Equilibration of linear polyethylene melts with pre-defined molecular weight distributions employing united atom Monte Carlo simulations.

The article focuses on the development of a new, computationally efficient Metropolis acceptance criterion for connectivity-altering Monte Carlo (CAMC) simulations that enables precise equilibration of polymer melts with any prescribed molecular weight distribution (MWD), including arbitrary and tabulated forms. Implemented on united-atom models of long-chain linear polyethylene (PE) melts, the method successfully equilibrates systems with various MWDs such as truncated most probable, Schulz–Zimm, Gaussian, bimodal Gaussian, and complex arbitrary distributions. Results indicate that while density and chain stiffness (Flory's characteristic ratio) are largely insensitive to MWD, the mixing behavior of chains, particularly in bimodal distributions, exhibits negative deviations from ideal solution behavior consistent with Flory–Huggins theory. This approach offers a versatile tool for simulating realistic polymer systems with controlled polydispersity, facilitating improved understanding and prediction of polymer properties relevant to industrial applications.