering and the structure factor data were analyzed on the basis of a short-range
square-well attractive pair potential. It is found that the electrolyte concentration determines the stickiness
of particles near pH 5, where the weakly charged silica particles are bridged by strongly charged protein.
An even stronger influence of the electrolyte is found near the isoelectric point of the protein (pI 11) which
is attributed to the shielding of repulsive interactions between the highly charged silica particles, and to
hydrophobic interactions between the bridging protein molecules.
Proteins in Colloidal Systems: Boon or Bane?
Inna Dewald, Olga Isakin, Andreas Fery, Munish Chanana*
University of Bayreuth, Physical Chemistry II, D-95440 Bayreuth
* e-mail: [email protected]
Nanoparticles (NPs) can be easily synthesized in large quantities and with high dimensional precision via
wet chemical synthesis procedures, and depending on their physical, chemical and physicochemical
properties, these systems find applications in diverse fields of biomedicine, imaging, sensors, catalysis etc.
However, it is the coating material that ultimately limits the application of such particles, due to issues such
as colloidal stability, wettability, and toxicity, which strongly depend on the properties of the coating
material. Particularly in complex media such as bio-fluids or bio-relevant media, proteins tend to adsorb
instantly on nanoparticles which interact or even compete with the original stabilizing coating material,
changing the physicochemical properties in an ambiguous manner. In this work, we present nanoparticles,
which are readily coated with proteins and therefore exhibit a) extremely high colloidal stability, even in
complex biological media; b) remarkable physicochemical and wettability properties and keen sensitivity
towards pH, temperature and heavy metals, with a pronounced optical response, which can be monitored
even by naked eye. Moreover, such NPs are also highly biocompatible. Hence, protein coatings present
multiple advantages in comparison to common coating materials based on synthetic polymers and
polyelectrolytes.[1-3]
References:
1. Chanana, M., M.A. Correa-Duarte, and L.M. Liz-Marzán, Insulin-Coated Gold Nanoparticles: A Plasmonic Device
for Studying Metal–Protein Interactions. Small, 2011. 7(18): p. 2650-2660.
2. Chanana, M., et al., Physicochemical Properties of Protein-Coated Gold Nanoparticles in Biological Fluids and Cells
before and after Proteolytic Digestion. Angewandte Chemie International Edition, 2013. 52(15): p. 4179-4183.
3. Strozyk, M.S., et al., Protein/Polymer-Based Dual-Responsive Gold Nanoparticles with pH-Dependent Thermal
Sensitivity. Advanced Functional Materials, 2012. 22(7): p. 1436–1444.
Adsorption of proteins at the solution/air interface influenced by added non-ionic surfactants at very low concentration
M. Lotfi1,2, A. Javadi1,3, V. Ulaganathan1, C. Gehin-Delval4, D. Gunez4, M.E. Leser4, V.B. Fainerman5
and R. Miller1
1 MPI Colloids and Interfaces, Potsdam, Germany 2 Sharif University of Technology, Tehran, Iran
3 Chemical Engineering Department, University of Tehran, Tehran, Iran 4 Nestlé Research Center, CH-1000 Lausanne 26, Switzerland
5 Medical University Donetsk, Donetsk, Ukraine
* e-mail: [email protected] The adsorption of proteins at liquid interfaces happens at rather low solution bulk concentrations due to
their very high surface activity. In contrast to classical surfactants like SDS, DoTAB or octanol, which start
to decrease the surface tension at at a bulk concentration of about 10-4mol/l and reach a minimum value at
about two orders of magnitude higher concentration, proteins adsorb at much lower molar concentrations.
Most popular and frequently studied proteins are the whey proteins ß-lactoglobulin (BLG) and ß-casein
(BCS), or bovine serum albumin (BSA), the aqueous solutions of which reach a surface tension of about
50 mN/m at bulk concentrations of 10-6 mol/l. Due to these low bulk concentrations, the adsorption process
is consequently very slow and can last many hours or even days. One of the peculiarities is the so-called
induction time, a period of time after creation of the surface at which the adsorption of protein molecules
happens but no change in surface tension is observed. This induction time decreases with increasing
protein bulk concentration.
