The Role of Stereoregularity in Polypropylene Melts: Insights from Coarse-Grained Simulations

The tacticity of vinyl polymers is a crucial factor governing their physical properties, such as chain conformation and stiffness. In this work, we apply the tacticity-preserving coarse-graining methodology established by Milano and Müller-Plathe to investigate isotactic, atactic, and syndiotactic polypropylene (PP) melts. Using structure-based coarse-grained (CG) models derived from all-atom molecular dynamics (MD) simulations, we employ the Iterative Boltzmann Inversion (IBI) method to develop thermodynamically consistent CG models that accurately capture the stereoregularity-dependent structural features of PP. Our simulation results reveal a significant influence of tacticity on chain rigidity, Flory's characteristic ratio, Kuhn length, and entanglement length, with findings in qualitative agreement with existing experimental and theoretical studies. We further establish quantitative relationships between chain conformation, entanglement, and dynamics in PP melts with varying stereoregularity. This study extends established CG methodologies to polypropylene─an industrially important polymer whose tacticity-dependent mesoscale properties have not been systematically explored using such models─and demonstrates the capability of tacticity-aware CG models in probing microstructure-property relationships in this widely used thermoplastic.