Seminar Abstract:
The solid state properties of many technologically important polymers are exquisitely sensitive to the molecular structure and chain-like nature of the molecules and to the organization of these chains into a “semicrystalline” morphology. These features reflect both the kinetic nature of crystallization and the metastable thermodynamics of the resulting crystal/amorphous polymer composite morphology, topics that have been the subject of debate within the polymer community for decades. Recent experimental, theoretical and simulation studies are generating new ideas that call for a re-examination of these old debates. Furthermore, crystallization kinetics and structure/property relations in nanocomposites are both areas of fundamental scientific interest, with ramifications that transcend the realm of crystallizable polymers. The modeling of polymer crystallization and of the semicrystalline solid state with chemical level detail still poses significant challenges for molecular simulation, however, due to the nonequilibrium nature of the structures involved and the broad spectrum of time scales implicated in structural reorganization. In this talk, I describe progress in the development of molecular simulations to illuminate these phenomena. Crystallization kinetics are examined for both the nucleation and growth of crystallites, taking advantage of molecular dynamic and Monte Carlo techniques to study rare event dynamics. Then, an atomically detailed model for the semicrystalline morphology is proposed and its properties examined, with particular emphasis on understanding the mechanical response of semicrystalline polyolefins.