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How to Teach Polymers New Tricks(exploiting nanoscale effects)
Christoph Weder
Micronarc Industrial ForumMicronarc Industrial ForumFribourg, 10.11. 2010
Interdisciplinary center of competence in fundamental d li d ft d t i l i
Office of theProvost
and applied soft nano- and materials science
Faculty of Science Adolphe
Merkle Foundation
Biology
Chemistry Geosciences
InformaticsMathematics
Physics Institute Council
ScientificAdvisory
Board
Foundation
Medicine
Board
W ti l t i ti f t i d t i l titi d iWe stimulate innovation, foster industrial competitiveness, and improve the quality of life.
Polymer Chemistry and Materials
Polymer physical chemistryMolecular design y p y yPolymer physicsProcessing
gMethodology development
Synthesis + characterization
PolymerPolymerChemistryChemistry
PolymerPolymerEngineeringEngineeringChemistryChemistry EngineeringEngineering
Nanoscience & Nanoscience & NanotechnologyNanotechnologyNanotechnologyNanotechnology
PhysicsBi l
FunctionM i l i
TechnologyTechnology InterdisciplinaryInterdisciplinaryinteractionsinteractions
BiologyMedicine
Materials propertiesProduct design
Create, study & apply functionalapply functional
polymeric(nano)materials with
new properties
Current Research Trends/Thrusts
Bio-Nanocomposites (Foster)Cellulose nanofibers as powerful filler for polymersCellulose nanofibers as powerful filler for polymers(NFP64, CTI, Industry)
Biomimetic Adaptive Nanocomposites (Foster)Materials that change mechanical props on commandMaterials that change mechanical props on command(NFP62, Industry)
Metallosupramolecular Polymers (Fiore, Simon)M h i f l l lMechanics of supramolecular polymersSelf-healing polymersOptical up-conversion(US Army, SNF)
Stimuli-Responsive Polymers (Weder)Chameleon polymers Mechanochemistry(Industry)
Nanostructured Materials (Geuss)Combine functional organic molecules with gconfinement effects in nanostructured hosts(NSF-DFG)
Current Research Trends/Thrusts
Bio-Nanocomposites (Foster)Cellulose nanofibers as powerful filler for polymersCellulose nanofibers as powerful filler for polymers(NFP64, CTI, Industry)
Biomimetic Adaptive Nanocomposites (Foster)Materials that change mechanical props on commandMaterials that change mechanical props on command(NFP62, Industry)
Metallosupramolecular Polymers (Fiore, Simon)M h i f l l lSmall amount of New functions throughMechanics of supramolecular polymersSelf-healing polymersOptical up-conversion(US Army, SNF)
Conventional Polymer Small amount offunctional additive
Creativeprocessing
New functions throughnano-scale effects
Stimuli-Responsive Polymers (Weder)Chameleon polymers Mechanochemistry
+processing
(Industry)
Nanostructured Materials (Geuss)Combine functional organic molecules with gconfinement effects in nanostructured hosts(NSF-DFG)
Nanofibers from NaturePoor Man’s Carbon Nanotubes
Super stiff cellulose nanofibers (“whiskers”, CW) can be extracted from a variety ofbio sources including wood cotton wheat straw animal tissue
Microcrystalline Cellulose Bundles
bio-sources including wood, cotton, wheat straw, animal tissue…
Native Material: Nanocomposite
Mechanical & ChemicalD d ti f A h
HydrolysisDegradation of Amorphous
CelluloseDispersion
Microcrystalline Cellulose NanofibersAmorphous Cellulose
Proteins
Individual CelluloseNanofibers
Weder et al. Biomacromolecules 2007, 8, 1353. Biomacromolecules 2009, 10, 712.
Nanofibers from Nature
Source Source• Availability
Native
Surface Chemistry
Availability• Dimensions(length reduction possible)
Many Alternate Sources-OH (-SO4
-)
Carboxylated
Many Alternate Sources
Carboxylated-COOH
A i t d Surface ChemistryAminated-NH2
Surface Chemistry• Processability• Compatibility w. polymers• Interactions
Alkylated-OCnHn+1
• Interactions
DimensionsStiffness
2200x25nm130 GPa
250x15nm105 GPa
150x15nm~80 Gpa
Borsali et al. Macromol. Rapid Commun. 2004, 25, 771.