Due to the addition of extremely small amounts of non-ionic surfactants a BLG solution, for example 10-10
mol/l C12DMPO, more than 5 orders of magnitude lower than the corresponding CMC (3×10-4 mol/l), the
induction time and the entire adsorption kinetics is changed, as it is shown in the figures below [1].
References:
[1] M. Lotfi, A. Javadi, V. Ulaganathan, C. Gehin-Delval, D. Gunez, M.E. Leser, V.B. Fainerman and R. Miller,
Adsorption of proteins at the solution/air interface influenced by added non-ionic surfactants at very low concentration,
to be submitted to J. Phys. Chem. B
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63
68
73
1 10 100 1000
Su
rfa
ce
te
nsio
n
[mN
/m]
Time [s]
C12DMPO Solution/Air Interface
e-7 MC12…
Shear Rheology of Mixed Adsorption Layers with Hydrophobin vs Their Structure Studied by Surface Force Measurements
Peter A. Kralchevsky,1 Gergana M. Radulova,1 Krassimir D. Danov,1 Elka S. Basheva,1
Simeon D. Stoyanov,2,3 and Eddie G. Pelan2
1 Dept. Chem. Eng., Fac. Chemistry & Pharmacy, Sofia University, Sofia 1164, Bulgaria 2 Unilever Research & Development Vlaardingen, 3133AT Vlaardingen, Netherlands
3 Lab. of Phys. Chem. & Colloid Sci., Wageningen Univ., 6703 HB Wageningen, Netherlands
* e-mail: [email protected] The hydrophobins are proteins that form the most rigid adsorption layers on the air-water and oil-water
interfaces in comparison with the other amphiphilic proteins. A strong short-range attraction (hydrophobic
surface force) was detected between two HFBII hydrophobin adsorption layers across water [1]. Here, we
investigate single adsorption layers and foam films from mixed solutions of HFBII with the milk protein -
lactoglobulin (BLG) and the egg protein ovalbumin (OVA), as well as with the nonionic surfactant Tween
20. The results are compared with those for adsorption layers from HFBII alone and from HFBII + -casein.
The rheology measurements were carried out by a rotational rheometer with adsorption layers at the air-
water interface. The data for the interfacial shear stress comply with a viscoelastic thixotropic rheological
model [2]. The addition of BLG and OVA increases the shear elasticity and viscosity of the HFBII
adsorption layers. In contrast, the addition of the disordered protein -casein and of Tween 20 significantly
decreases the surface rigidity. To understand how the differences between the rheological behaviors of the
investigated systems are related to the structure of the respective mixed protein layers, we carried out
experiments with thin foam films. The results imply that the hydrophobin and BLG (or OVA) form two
separate adherent layers at the interface. Conversely, the -casein and Tween 20 form a mixed layer with
the HFBII and their presence disturbs the integrity of the hydrophobin elastic membrane. The obtained
results indicate that it is possible to replace up to 90–95 % of the hydrophobin in the solution with a globular
milk or egg protein without any essential decrease of the surface rigidity, and reveal the possible reasons
for this effect.
References:
[1] E.S. Basheva, P.A. Kralchevsky, K.D. Danov, S.D. Stoyanov, T.B.J. Blijdenstein, E.G. Pelan, A. Lips, Langmuir
2011, 27, 4481–4488.
[2] K.D. Danov, G.M. Radulova, P.A. Kralchevsky, K. Golemanov, S.D. Stoyanov. Faraday Discus. 2012, 158, 195–
221.
Lipid Transfer in O/W Emulsions, Influence of Diffusivity and Type of Stabilizer
Otto Glatter, Amin Sadeghpour, Franz Pirolt, Guillermo Ramón Iglesias
Karl-Franzens-University Graz, Austria
* e-mail: [email protected] Transfer of lipids between nanostructured droplets in surfactant stabilized and Pickering O/W emulsions
has been studied by time-resolved small angle X-ray scattering (SAXS). The special features of self-
assembled liquid-crystalline phases have been applied to examine the kinetics of internal phase
reorganization imposed by lipid release and uptake by the droplets. The findings reveal faster transfer
kinetics in Pickering emulsions [1] than in emulsions stabilized with Pluronic F127 even though the opposite
effect was expected! This finding is not yet fully understood and could possibly be explained by the differing
interfacial coverage of the emulsion droplets.
