Morphology, thermal properties and molecular dynamics of syndiotactic polystyrene (s-PS) nanocomposites with aligned graphene oxide and graphene nanosheets

In this work we report morphological, calorimetric and dielectric results for polymer nanocomposites (PNCs) based on syndiotactic polystyrene (s-PS) filled with graphene oxide (GO) and graphene by employing melt-mixing. The preparation of the PNCs resulted in aligning of the filler in the polymer matrix as observed by SEM and Wide Angle X-ray Scattering (WAXS). Weak polymer-filler interactions were found, opposite to what has been reported in the literature for atactic polystyrene PNCs. Results by calorimetry (DSC) revealed an increase in crystallization temperature of s-PS upon filler addition, suggesting that the fillers offer additional sites, nuclei, for crystallization. At the same time, filler content has no significant effects on crystalline fraction. The glass transition temperature, T_g, decreases slightly in PNCs, most probably, due to loosened molecular packing of the polymer chains. Taken these results together with those for the calculated rigid amorphous fraction (RAF), which does not vary in a systematic way with the filler loading, we suggest that RAF correlates better with the polymer being bound around the crystals rather than that at the surfaces of the fillers. In dielectric spectroscopy (DRS) next to the main segmental α relaxation of bulk s-PS, related to the glass transition, an additional filler-related relaxation (α′) was recorded in the PNCs.