Processing from ‘New’ Solvents
0.8 % TW Cellulose whiskers can be lyophilized & redispersed
N l t b d i ti d
Dispersions of freeze-dried re-dispersed TWs (5 mg/mL)
dispersion in H2O
New solvents broaden processing options and range of accessible nanocomposites
Dispersions of freeze dried, re dispersed TWs (5 mg/mL)Freeze dry
TW aerogel
H2O* H2O DMF DMSO NMP FA m-cresol
Re-disperse
0 8 % TWNMP Formic AcidWaterH2O H2O DMF DMSO NMP FA m cresol
*Not freeze-dried0.8 % TW
dispersion in solvent
l = 0.63 m l = 1.61 ml = 2.02 m
Turbak et al. US Patent 4378381 (1983). Dufresne et al. Macromolecules 2004, 37, 1386.Weder et al. Biomacromolecules 2007, 8, 1353; J. Mater. Chem. 2009, 19, 2118; ACS Appl.Interf. 2010, 2, 1073.
Processing from ‘New’ Solvents
Example: P(EO-EPI)/TW Nanocomposites made from a common solvent (DMF)
S l ti
+Cast, dry
C
Solution blending
0.1 % TW dispersion in
DMF
5 % w/w P(EO-EPI)in DMF
Compression mold (80C)0.5% w/w TW
in DMF5% w/w P(EO-EPI)
in DMFCH2 CH2 O
CH2 CH O
CH2Cl x y n
DMF
7988
109
At 25 CAFM SEM10 % w/w TW nanocomposite
1010
1011
E′ (P
a)
798 MPa
107
108
108
109
E' (
Pa)
0 % Filler 1 % Filler
5 % Fill
106
10 Dry 25 C Percolation
~1 MPaData fit percolation model: strongly
500 nm 1 m
-60 -40 -20 0 20106
107 5 % Filler
10 % Filler 15 % Filler 20 % Filler
Volume Fraction Filler0.00 0.05 0.10 0.15 0.20interacting 3-D nanofiber network
Weder et al. Nature Nanotech. 2007, 2, 765.
Temperature oC
Template Processing
Add non-solvent Supercritical
dryingAqueous nanofiber
dispersionNanofiber
gel
drying
N fibNanofiber aerogel
(E’=3.7 MPa)Imbibe with
polymer solution
109
107
108
G' (
Pa)
Dry, compression mold
Nanocomposite film
0.00 0.05 0.10 0.15 0.20 0.25 0.30106
Volume Fraction of Whiskers
Capadona, van den Berg, Rowan, Tyler, Weder Nature Nanotech. 2007, 2, 765. US Patent Application filed.
Tunicate Whisker Nanocomps
Shear storage moduli G’ of Polymer/TW nanocompositesPS @ 125CEO-EPI @ 25C
8
109
108
109
PS @ 125C
108
109
PBD @ 125C
107
108
G' (
Pa)
107
10
G' (
Pa)
106
107
G' (
Pa)
■ Template Approach ○ Solution Blending Percolation Model
0.00 0.05 0.10 0.15 0.20 0.25 0.30106
Volume Fraction of Whiskers
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18106
Volume Fraction of Whiskers
0.00 0.05 0.10 0.15 0.20 0.25105
Volume Fraction of Whiskers
■ Template Approach ○ Solution Blending ― Percolation Model
Nanocomposites made by Template Approach match P l ti M d l d l ti bl d d / lt d
Percolating nanocomposites only
accessible throughPercolation Model and solution-blended / melt processed materials
accessible through template approach!
Weder et al. Nature Nanotech. 2007, 2, 765. US Patent Application pending.
