Atomistic Monte Carlo simulation and continuum mean field theory of the structure and equation of state properties of alkane and polymer melts

Abstract

A continuum mean field approach based on Generalized Flory Theory and the Polymer Reference Interaction Site Model is developed to describe the structural and equation of state properties of normal alkane liquids and linear polyethylene melts. Efficient Monte Carlo simulations based on a new algorithm that employs concerted rotations around up to seven consecutive skeletal bonds along a chain are also conducted on the same systems. A realistic united-atom model is chosen to describe the geometry and energetics of the molecules and used throughout the study. Comparisons between the simulations and experimental thermodynamic and structural results are good and those between the mean field theory and the exact simulation results are reasonable. A method is described for quickly sampling the conformation of unperturbed chains in continuous space. The statistics of these chains compare very well with conformationally equilibrated chain statistics from the bulk simulation; this provides a confirmation of Flory's Random Coil Hypothesis. The need for improving the mean field theory and for enhancing the equilibration rate of the Monte Carlo simulations are identified. A new neighbor-list scheme is introduced for use in polymer Monte Carlo simulations.