Constrained Dynamics in interphases of model filled elastomers : role of interface chemistry on crosslinking, local stress distribution and mechanics – DINaFil

The objective of this project is to realize a breakthrough in the understanding of the reinforcement of filled elastomers in the linear and non-linear regimes of deformation, as a function of the strength and/or nature of the filler-matrix interactions. Specifically, we aim at understanding comprehensively the nature of the slow dynamics of the polymer at the particles interface and its role as regards the physical properties. We will elaborate new and unique model systems based on poly(isoprene) and silica, designed to be both well controlled and close to ?real-life’ reinforced elastomers. The systems will be based on innovative dispersion procedure of the silica fillers using transfer in solvent, plus taylored surface chemistry and/or physico-chemistry of the silica fillers to control the interactions at filler-matrix interfaces in a very sensitive way. In this way, we aim at controlling both the nature and strength of surface interactions and the quality of the silica dispersion. We will study the mechanical properties extensively at small strain amplitudes (linear regime), intermediate amplitudes (Payne effect) and large amplitudes (Plastic behaviour, Mullins effect, second Payne effect). Mechanical measurements will be combined with in-situ microscopic measurements (small angle scattering, NMR). Small angle scattering measurements will be used to characterize the dispersion. Mechanical and dielectric spectroscopy will be used to characterize the dynamical state of the elastomer matrix. We will combine three innovative developments. 1) To get a very detailed insight into the behaviour of the elastomer matrix, we will use and/or develop advanced, innovative NMR methods which give access to local crosslink density heterogeneities and dynamical heterogeneities. 2) In order to provide a quantitative link between the physics of filled elastomers and thin films dynamics, and thus help unifying both domains, we will push further the development of new, multiscale modelling methods able to reach both spatial and time scales relevant to the physics of thin films dynamics and of filled elastomers. 3) We will perform small angle scattering and NMR measurements in systems stretched in-situ at medium to large strain amplitudes, to get a detailed insight into the local deformation mechanisms. Finally, the aim of the project is to predict mechanical properties as a function of the tailored surface treatments, from the linear up to the non-linear (Plasticity, Mullins effect, second Payne effect) which will pave the way for designing filled elastomers with tailored properties. The innovations proposed in this project (tayloring interfaces, combining mechanical properties and detailed microscopic studies, including microscopic studies of stretched samples, multi-scale modelling) strongly rely on recent works and results of the participating groups, that will be combined and developed much further thanks to this project.