It is shown that the transfer kinetics can be accelerated by adding free surfactant to the dispersions, and
that this acceleration becomes more dominant when free micelles are formed.
The effect of immobilization of the droplets has been studied by incorporating them into the appropriate
hydrogel network. In such conditions, and at high enough concentrations of the hydrogel where non-ergodic
systems are obtained, the droplets are arrested and the transfer slows down significantly [2,3].
References:
[1] Sadeghpour, A.; Pirolt, F.; Glatter, O., Langmuir 2013, 29, 6004-12
[2] Iglesias, G. R.; Pirolt, F.; Sadeghpour, A.; Glatter, O., Langmuir 2013, 29, 15496-15502
[3] Sadeghpour, A.; Pirolt, F.; Iglesias, G. R.; Glatter, O., Langmuir 2014, under consideration
Engineering Electrified Interfaces
Marta Dobrowolska1,2 and Ger Koper1*
1 Delft University of Technology, the Netherlands 2 presently at INCOTEC, the Netherlands
* e-mail: [email protected]
Despite the fact that already in 1861 it was known that air-water interfaces are charge carrying[1], up till
today no satisfactory explanation has been put forward. Also the oil-water interface is known to be charged
and at present there is an ongoing debate on the origin of this phenomenon where experimental results as
well as numerical simulations are disputed, see [2] and references therein. Nevertheless, the simple
experimental fact persists that interfaces between hydrophobic material and water are charged. The
simplest and yet the most successful phenomenological model[3] describes the charging of the interface
using the assumption of single site dissociation[4]. It predicts that beyond pH 4, there is an excess of
hydroxyl ions at the interface which is accordance with experimental facts on the pH-stat homogenization of
oil-in-water emulsions[5].
Recently, we have performed a set of projects that all utilize the presence of charge at the interface
between hydrophobic material and water:
• Surfactant-free emulsification[6], where we have created hexadecane-in-water emulsions by means of
super-saturation and studied the long-term stability. Particularly striking was the phenomenon that the
emulsion droplets exhibit significant short and long time size and zeta-potential fluctuations that could be
due to the much more dynamic nature of the surface charge excess as compared to the canonical case of
surface charge due to dissociation or strict adsorption.
• Surfactant-free mini-emulsification[7] was subsequently used to oppose the effect of Ostwald ripening by
adding a hydrophobe to the emulsified oil. This additional degree of freedom did not lead to a reduction of
the fluctuations.
• Surfactant-free emulsion polymerization[8] involving a non-ionic, and hence uncharged initiator was
successfully used to synthesize latex particles. The width of the size distribution was found to vary strongly
with experimental conditions, notably the ionic strength and to a much lesser extent pH. The phenomenon
is explained by a critical ionic strength dependence of the aggregation of the just nucleated primary
particles into larger secondary particles, the so-called “coagulative nucleation” step.
We shall discuss the results of these projects in detail as we believe they shed new light on a long-standing
fundamental problem in colloid and interface science.
References: [1] Quincke, G. Poggendorf's Ann. Phys. Chem 1861, 113, 513. [2] Beattie, J. K.; Gray-Weale, A. Angew. Chem.-Int. Edit. 2012, 51, 12941. [3] Marinova, K. G. et al, Langmuir 1996, 12, 2045. [4] Healy, T. W.; Fuerstenau, D. W. J. Colloid Interface Sci. 2007, 309, 183 [5] Beattie, J. K.; Djerdjev, A. M. Angew. Chem.-Int. Edit. 2004, 43, 3568 [6] Dobrowolska, M.E., Thesis TU Delft, chapter 5. [7] Dobrowolska, M.E., Thesis TU Delft, chapter 6. [8] Dobrowolska, M.E. and Koper, G.J.M., Soft Matter 2014, 10, 1151-4.
