Characterization of Pressure Effects on the Cohesive Properties and Structure of Hexane and Polyethylene Using Molecular Dynamics Simulations

Molecular dynamics (MD) simulations using the OPLS-AA force field are conducted to compute pressure- and molecular-weight-dependence of Hildebrand's solubility parameters of hexane and high-density polyethylene (HDPE) at high pressures. The pressure dependence investigation also captures density data computed at high temperature and for external pressures ranging from 100 to 3000 bar. The effect of electrostatic potential energy contribution to cohesive energy and density is investigated and it is shown that the solubility parameter increases monotonically with increasing external pressure for both molecular mechanical models with and without electrostatic terms. Analysis of the pair distribution function is carried out versus pressure together with the influence of electrostatic energy contribution reflecting structural change of the condensed phase.