(5b) Molecular Simulation of Metastable and Semi-Crystalline Polymers

Monte Carlo simulations are employed to probe the temperature dependent properties of the intercrystalline region in isotactic polypropylene(iPP), in the first such detailed, molecular level study of a polymer with side groups. Polymer chains are represented by a united atom force-field model, while the simulation setup mimics the typical crystal-constrained amorphous microstructure of the alpha-2 phase of iPP. In conjunction with local MC moves that modify the topology and conformation of mobile polymer segments, parallel tempering in energy space is employed to achieve effective equilibration and sampling of phase space. The effect of temperature on the probability distributions of chain features associated with the interphase, as well as the decay in ordered sequential arrangement of backbone dihedrals across the fold surface is investigated. These results are compared with previous investigations of polyethylene and the contradistinction between prototypical linear and branched polymers will be presented.