RECENT RESULTS ON THE POLYMORPHIC BEHAVIOR OF ISOTACTIC POLYPROPYLENE

The more recent results concerning the polymorphic behavior of isotact ic polypropylene (iPP) are presented. Specifically contributions on th e recently determined gamma phase crystal structure, in which non-para llel chains coexist, and the novel results concerning the beta phase a re summarized. The new data appear to suggest that the normally occurr ing alpha-phase is in general neither the kinetically favored nor the thermodynamically more stable phase but rather it represents the best compromise between these two criteria. The implications and the open q uestions arising from the new findings with respect to morphology and polymer crystal growth are considered.