DYNAMIC STUDY OF POLY(STYRENE-VINYL-D3) IN A GLASSY BLEND BY 2-DIMENSIONAL SOLID-STATE DEUTERON NMR

Reorientation of the polystyrene component in a compatible blend of polystyrene and poly(2,6-dimethylphenylene oxide) with 75 % polystyrene was observed by two-dimensional solid-state deuteron NMR spectroscopy at the glass transition. A blend containing poly(styrene-vinyl-d3) was studied as a function of temperature and mix time in the vicinity of the thermal glass transition. Chain motion of the deuterium-labeled polymer exhibited the characteristics of rotational Brownian diffusion with an associated broad distribution of correlation times. This distribution is considerably broader than that typical for single-component polymeric glasses and dynamically matches that previously observed for the chain motion of the other component in this particular blend. The dynamics of either component can only be simulated using a bimodal distribution, with each mode involving a distribution of correlation times. The relative weighting of the modes corresponded to local concentration fluctuations calculated using a statistical lattice model. This dynamic heterogeneity for both components in the blend is thus determined by the surroundings of the reference chain and not by the intrinsic dynamics of a given chain.