Recent progress in the filler microstructure and the dynamical properties of polymer nanocomposites of industrial relevance is reviewed. We focus mainly on systems used in car tire treads made of styrene-butadiene rubber (SBR) matrices in which precipitated amorphous silica like Zeosil® with a complex multi-scale structure is dispersed—while occasionally comparing to other experimental systems, including model studies with well-defined colloidal silica nanoparticles. Electron microscopy and small-angle scattering—namely SAXS and SANS—are powerful methods of structural analysis, and some recent developments including the correlation hole analysis giving access to local aggregate properties or reverse Monte Carlo approaches providing aggregate distribution functions are discussed. The dynamical response of such complex systems is then studied by broadband dielectric spectroscopy (BDS), starting from the individual components. Maxwell–Wagner–Sillars interfacial polarization processes including charge and water migration are shown to be able to probe large-scale microstructure, evidencing filler percolation effects as observed in rheology. Then, BDS is shown to be highly suitable for studies of the evolution of the segmental dynamics of rubber, giving insight into vulcanization mechanisms under the effect of industrial additives, as well as in transitions from heterogeneous to homogeneous dynamics of polymer blends. Finally, the difficulties of investigating segmental dynamics in industrially relevant filled systems by BDS are critically discussed, and some recent neutron spin echo results are reported evidencing only a small impact of filler surfaces on segmental dynamics in weakly interacting SBR-silica systems.

Wheat gluten includes two major proteins classes, gliadin (25–60 kg/mol) and glutenin polymers (100 to > 2,000 kg/mol) each comprising several polypeptides routinely identified by size-exclusion chromatography and electrophoresis. Gluten proteins are rich in glutamine (30%) and contain several repeated sequences, linking them to the wide class of intrinsically disordered protein (IDP). Here we showed that an ethanol/water (EtOH/W, 50/50, v/v) extract of an industrial gluten, comprising 1/3 of glutenin polymers and 2/3 of gliadin, underwent liquid-liquid phase separation (LLPS) below 14 °C, leading to two coexisting phases, respectively rich and poor in protein. As the quenching depth increased, proteins of lower and lower molecular weight joined the rich phase, akin to what would have been obtained for a polydisperse polymer sample. Within the rich phase the mass ratio of glutenin over gliadin decreased from 2.5 to 0.5 as the temperature dropped from 14 °C to −0.8 °C. Concomitantly the concentration in glutenin polymers increased up to 143 ± 6 g/L (at 9 °C) and then stopped to evolve, suggesting that the binodal line intersected the gelation line below this temperature. Applying the Flory-Huggins (FH) lattice model for each gluten protein classes, we demonstrated that their partitioning in the coexisting phases followed a same temperature dependency. However, some gliadin species joined the rich phase above their critical temperature. Here, specific interactions with the glutenin polymers through weak forces were exemplified. The study demonstrated the relevance of the Flory-Huggins (FH) lattice model in predicting phase behavior even when applied to complex protein mixtures.

Both an experimental and a theoretical investigation of the fracture propagation mechanisms acting at the process zone scale in glassy polymers are presented. The main aim is to establish a common modeling for different kinds of glassy polymers presenting either steady-state fracture propagation or stick-slip fracture propagation or both, depending on loading conditions and sample shape. On the experimental point of view, new insights are provided by in-situ AFM measurements of the viscoplastic strain fields acting within the micrometric process zone in a brittle epoxy resin, which highlight an extremely slow unexpected steadystate regime with finite plastic strains of about 30% around a blunt crack tip, and accompanied by propagating shear lips. On the theoretical point of view, we apply to glassy polymers some recently developed models for describing soft dissipative fracture that are pertinent with the observed finite strains. We propose a unified modeling of the fracture energy for both the steady-state and stick-slip fracture propagation based on the evaluation of the energy dissipation density at a characteristic strain rate induced in the process zone by the competition between the crack propagation velocity and the macroscopic sample loading rate.