Predicting Forces between Colloidal Particles in the Presence of Multivalent Ions
F.J. Montes Ruiz-Cabello*, Gregor Trefalt, Plinio Maroni and Michal Borkovec
Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, Quai Ernest-
Ansermet 30, 1205 Geneva, Switzerland
*Email: [email protected] Direct force measurements involving oppositely charged micron-sized particles were carried out across
aqueous solutions of different multivalent ions with the atomic force microscope (AFM). The measurements
could be interpreted quantitatively with Poisson-Boltzmann (PB) theory. Thereby, the surface potentials and
regulation properties of the particles are extracted from the forces between the same types of particles.
This information is then used to predict force profiles involving different types of particles without any
adjustable parameters. These predictions turn out to be very accurate, which demonstrates that the mean-
field PB theory is surprisingly reliable down to distances of about 5 nm. An example of this analysis is
shown in figure 1 below, which also indicates the importance of charge regulation. Similar findings were
made for a wide range of different multivalent ions. The possibility to accurately predict force profiles in the
presence of multivalent ions with PB theory is at odd with various reports in the literature, which state that
this theory should fail in such situation due to neglect of ion correlations [1,2]. We suspect that ion
correlations only induce deviations at smaller distances.
Figure 1. Force profiles involving amidine latex (AL) and the sulfate latex (SL) measured in 0.1 mM
K4Fe(CN)6 solutions of are compared with PB theory. In symmetric systems, involving (b) SL-SL and (c)
AL-AL particle pairs, the theory is used to determine the surface potentials and regulation parameters p
indicated in the figures. (c) PB theory is validated by comparing its prediction with force measurements in
the asymmetric AL-SL system. Charge regulation effects are essential, since constant charge (CC) and
constant potential (CP) conditions differ widely.
References:
[1] R. Kjellander, T. Akesson, B. Jonsson, and S. Marcelja, J. Chem. Phys. 97, 1424 (1992).
[2] M. M. Hatlo and L. Lue, Soft Matter 5, 125 (2009).
Ion Mobility and Clustering of Sodium Hydroxybenzoates in Aqueous Solutions: A Molecular Dynamics Simulation Study
J. Gujt1,2*, Č. Podlipnik1, M. Bešter-Rogač1, and E. Spohr2
1 Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia
2 Lehrstuhl für Theoretische Chemie, Fachbereich Chemie, Universität Duisburg-Essen,
D-45141 Essen, Germany
* e-mail: [email protected]
The relative position of the hydroxylic and the carboxylic group in the hydroxybenzoate (HB) anion has a
great impact on transport properties of this species [1] and influences crucially the self-organisation of
cationic surfactants [2-5]. The transition from rod to spherical micelles of CTAC in the presence of o-HB has
already been studied on the molecular level by means of molecular dynamics simulations (MDS) [6].
However, no studies has been done so far, that would deal with the influence of other two HB isomers on
the micellisation of cationic surfactants on the molecular level.
Before we attempt to conduct such a study, it is pertinent to get some insight into the behaviour of pure
NaHB salts in aqueous solutions. We were particularly interested in the interaction of different HB isomers
with water molecules and with another HB anion. In this contribution first the results of MDS of all three
HB isomers in two different water models at low and higher concentration will be presented. From the
resulting trajectories the self-diffusion coefficient of each isomer was calculated. They are ranked in the
order o-HB > m-HB > p-HB at both concentration, which agrees very well with the experiment [1,2].
Next, the structural analysis reveales that at lower concentration, where the tendency for the dimerisation
or the formation of clusters is low, hydrogen bonding with water determines the mobility of HB anion. o-HB
forms the least hydrogen bonds and is therefore the most mobile, whereas p-HB, which forms the most
hydrogen bonds with water, is the least mobile isomer. At the higher concentration of the salt the trend of
mobilities is still the same, but the trend in hydration differs. Ortho isomer again forms the lowest number of
hydrogen bonds with water, but other two are approximately equally well hydrated. The difference between
these two arises from differences in the formation of clusters. Ortho isomer predominantly forms dimers
(about 2/3 of molecular ions are in dimers) with two hydrogen bonds between HB anions per dimer. Meta
isomer forms cluster of sizes up to 8 and about one half of unimers are present as free ions. p-HB forms
clusters of size up to 17, which can be either rings or chains, with less than 25 % of HB anions as free
ions.
Finally, we will propose the most probable structures of HB clusters in aqueous solutions.
