Simulation of polyethylene thin films composed of various chain lengths

Polyethylene thin films are simulated using a coarse-grained on-lattice Monte Carlo technique. Properties of free-standing films, which are made up of either C50, C100 or C316 chains, are analyzed in the melt phase at 509 K. As a result of increasing molecular weight, the following observations are made: (i) bulk density of the films increases; (ii) there is a higher degree of parallel orientation of bonds at the surface and a broader region over which this orientation survives; (iii) the decrease in the radius of gyration of the chains at the surface becomes more significant and (iv) parallel orientation of the chains at the surface is enhanced. Moreover, mixed films that contain both C50 and C100 chains are simulated. In these mixed films, the properties of C100 chains do not change, whereas the orientation of C50 chains and bonds is higher in the presence of longer chains.