Molecular Dynamics in Poly(Methyl Methacrylate)/Silica Nanoparticle Composites*

Broadband Dielectric Spectroscopy (BDS) and Differential Scanning Calorimetry (DSC) are employed to study molecular dynamics and glass transition temperature (Tg) in poly(methyl methacrylate) (PMMA)/Silica-nanoparticle (NP) composites. By systematically probing the case of bare (non-functionalized) Si-NPs dispersed in PMMA matrix and that of PMMA grafted Si-NPs in PMMA matrix, we isolate the effects of each of these cases on dynamics and Tg. Furthermore, we show – for the structural relaxation process – that in addition to slowed down mobility, which is commonly reported in literature and assigned to dynamics at the NP-matrix interface, faster modes also arise due to confinement effects. Scanning Electron Microscopy (SEM) is used to confirm uniform dispersion of the NPs.