More Cellulose Nanocomps
Tunicate whisker / epoxy at 185 C Cotton whisker / epoxy at 185 C
109
Pa)
109
Pa)
312 MPa
2.4 GPa
108
E' (
P
108
E' (
P
16 MPa16 MPa
0.00 0.05 0.10 0.15 0.20 0.25 0.30107
Weight Fraction whisker0.00 0.05 0.10 0.15 0.20 0.25
107
Volume Fraction Whisker
Cellulose whisker / EO-EPI at 25 C Tunicate >> cotton (??)
108
Tunicate cotton (??)Cotton ~ MCC (some aggregation)
107
G' c
(Pa)
▲Cotton templateΔ Cotton cast● MCC template
0.0 0.1 0.2 0.3 0.4 0.5106
Volume Fraction of Whiskers
○ MCC cast
Weder et al. ACS Appl. Interf. 2010, 2, 1073.Weder et al. Biomacromolecules 2009, 10, 712.
Poor Man’s Carbon Nanotubes
Cellulose whiskers from renewable sources constitute an attractive, broadly , yuseful reinforcing filler material
Cellulose nanofibers can readily be processed by exploiting non-covalent interactions
Control over nanostructure is key to create materials with ultimate properties
Cellulose nanofibers represent an intriguing alternative to CNTs
Biomimetic Adaptive Materials
Sea cucumberDeep dermis features mutable mechanical propertiesproperties
Animal can reversibly switch the modulus of its skin between ‘soft’ and ‘rigid’ within microseconds
Relaxed Stiff
Low modulus matrix (collagen, fibrillin, H2O)
Relaxed Stiff
Switching through secretion ofstiffening proteins (tensilin) “on”“off”stiffening proteins (tensilin)
Effect is reversed throughproteinases
onoff
Peptide “cross-linkers”(Tensilin)
High modulus micro-fibers (collagen)
In vitro: 5 to 50 MPaCan we create artificial materials that mimic design and response?
Szulgit, Shadwick J. Exp. Biol. 2000. Trotter, Heuer et al. Biochem. Soc. Trans. 2000.
( )( g )and response?
Artificial Sea Cukes: Applications
Stimuli Relaxed Stiff
- Chemical - Electrical- Optical “on”“off”p- …
ApplicationsApplications
Cortical Interfacing
http://www.bioen.utah.edu/cni/projects/blindness.htm#overview
Modulus of Cortical Electrode Materials
Lifetime of Probes / Tissue Response (Gliosis)Improve the quality of life of patients that have
Modulus of Cortical Electrode Materials
10
12
14
(E) CD case
• Cellular Response to Implanted Material• Mechanical Mismatch -> Leading Hypothesis for• Micromotion chronic failure
p q y psustained central nervous system disability:
Spinal cord injury, head trauma, stroke, Parkinson’s disease2
4
6
8
Log
(
Rubber band
Jello
10 month explant: Dense fibrous network of
Mechanical Restrictions• Dura Mater (Stiffness E = 40 - 200 MPa) • Pia Mater (E=40 MPa) -> Need stiff probe to insert
B i Stiff 6 600 KP
disease...
Also: connect artificial organs (eye) to the brainKennedy et al IEEE Trans Rehabil Eng 2000 Hochberg et al
0
2
Dense fibrous network of neuroglia (supporting cells) • Brain Stiffness: 6 – 600 KPa Kennedy et al. IEEE Trans, Rehabil. Eng. 2000. Hochberg et al.
Nature 2006. Taylor et al. Science 2002. Santhanam et. al. Nature 2006. Nicolelis et al. Proc Natl Acad Sci USA, 2003.Ideal Adaptive Probe: Rigid for insertion, then soft(Water responsive)
Reverse Engineering the Cuke
CH2 CH2 O CH2 CH OLow modulus matrix (e.g.