References: [1] M. Bešter-Rogač, J. Chem. Eng. Data 2011, 56, 4965-4971. [2] B. Šarac, J. Cerkovnik, B. Ancian, G. Mériguet, G. M. Roger, S. Durand-Vidal, M. Bešter-Rogač, Colloid Polym. Sci. 2011, 289, 1597-1607. [3] B. Šarac, G. Mériguet, B. Ancian, M. Bešter-Rogač, Langmuir 2013, 29, 4460-4469. [4] K. Bijma, M. J. Blandamer, J. B. F. N. Engberts, Langmuir 1998, 14, 79-83. [5] K. Bijma, E. Rank, J. B. F. N. Engberts, J. Colloid Interface Sci. 1998, 205, 245-256. [6] Z. Wang, R. G. Larson, J. Phys. Chem. B 2009, 113, 13697-13710.
Growth and branching of micelles: competing interactions turn out synergistic
Martin In*
CNRS, Laboratoire Charles Coulomb UMR 5221, 34095 Montpellier, France
* e-mail: [email protected]
Wormlike micelles consist of long cylindrical supramolecular self-assemblies of amphiphilic
molecules. Beside the main cylindrical curvature, wormlike micelle present heterogeneities in
the curvature since they are necessarily terminated by spherical end cap and can present
junctions that are locally flat [1]. The concentration of these defects of curvature which results
from a balance of enthalpic and entropic contributions [2] has been determined by SANS on
model systems provided by Gemini surfactants [3].
Due to long range electrostatic repulsions, small angle neutron scattering patterns of Gemini
wormlike micelles are characterized by a correlation peak at finite wave vector q*. The
volume fraction dependence of q* crosses over continuously through different scaling laws
analogous to the ones observed in lyotropic mesophases: q* 1/D, with D=3 for spherical
micelles, D=2 for cylindrical and D=1 for sheets. The crosses over do not correspond to any
phase transitions but are due to the morphological transitions in the micellar phase. As a
consequence, intermediate values of q* lying in between the typical swelling laws are
observed and allow to characterize the growth and branching.
In the dilute regime, q* is determined by the number density of micelles and is analyzed in
terms of aggregation number N of the micelles. Temperature dependence of N yields the
endcap energy. In the semi-dilute regime, a simple model is proposed to interpreted q*
values in terms of branching ratio.
Characterizing growth and branching of micelles through the variation of the characteristic
distance of the system points out the boosting effect of long range repulsions in
condensation phenomena that rely on attractions to proceed.
References: [1] Kralchevsky, P.A., Danov, K.D., Anachkov, S.E., Georgieva, G.S., Ananthapadmanabhan, K.P., COCIS (2013) 18, 524-531. [2] Kocherbitov V., COCIS (2013) 18, 510-516. [3] In M., Bendjeriou B., Noirez L., Grillo I., Langmuir 26(13), 10411-10414 (2010).
Ionosilicas: Periodic Mesoporous Organosilicas from Ionic Precursors
Peter Hesemann1* and Thy Phuong Nguyen1, Samir El Hankari1 and Philippe Moisy2
1 Institut Charles Gerhardt de Montpellier, Place E. Bataillon, F-34095 Montpellier cedex 05 2 CEA Marcoule (CEA/DEN/DRCP)
Ionosilicas are defined as silica based materials containing covalently tethered ionic groups. These
materials, situated at the interface of silica hybrid materials and ionic liquids, have large potential in
catalysis, molecular recognition and separation. This talk will summarize our ongoing efforts in different
areas related to the synthesis and applications of ionosilicas. In a first part, we will focus on different
aspects of the formation of nanostructured ionosilica phases displaying defined architectures on a
mesoscopic level. Ionosilicas are obtained via template directed hydrolysis-polycondensation reactions
involving ionic trialkoxysilylated precursors. Nanostructured phases can be obtained thank to specific
interactions of these ionic precursors with complementary surfactants. We will show that the formation of
structured phases can only be achieved from suitable surfactant-precursor ion pairs. This approach is
particularly appealing as both the nature of the organo-ionic part of the precursor and the chemical
constitution of the surfactant can be modulated. The second part is devoted to applications of ionosilicas in
catalysis and separation. Ionosilicas show interesting catalytic properties in various organocatalytic
reactions. In several cases, synergistic effects between silica support and the tethered ionic substructure
allow increasing significantly the catalytic activity compared to pure ionic liquids. Finally, ionosilicas appear
as efficient ion exchange materials displaying Hofmeister selectivity.
