Recent results on the polymorphic behavior of isotactic polypropylene

The more recent results concerning the polymorphic behavior of isotactic polypropylene (iPP) are presented. Specifically contributions on the recently determined γ phase crystal structure, in which non-parallel chains coexist, and the novel results concerning the β phase are summarized. The new data appear to suggest that the normally occurring α-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 questions arising from the new findings with respect to morphology and polymer crystal growth are considered.