EO EPI copolymer) CH2Cl x y n
Young’s Modulus E=0.3-3 MPaSlightly water-swellable (25 % @ rt)T 37 ºC
Relaxed Stiff
EO-EPI copolymer)
Tg = -37 ºC“on”“off”
Cross-linking through h d b di
High-modulus nano-fib ( ll l )
Turn off hydrogen bonding through
hydrogen bondingfibers (cellulose)competitive interactions with H2O
T ff HOH OH
Turn off H-bonding
OOHO
OH
O
O
HOOH
OSO3
n
Weder et al. Nature Nanotech. 2007, 2, 765. Biomacromolecules 2007, 8, 1353 & 2009, 10, 712.Capadona, Shanmuganathan, Tyler, Rowan, Weder Science 2008, 319, 1370. Weder et al. US Patent Applications pending.
Mechanical Properties - Models
Percolation model
“complete interconnected networkof fillers within the matrix”
“percolation on”
Takayanagi et al. J. Polym. Sci. 1964, C5, 113. Ouali et al. J.
p
y g y , ,Plast. Rubber Comp. Process. Appl. 1991, 16, 55. Halpin, Kardos J. Appl. Phys. 1972, 43, 2235. Hajji et al. Polym. Comp.1996, 17, 612. Polymer Eng. Sci. 1997, 37, 1732.
Halpin-Kardos / Halpin-Tsai: Mean field approach
“fibers are smeared into thematrix to form a homo-
ti ”
0o
45o
90o geneous continuum”90o
-45o“mean field / percolation off”
Mechanical Properties - Models
109 (1 - 2r)EsEr + (1 - r) Er2
(1 )E + ( )EE′ =Percolation
108
Pa)
(1 - r)Er + (r – )Es
= rr - c - c
Halpin-Kardos0.4
107
E' (
P
E′ = 4U5(U1 –U5)/U1U1 = 1/8(3Q11 + 3Q22 + 2Q12 + 4Q66)
c
All components can be experimentally determined:
0.00 0.05 0.10 0.15 0.20106
U5 = 1/8(Q11 + Q22 – 2Q12 + 4Q66)
Q11 = EL/(1 – 12 * 21)
Q22 = ET/(1- 12 * 21)
E’ = Tensile storage modulus of compositeE’s = Tensile storage modulus of soft phaseE’ = Tensile modulus rigid phase (4 8 GPa*) Volume Fraction Filler
Tensile storage modulus E’ of nanocomposite depends on
Q12 = 12 * Q22 = 21 * Q11
Q66 = G12
12 = f * f + m * m
E r = Tensile modulus rigid phase (4-8 GPa )r = volume fraction of rigid phasec = critical volume fraction f. percolation = 0 7/f f = aspect ratio L/d = 84nanocomposite depends on
nanofiber concentration and connectivity between nanofibers
G12 = Gm(1 + * f)/(1 – * Xf)
= (Gf/Gm – 1)/(Gf/Gm + 1)
ET = Em(1+ 2 * T * f)/(1 – T * f)
c = 0.7/f, f = aspect ratio L/d = 84
E′ = 2G′(n + 1), n = Poisson’s ratio = 0.3 G’ = Shear storage modulus of compositeT = ((Etf/Em) – 1)/(Etf/Em) + 2)
EL = Em(1 + 2(L/D) L * f)/(1 – L * f)
L = ((Elf/Em) – 1)/((Elf/Em) + 2(L/D))
Takayanagi et al. J. Polym. Sci. 1964, C5, 113. Haji et al. Polym. Comp. 1996, 17, 612. *To be discussed…
(in epoxy matrix E’r = 24 Gpa)
P(EO-EPI)/TW Nanocomposites
109 798 MPaDry vs. water-swollen @ 23C
108
798 MPa
107
E' (
Pa)
22 MPa
106
0.7 MPa0.00 0.05 0.10 0.15 0.20
Volume fraction filler
• Stiffness decreases dramatically (40x) upon swelling with water or ACSF
Water
• “On” moduli match Percolation Model, “Off” moduli approach Halpin-Kardos Model, Effect is fully reversible (supports proposed mechanism)
• Mechanical contrast too low for cortical electrodes
Capadona, Shanmuganathan, Tyler, Rowan, Weder Science 2008, 319, 1370.