References:
[1] T.P. Nguyen, P. Hesemann, T.M.L. Tran, J.J.E. Moreau J. Mater. Chem. 2010, 20, 3910
[2] T.P. Nguyen, P. Hesemann, J.J.E. Moreau Microporous and Mesoporous Materials, 2011, 142(1), 292
[3] S. El Hankari, B. Motos-Pérez, P. Hesemann*, A. Bouhaouss, J.J.E. Moreau. Mater. Chem. 2011, 21, 6948
[4]. El Hankari, B. Motos-Pérez, P. Hesemann*, A. Bouhaouss, J. J.E. Moreau Chem. Commun. 2011, 47, 6704
[5] S. El Hankari, P. Hesemann Eur. J. Inorg. Chem. 2012, 5288
[6] S. El Hankari, A. Bouhaouss, P. Hesemann Microporous and Mesoporous Materials, 2013, 180, 196
Participants Dr. Luca Bertinetti Max-Planck-Institut for Colloids and Interfaces Am Mühlenberg 1 14424 Potsdam Golm Germany Phone: +49 331 567 - 9411 Email: [email protected] Dr. Klemen Bohinc University of Ljubljana Faculty of Health Sciences Zdravstvena 5 1000 Ljubljana Slovenia Phone: +386 1 3001170 Email: [email protected] Rym Boubekri Laboratoire Charles Coulomb Place Eugène Bataillon 12345 Montpellier France Phone: +33 467 143525 Email: [email protected] Prof. Dr. Gerald Brezesinski Max-Planck-Institute for Colloids and Interfaces Am Mühlenberg 1 14424 Potsdam Golm Germany Phone: +49 331 567 - 9234 Philipp Buchold Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Phone: +49 30 314 – 22750 Email: [email protected] Dr. Cyrille Claudet Laboratoire Charles Coulomb, UMR5221 CNRS – Université Montpellier 2 Place Eugène Bataillon 34095 Montpellier France Phone: +33 467 143860 Email: [email protected]
Dr. Munish Chanana Universität Bayreuth Physikalische Chemie II Universitätsstraße 30 95447 Bayreuth Germany Phone: +49 921 55 - 3915 Email: [email protected] Prof. Dr. Imre Dékány University of Szeged Department of Colloid Chemistry Aradi v.t. 1. 6720 Szeged Hungary Phone: +36 62 544209 Email: [email protected] Inna Dewald Universität Bayreuth Physikalische Chemie II Universitätsstraße 30 95447 Bayreuth Germany Phone: +49 921 55 - 2755 Email: [email protected] Dr. Anne-Laure Fameau INRA Rue de la Géraudière 44300 Nantes France Phone: +33 673 212143 Email: [email protected] Dr. Jordi Faraudo Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC) Campus UAB s/n 08193 Bellaterra Spain Phone: +34 931 888786 Email: [email protected] Prof. Otto Glatter Graz University of Technology Department of Inorganic Chemistry Tel: +43 316 873 32146 (32101 Secr.) Stremayrgasse 9/V Mobile: +43 664 7349 9150 8010 Graz Austria Phone: +43 664 73499150 Email: [email protected] Jure Gujt University of Ljubljana Faculty of Chemistry and Chemical Technology Aškerčeva 5 1000 Ljubljana Slovenia Phone: +49 176 97591937 Email: [email protected]
Dr. Thomas Gutberlet Helmholtz Zentrum Berlin Hahn-Meitner-Platz 1 14109 Berlin Germany Phone: +49 30 8062 - 42778 Email: [email protected] Prof. Daniel Harries The Hebrew University Institute of Chemistry Givat Ram, Safra Campus 91904 Jerusalem Israel Phone: +97 2 543052407 Email: [email protected] Dr. Peter Hesemann Université de Montpellier 2, CC1701 Institut Charles Gerhardt Place Eugène Bataillon 34095 Montpellier France Phone: +33 662 522266 Email: [email protected] Dr. Martin In Centre national de la Recherche Scientifique Laboratoire Charles Coulomb Place Eugène Bataillon 34095 Montpellier France Phone: +33 467 143593 Email: [email protected] Prof. Dr. Regine von Klitzing Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Telefon: +49 30 314 - 23476 Email: [email protected] Dr. Vitaly Kocherbitov Malmö University Faculty of Health and Society, Biomedical Sciences Jan Waldenströms Gata 25 20506, Malmö Sweden Phone: +46 40 6657946 Email: [email protected]
