Gradient of glass transition temperature in filled elastomers

By studying model systems consisting of poly( ethyl acrylate) polymer chains covalently bound to silica particles, we show here how the temperature dependence of the modulus of filled elastomers can be explained by a long-ranged gradient of the polymer matrix glass transition temperature in the vicinity of the particles. We are led to this conclusion by comparing NMR and mechanical data. We show thereby that the mechanisms of reinforcement are the same as those which lead to an increase of the glass transition temperature of strongly adsorbed thin polymer films. It allows us in particular to propose a new time-temperature superposition law for the filled elastomers viscoelasticity.