Nanolatex-Based Nanocomposites: Control of Filler Structure and Reinforcement

1. Nanolatex based nanocomposites: control of the filler structure and reinforcement . A. Banc 1 * , A-C. Genix 1 , C. Dupas, M. Chirat 1 , S.Caillol 2 , and J.Oberdisse 1 1 Laboratoire Charles Coulomb, Universit Montpellier 2, Montpellier, France 2 Institut Charles Gerhardt, Montpellier, France

2. Mechanical reinforcement in nanocomposites ? M ICROSTRUCTURE Filler network Diluted regime Filler Percolation threshold Composite properties Filler properties + Matrix properties M ECHANICAL PROPERTIES Jouault et al. F ILLER - FILLER INTERACTIONS F ILLER - MATRIX INTERACTIONS

3. Model nanocomposites with tunable filler structure si30 nm Collodal silica + Drying Annealing Water evaporation Particles deformation Polymer diffusion Nanocomposite TUNABLE nanostructure: f( Si , Si / PEMA , M w ) PolyEthylMethacrylate (PEMA) Tg>Tamb Nanolatex PEMA 30 nm OR 200nm Mw 20, 50 or 160 kg/mol

4. E FFECT OF R latex / R si

5. Small Angle Scattering k i k s Wave vector q= - k s k i I(q)= f( , , P(q), S(q)) = Volume fraction = Scattering objects - matrix = Scattering lengh density P(q) = Form factor S(Q)= Structure factor q( -1 ) P(q) S(q) I(q) Silica nanoparticles P(q) =14 nm =0,11 q max d P(q)*S(q) q -df df= fractal dimension

6. 0% 1% 3% 5% 10% Structure R silica ~R latex ~14 nm Q -2,4 Colloidal solutions R silica <

7. 5m 500nm 5m 5m 5m 500nm R silica ~R latex ~14 nm R silica <

8. Rheological properties G G G G G G G G Matrix 10% nanocomposite Silica structure little impacts G at low frequency (long times) N O IMPORTANT EFFECT OF THE SILICA STRUCTURE ON RHEOLOGICAL PROPERTIES ( Low strain: 0,2% ) x4

9. E FFECT OF THE MATRIX M W

10. Structure: SAXS Mw= 160 000g/mol 50 000g/mol 20 000g/mol 10% 5% 3% 1% Matrix Well dispersed filler Fractal aggregates d f =2,4 d f =2,3 Bigger fractal aggregates R silica ~R latex ~14 nm

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

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

13. Structure: 10% nanocomposites d* d* d* d*=2 /q* Model cubic network Silica networks whose the characteristic size decreases with Mw => decrease of the wall thickness 20 000g/mol 50 000g/mol 160 000g/mol

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

15. Rheological properties: matrices PEMA160 PEMA50 PEMA20 G G G G G G G N Master curve at annealing temperature (180C): Filler mobility: PEMA20 > PEMA50 > PEMA160

16. Rheological properties: nanocomposites Two filler volume fraction regimes: - < threshold viscoelastic material - > threshold elastic material Filler effect: -G at low frequency threshold <10%

17. At < threshold G~ 1/(3-df) G~ 1,7 Aggregate fractal dimension: df=2,4 (SAXS) Reaction Limited Aggregation -Slow aggregation In the weak-link regime : Shih et al, 1990 Rheology of fractal objets

18. d* d* d* At > threshold Fractal aggregates reinforce much more than the well dispersed filler . Power law ?

19. Conclusions - Prospects => Dynamical approaches of the mechanical reinforcement Model nanocomposites Various nanoparticle dispersions: well dispersed / fractal aggregates / porous network => Novel structures with mixtures of latex bead sizes Mechanical reinforcement Mostly at low frequency aggregated filler reinforce better than the well dispersed one Quantitative description of the filler structure : D IRECT SPACE R ECIPROCAL SPACE TEM SAXS Image analysis + Simulation => Behavior at large strains?