Simulations on Thermoplastic Elastomers from Polypropylene

Abstract

Computer simulations have been carried out to investigate sequence lengths, and sequence-length distributions in stereoregular polymers. Simulations were also used to investigate the development of reinforcing crystallites in thermoplastic elastomers. New types of stereoblock polypropylene which have been prepared from some metallocene catalytsts and which function as thermoplastic elastomers through controlled crystallization are of particular interest in this regard. While it is widely believed that the sequence distributions in these polymers is of primary importance in their crystallization, no adequate theory is currently available. In the present investigation, the Windle approach with Monte Carlo methods was used to simulate one hundred copolymeric chains in order to search for crystallizable sequence matches in these polymers. Based on the amounts of crystallinity reported for these polymers at various feed compositions, estimates were made of melting points, interfacial free energies, standard free energies of fusion, and Young’s moduli at small extensions. The approach is also useful for predicting the sizes of the crystallites and the minimum sequence lengths required for crystallization.