Comparison of ring and linear polyethylene from molecular dynamics simulations

A molecular dynamics simulation was performed to investigate ring and linear polyethylene molecules. A confirmed atomistic force field of polyethylene was applied in a constant temperature and constant pressure simulation algorithm. A united model was used to study the methylene and methyl groups. To measure the average size of polymer, mean square radius of gyration was used. It was found that topological constraints lead to more compact structures for the rings than the linear molecules. The value νl for linear polyethylenes exceeded the value for an ideal freely jointed linear chain in a polar solvent. The Brownian dynamics (BD) simulations of rings showed the shrinkage of the ring polymers in a melt as compared with the unperturbed chains. The local conformational properties were investigated by comparing the static structure factors represented by Kratky plots. It was found that the rings collapsed in a melt by comparing their radii of gyration with those of phantom chains.