Segmental dynamics and linear rheology of nearly athermal all-polystyrene nanocomposites

Abstract Nanoparticles impact on segmental dynamics and rheology of polymers while the mechanisms are far from being clarified. Herein nearly athermal nanocomposites composed of crosslinked polystyrene (cPS) nanoparticles dispersed in linear polystyrene were investigated. The crosslinking degree and thus rigidity of cPS nanoparticles of the same size are found to play an important role in affecting the segmental relaxation and rheology of the nanocomposites. While scarcely crosslinked nanoparticles depress glass transition temperature and accelerate segmental relaxation of the matrix markedly, these effects become negligible for highly crosslinked nanoparticles. On the contrary, the reinforcement becomes increasingly large with increasing crosslinking degree of cPS nanoparticles. Increasing the content of the highly crosslinked nanoparticles may cause a transition from Vogel-Fulcher-Tammann to Arrhenius-like temperature-dependence of segmental relaxation for the frustration of intermolecular coupling. The improvement of reinforcement factor with increasing nanoparticle crosslinking degree is well explained by a modified Mooney equation and is associated to the enlarged local strain and retarded terminal relaxation of the matrix.