Segmental relaxation of poly(styrene-co-vinylphenol)

Dielectric and mechanical measurements of the alpha-relaxation are reported for polystyrenes of varying vinylphenol content. The presence of the polar moiety substantially increases both the glass transition temperature and t he segmental relaxation times of the polymer. However, the shape of the rel axation function, as well as the temperature dependence of the relaxation t imes, is invariant to copolymer composition. This indicates that the enhanc ed interactions arising from polar modification of the polystyrene are shor t-lived on the time scale of the segmental dynamics. Although fragility was found to be independent of copolymer composition, the heat capacity change at T-g increases with increasing vinylphenol content. The absence of a cor relation between these two quantities is contrary to an energy landscape in terpretation of fragility.