POLYMER DIFFUSION IN SEMICRYSTALLINE POLYMERS .2. ATACTIC POLYSTYRENE-D TRANSPORT INTO ATACTIC AND ISOTACTIC POLYSTYRENE

The transport of monodisperse, atactic polystyrene-d (aPS-D) into atac tic polystyrene (aPS) melts and isotactic polystyrene (iPS) semicrysta lline matrices has been characterized by a quantitative ATR-FTIR techn ique.; Values of aPS-D tracer diffusion coefficients in aPS melts comp are very well with previous literature indicating the effects of (i) d iffusant molecular weight holding constant the matrix molecular weight and (ii) matrix molecular weight holding constant the diffusant molec ular weight. Semicrystalline morphologies of iPS were characterized ex tensively by DSC, microscopy, and SAXS as a function of temperature. N on-Fickian transport kinetics are observed during the imbibition of aP S-D into semicrystalline iPS at low temperatures and high penetrant mo lecular weights. There are two apparent time regimes of non-Fickian ki netics. The first regime of imbibition kinetics occurs at early times, where the uptake can be described by Fickian mutual diffusion kinetic s. Later, there is a decrease in the imbibition rate and the rates of continued imbibition are no longer Fickian. The transition to a slower transport kinetics regime can be identified with a time scale over wh ich penetrant macromolecules in amorphous pockets explore the bottlene cks between crystalline, dendritic obstacles.