PVAc/TW Nanocomposites
Dry Nanocomposites
5 1 GP 400
ACSF Swollen Nanocomposites
5.1 GPa
1.8 GPa
4.8 GPa
OAc300
350
400 16.5 % v/v whiskers 12.2 % v/v whiskers 8.1 % v/v whiskers 4.0 % v/v whiskers 0.8 % v/v whiskers 0.0 % v/v whiskers
156 MPan
Poly(vinylacetate)150
200
250
E'(M
Pa)
Poly(vinylacetate)
0
50
100
Use PVAc as matrix: Tg ~42°C; minimal aqueous swelling (4.5%)
20 30 40 50 60
Temperature (°C)
Softening temperature increases above physiological temperature
Exposure to water plasticizes nanocomposites, drops Tg and switches TW-TW
Capadona, Shanmuganathan, Tyler, Rowan, Weder Science 2008, 319, 1370. Progr. Polym. Sci. 2010, 35, 212.
interactions off: Rapid mechanical switching from GPa to MPa range
Switching in Vitro
Properties of 12% v/v PVAc/TW Nanocomposites
In ACSF
p p
40 MPa 12 MPa40 MPa 12 MPa
Capadona, Shanmuganathan, Tyler, Rowan, Weder Science 2008, 319, 1370.Shanmuganathan, Capadona, Rowan, Weder Progr. Polym. Sci. 2010, 35, 212.
First Cortical Electrodes
Solution Blend Nanocomposite
Insulator (PPX)
Patterned conductor (Gold)
n Compression mold film
Adaptive Nanocomposite
Patterned conductor (Gold)
Insulator (PPX)Fabricate inserts
CVD PPXLaser-cut
Micro-machined
Sputter gold
machined
Hess, Dunning, Harris, Capadona, Shanmuganathan, Rowan, Weder, Tyler, ZormanIEEE Proceedings, Transducers 2009.
Animal Model
100 fil
Cut through soft tissue and expose skull
Drill through skull to expose cortical tissue
Insert probes into the cortical tissue
100 m film
Dissolve glucose with saline, seal hole.
NC = 12.2% v/v TW in PVAc
Wire = 300 m Tungsten dip coated with PVAc
Chronic Implantation - Histology
Activated Microglia / Macrophages (ED1)
Neuronal Nuclei (NueN)Macrophages (ED1)
NC
ated
P
VAc
Coa
Wire
P
Adaptive nanocomposites cause less inflammation and support a more stable neural integration
Harris, Capadona, et al. (unpublished)Harris, Capadona, Shanmuganathan, Rowan, Weder, Zorman, Tyler submitted.
support a more stable neural integration.
Electrophysiology
Waveforms sampled at 24 4 kHz Interspike Interval12 % v/v PVAc/TW Nanocomposites
0 50 100 150 200 250 300 350-200
0
200
Waveforms, sampled at 24.4 kHz Interspike Interval Histogram
Nanocomposites
115 115.5 116 116.5 117 117.5 118 118.5 119 119.5 120-50
0
50
0
50
(μV)
116 8 116 85 116 9 116 95 117 117 05 117 1-50
0
50116 116.2 116.4 116.6 116.8 117 117.2 117.4 117.6 117.8 118
-50
0
Sign
al
1880 spikes with all intervals above 3 ms
116.8 116.85 116.9 116.95 117 117.05 117.1
116.95 116.951 116.952 116.953 116.954 116.955 116.956 116.957 116.958 116.959 116.96-50
0
50
Time (s)
2 Week nanocomposite 200 m
( )
Single Unit Activity Recording
2 Week nanocomposite 200 m
Hess, Dunning, Harris, Capadona, Shanmuganathan, Rowan, Weder, Tyler, ZormanIEEE Proceedings, Transducers 2009.