Dr. Ger Koper TU Delft Department of Chemical Engineering Julianalaan 124 2628 Delft The Netherlands Phone: +31 15 278 - 8218 Email: [email protected] Prof. Peter A. Kralchevsky Sofia University Faculty of Chemistry and Pharmacy Department of Chemical Engineering James Bourchier Blvd., No. 1 1164 Sofia Bulgaria Phone: +359 2 8161 - 262 Email: [email protected] Prof. Epameinondas Leontidis University of Cyprus Kallipoleos 75 1678 Nicosia Cyprus Phone: +357 2 2892767 Email: [email protected] Prof. Björn Lindmann University of Lund Physical Chemistry P.O. Box 124 221 00 Lund Sweden Phone: +46 46 222 - 8160 Email: [email protected] Dr. Alexandre Mantion Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Telefon: +49 30 314 – 29887 Email: [email protected] Jens Meißner Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Telefon: +49 30 314 - 24938 Email: [email protected]
Sarah Metzke Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Telefon: +49 30 314 – 25270 Email: [email protected] Prof. Maria Miguel University of Coimbra Chemistry Department R. Larga, Polo I 3004-535 Coimbra Portugal Phone: +351 239 854485 [email protected] Dr. Reinhard Miller Max-Planck-Institut for Colloids and Interfaces 14424 Golm/Potsdam Germany Phone: +49 331 567 - 9252 Email: [email protected] Prof. Dr. Roland Netz Freie Universität Berlin Theoretische Biophysik und Physik weicher Materie Arnimallee 14 14195 Berlin Germany Phone: +49 30 838 - 55737 Email: [email protected] Sven Riemer Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Phone: +49 30 314 - 24790 Email: [email protected] Dr. Muriel Rovira Esteva Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Phone: +49 30 314 - 23469 Email: [email protected]
Dr. Francisco Javier Montes Ruiz-Cabello University of Geneva Quai Ernest-Ansermet 30 1205 Geneva Switzerland Phone: +41 22 3796055 Email: [email protected] Dr. Bojan Šarac University of Ljubljana Faculty of Chemistry and Chemical Technology Aškerčeva 5 1000 Ljubljana Slovenia Phone: +386 1 2419418 Email: [email protected] Salomé Vargas Ruiz Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Phone: +49 30 314 – 24323 Email: salomé[email protected] Prof. Dr. Nico van der Vegt Technische Universität Darmstadt Center of Smart Interfaces Alarich-Weiß-Strasse 10 64287 Darmstadt Germany Phone: +49 6151 16 - 4356 Email: [email protected] Kathrin Voigtländer Technische Universität Berlin Institut für Chemie Stranski-Laboratorium für Physikalische und Theoretische Chemie Sekretariat TC 9 Straße des 17. Juni 124 10623 Berlin Germany Phone: +49 30 314 - 24790 Email: [email protected] Prof. Piotr Warszynski Jerzy Haber Institute of Catalysis and Surface Chemistry PAS Niezapominajek 8 30-239 Kraków Poland Phone: +48 12 6395 - 123 Email: [email protected]
Thomas Zemb Marcoule Institut for Seperative Chemistry ICSM UMR 5257 – CEA / CNRS / UM2 / ENSCM Site de Marcoule, Bâtiment 426 BP 17171 F-30207 Bagnols sur Cèze France Tel: +33 4 66339279 Email: [email protected] Dr. Andreas Zumbuehl University of Fribourg Department of Chemistry Chemin du Musée 9 1700 Fribourg Switzerland Phone: +41 26 300 - 8794 Email: [email protected]
