Nanolatex based nanocomposites : control of the filler structure and reinforcement .

1. Nanolatex based nanocomposites: control of the filler structure and reinforcement. A. Banc1*, A-C. Genix1, C. Dupas, M. Chirat1, S.Caillol2, and J.Oberdisse1 1Laboratoire Charles Coulomb, Université Montpellier 2, Montpellier, France 2 Institut Charles Gerhardt, Montpellier, France

2. σ λ Mechanicalreinforcement in nanocomposites ? Microstructure Mechanicalproperties Composite properties ≠ Filler properties + Matrixproperties Percolation threshold • Filler-filler interactions • Filler-matrix interactions FFiller Filler network Dilutedregime Jouault et al.

3. Model nanocompositeswithtunable filler structure Colloïdal silica Nanolatex + Øsi≈30 nm PolyEthylMethacrylate (PEMA) Tg>Tamb ØPEMA≈30 nm OR 200nm Mw ≈ 20, 50 or 160 kg/mol Drying Water evaporation Annealing Particlesdeformation Nanocomposite Polymer diffusion TUNABLE nanostructure: f(FSi, ØSi/ØPEMA, Mw )

4. Effect of Rlatex/Rsi

5. Small Angle Scattering S(q) P(q) I(cm-1) I(q) ks ki l ki ks Wavevector q= - q(Å-1) I(q)= f(F, Dr, P(q), S(q)) F= Volume fraction Dr=rScatteringobjects-rmatrix r=Scatteringlenghdensity P(q) = Form factor S(Q)= Structure factor Silicananoparticles P(q) P(q)*S(q) q-df df= fractal dimension d qmax <R>=14 nm s=0,11

6. Structure Colloidal solutions Rsilica~Rlatex~14 nm Rsilica<<Rlatex~100 nm Latex nanoparticles d*=196 nm Silicananoparticles d**=27 nm Q-2,4 Q-3 ● 0% ● 1% ● 3% ● 5% ● 10% Lowsilicaaggregation Fractal aggregates Template effect of the latex Structuredporous network

7. Rsilica~Rlatex~14 nm Rsilica<<Rlatex~100 nm 1% 1% Heterogeneous 10% 10% 5µm 5µm 5µm 5µm 500nm 500nm

8. Rheologicalproperties Matrix 10% nanocomposite G’ G’ G’’ G’’ x4 G’’ G’’ G’ G’ Silica structure little impacts G’ atlowfrequency (long times) No important effect of the silica structure on rheologicalproperties (Lowstrain: 0,2%)

9. Effect of the matrix Mw

10. Structure: SAXS Rsilica~Rlatex~14 nm 10% 5% 3% 1% Matrix df=2,3 df=2,4 Mw= 160 000g/mol 50 000g/mol 20 000g/mol Bigger fractal aggregates Fractal aggregates Welldispersed filler

11. Structure: TEM 1% 3% 10% PEMA20 PEMA50 500 nm PEMA160

12. Structure: Monte Carlo simulation 1% nanocomposites: No inter-aggregate structure factor 160 000g/mol 20 000g/mol <Nagg>=3 <Nagg>=51 Kappa>20% Kappa=12.5% Image analysis Monte Carlo simulation Correlation direct space and reciprocalspace via simulation

13. Structure: 10% nanocomposites 20 000g/mol 50 000g/mol 160 000g/mol d* d* Model cubic network d* d*=2P/q* Silica networks whose the characteristic size decreaseswithMw => decrease of the wallthickness

14. Structure: overview <Nagg=51> K=12% d* 1% 3% 10% df=2,4 PEMA20 d* df=2,3 PEMA50 <Nagg=3> K>20% d* 500 nm PEMA160

15. Rheologicalproperties: matrices Master curveatannealingtemperature (180°C): GN G’’ G’ PEMA160 PEMA50 PEMA20 G’’ G’ G’ G’’ PEMA criticalentanglement mass: Mc=~13,5 kg/mol (PEMA20: Mn=10,7kg/mol Mw=18,5kg/mol) Filler mobility: PEMA20 > PEMA50 > PEMA160

16. Rheologicalproperties: nanocomposites Two filler volume fraction regimes: -F<Fthresholdviscoelasticmaterial -F>Fthresholdelasticmaterial Filler effect: -G’ atlowfrequency 5%< Fthreshold<10%

17. AtF<Fthreshold • Aggregate fractal dimension: • df=2,4 (SAXS) • Reaction Limited Aggregation • -Slow aggregation In the weak-linkregime: G’~φ1/(3-df) G’~φ1,7 Rheology of fractal objets Shih et al, 1990

18. d* d* AtF>Fthreshold d* Power law ? Fractal aggregatesreinforcemuch more than the welldispersed filler.

19. Conclusions - Prospects • Model nanocomposites • Variousnanoparticledispersions: welldispersed / fractal aggregates / porous network => Novel structures with mixtures of latex bead sizes • Quantitative description of the filler structure : Direct space Reciprocalspace SAXS TEM Image analysis + Simulation • Mechanicalreinforcement • Mostlyatlowfrequency – aggregated filler reinforcebetterthan the welldispersed one => Behaviorat large strains? … => Dynamicalapproaches of the mechanicalreinforcement