Statistical Analysis and Simulation of Pentad Distributions of Stereoblock Polypropylenes

Abstract

A method for simulating the microstructure of atactic−isotactic stereoblock polypropylene is presented. This method uses a computer program to generate stereosequences based on alternating blocks of isotactic and atactic stereosequences. Trends in observable stereochemical pentad distributions are examined, revealing that the pentad distributions become invariant above block lengths of 50 monomer units. These simulations reveal that two polymers with identical observable isotactic pentad distributions may have very different microstructures and thus different physical properties. The spectrum of an actual polymer is compared to the simulations, and it is revealed that many possible block lengths give reasonable fits but that similar values for weight fractions are obtained for each fit.