CRYSTALLIZATION AND MORPHOLOGY OF POLY(ARYLENE ETHER ETHER SULFIDE)S - DUAL SPHERULITIC MORPHOLOGY

Spherulitic growth rate and morphological studies carried out on a nov el poly(ether ether sulfide) yielded dual spherulitic morphologies at all crystallization temperatures. Distinct populations of two kinds of spherulites were formed, with a population of coarse-textured spherul ites exhibiting higher growth rate (Type II) than a population of fine -textured spherulites (Type I), at all temperatures studied. The growt h rate dependence on temperature for the Type I spherulites was consis tent with the theoretically predicted ''bell-shaped'' curve, indicatin g nucleation-controlled growth at temperatures close to the melting te mperature and diffusion-controlled growth at temperatures closer to th e glass transition temperature. The growth rate of the Type II spherul ites, however, surprisingly did not exhibit any diffusion-controlled r egime, with the growth rate increasing with decreasing temperature acr oss the whole range of temperatures studied here. The above described phenomenon was found to be independent of the prior melt and crystalli zation history and nature of the substrate in all cases except one. Th e morphology of the different spherulites has been studied with a comb ination of optical microscopy, scanning electron microscopy, and atomi c force microscopy. The Type II spherulites exhibited a coarser and mo re ''open'' morphology, with thicker bundles of fibrils and large inte rfibrillar gaps, radiating outward from the center of the spherulite. The Type I spherulites were found to exhibit curvature indicative of s pherical behavior, whereas the Type II spherulites appeared to exhibit a flat disklike appearance; this finding is consistent with film thic knesses in that samples exhibiting Type I spherulites were films of th ickness > 50 mu m, whereas Type II spherulites were grown in films of thickness of similar to 10 mu m. The differences in the growth rate an d morphology between the Type I and Type II spherulites have, thus, be en attributed to differences in film sample thickness; the causes behi nd such effects, however, still remain unclear.