Biomimetic Adaptive Materials
Copying the sea cucumber’s cool trick has allowed for the creation of a new py gfamily of chemo-responsive, mechanically adaptive materials
Mechanically adaptive polymers appear to be useful for cortical electrodes and many other applications
Nanostructured Systems
Key Feature of Nanostructured Systems: InterfacesOptical Processes: Reflection and RefractionOptical Processes: Reflection and Refraction
n
transmitted
incidentn2
n1
= 2(n d + n d ) n2 d2
reflected
n1 d1
transmittedn1
refl = 2(n1d1 + n2d2)
Responsive Nanostructures
Key Feature of Nanostructured Systems: InterfacesOptical Processes: Reflection and Refraction
The unusual optical properties of nano-structured
Optical Processes: Reflection and Refraction
materials make them attractive for optical compo-nents such as waveguides, dielectric mirrors…
The functionality of such systems could be dramati-cally broadened if functional polymers were used:cally broadened if functional polymers were used:
- Photo-reactive - Fluorescent- Nonlinear optical- Other
Tangirala, Baer, Hiltner, Weder Adv. Funct. Mater. 2004, 14, 595.
Multilayer Polymer Coextrusion
E. Baer, A. Hiltner et al.Macromol. Rapid. Comm. 2003, 24, 943.
Layer Multiplication
Surface Layer
Surface LayerSurface Layer
•Continuous melt process•Coextrude two immiscible polymers•Produce a single film with many (4 – 4096) individual layers (m – nm)•Films are1D photonic crystals; reflection band can be tuned over broad range
Multilayer Polymer Coextrusion
128 layered PS/PMMA photonic films (average layer thickness = 86 nm)
Proc. SPIE 2009, 7467, 74670A.
Distributed Feedback Laser
Distributed Feedback (DFB) Lasers
Laser in which the gain medium is an integral part of the cavity. The opticalfeedback is achieved by optical interference in the periodic structurecontaining the gain mediumcontaining the gain medium. All-plastic, laser structure produced by
multilayer coextrusionPhotonic bandgap corresponds to-Photonic bandgap corresponds to fluorescence emission peak
-Fluorescent dye in every other layer, feed-back and gain provided by the same structure
J. Mater. Chem. 2009, 19, 7520.
Distributed Feedback Laser
128 Layers of poly(styrene-co-acrylonitrile) (SAN25, n = 1.56) doped with 1%C1-RG and fluoroelastomer THV (n = 1 37 terpolymer of tetrafluoroethyleneC1-RG and fluoroelastomer THV (n = 1.37, terpolymer of tetrafluoroethylene,hexafluoropropylene and tetrafluoroethylene ) Overall thickness = 12 m
AbsAbs PL
sorb
ance
(a.u
.)
Inte
nsity
(a.u
.)
400 500 600 700
Abs
Wavelength (nm)
PL
OMeMeO
CN
OMe
CN
OMe Slope Efficiency: 0.25%Threshold: 104 J/cm2
J. Mater. Chem. 2009, 19, 7520.
Teaching Polymers New Tricks
ConventionalPolymer
Small amount offunctional additive
New functions through nano-scale effects
+
Polymer functional additiveCreative
processing
scale effects
Acknowledgments
Graduate StudentsMahesh BiyaniM k B thMark Burnworth Souleymane CoulibalyMehdi JorfiSonja KrachtS H LSoo-Hyun LeeJoe Lott Brian MakowskiBastian Schyrr
Postdocs / Group LeadersDr. Gina FioreDr. Johan FosterDr. Markus GeussDr. Lorraine Hsu Dr. Prathip KumarDr. Sandeep KumarDr. Yoan Simon
Collaborations: Profs. Jim Andrews, Eric Baer, Phil Castellano, J. Capadona, S. Eichhorn, Anne Hiltner, S. Rowan, Jie Shan, Ken Singer, D. Tyler, C. Zorman
Current FundingAM Foundation Army Research Office (DAAD19-03-1-0208)DuPont Firmenich Goodyear NSF CBET 0828155 DMR 0804874
Dr. Liming Tang Alumni: Drs. Otto van den Berg, Julie Mendez, Kadhiravan Shanmuganathan, Ravi Tangirala
DuPont , Firmenich, Goodyear NSF CBET-0828155, DMR-0804874Michelin STC Center CLiPS (DMR 0423914)SNF (R’Equipe, NFP 62) NSF MWN (DMR-062767)CTI/3D-Systems NIH (5R21NS053798)
