Segmental dynamics of dilute polystyrene chains in miscible blends and solutions

H-2 NMR relaxation time measurements have been used to investigate the segmental dynamics of polystyrene chains in six miscible polymer blends in the limit of low polystyrene concentration. These data are combined with previously reported results for the segmental dynamics of dilute polystyrene chains in four solvents. Polystyrene dynamics in these 10 hosts are strongly correlated with the glass transition temperature T, of the host, but the dilute chain dynamics are not slaved to the host matrix dynamics. The Lodge-McLeish model, using a single value for the self-concentration phi(self) = 0.35, reasonably describes polystyrene segmental dynamics in all 10 hosts and also describes previously reported dynamics of dilute polyisoprene chains in four miscible blends. The dilute polystyrene segmental dynamics can be more accurately described if phi(self) is allowed to depend on blending partner, with the resulting variation of phi(self) from 0.14 to 0.48.