Investigation of Atomistic Simulation of Structural and Dynamic Differences in Glassy and Liquid States of Atactic Poly(Propylene).

摘要

Atomistic simulation techniques, in conjunction with experimental and theoretical approaches, have proven themselves to be useful tools for the study of materials. Recent years have seen the first application of a variety of simulation methods to investigating the phenomena occurring in bulk polymers. Among these, possibly the most important and challenging is the glass transition. Despite its significance, the glass transition is still poorly characterized except in a phenomenological manner. For instance, comprehension of how the structure of a polymer glass differs from that of the liquid is limited to the somewhat vaguely defined concept of free volume. It is not known how the volume associated with atoms might be distributed within the polymer or how changes in the distribution are related to the property changes seen at the glass transition. In addition, what other structural changes occur on passing between the liquid and glass states are not known. These questions involve the local atomic level structure and motion of individual or small groups of atoms. Available experimental and theoretical methods are not well suited to investigate these details. Therefore, simulation is the only way to obtain physical insight into these problems at the present time. Reported here are initial results obtained from a series of such computer simulations carried out on a simple vinyl polymer, atactic poly(propylene). Keywords: Computer simulation; Structural relaxations in glassy polymers; Glass transition; Molecular structure; Molecular interactions; Transition phases. (KT)