Segmental Relaxation of Poly(styrene-co-vinylphenol)

ABSTRACT: Dielectric and mechanical measurements of the R-relaxation are reported for polystyrenes of varying vinylphenol content. The presence of the polar moiety substantially increases both the glass transition temperature and the segmental relaxation times of the polymer. However, the shape of the relaxation function, as well as the temperature dependence of the relaxation times, is invariant to copolymer composition. This indicates that the enhanced interactions arising from polar modification of the polystyrene are short-lived on the time scale of the segmental dynamics. Although fragility was found to be independent of copolymer composition, the heat capacity change at Tg increases with increasing vinylphenol content. The absence of a correlation between these two quantities is contrary to an energy landscape interpretation of fragility