Understanding Olefin Solubility in Polyethylene from a Molecular Dynamics Simulation Perspective

We investigated the sorption mechanisms of ethylene (ETH) and 1-hexene (HEX) in polyethylene (PE) using molecular dynamics (MD) simulations at 80 °C and various pressures. The simulations revealed that ETH molecules can hinder HEX-PE interactions, reducing HEX clustering with PE chains. This may explain the experimentally observed antisolvent effect of ETH on HEX. Conversely, HEX can enhance the sorption of ETH by acting as carriers, facilitating ETH interactions with PE chain ends. This cosolubility effect was captured by introducing a correction term, S_indirect, which accounts for ETH molecules that interact indirectly with PE via HEX. Total ETH solubility is thus expressed as S_ETH = S_direct + γS_indirect, where S_direct corresponds to ETH directly interacting with PE and γ represents the contribution from ETH molecules interacting simultaneously with HEX and PE. Our findings demonstrate that MD offer powerful insights into the molecular-level mechanisms governing sorption in complex, multicomponent systems, such as those encountered in polyolefin reactors.