Monte Carlo Simulation of the Glass Transition in Polyethylene

The end-bridging (EB) Monte Carlo (MC) move has been used to simulate united atom models of bulk and end-grafted polyethylene both above and below the glass transition temperature (Tg). In previous work, EB move has been shown to lead to significant improvement in the relaxation of melts consisting of long polymer chains. We find that although a reasonable fraction of EB moves get accepted below glass transition in our MC simulation, the autocorrelation function of the chain end-to-end vector does not relax completely at these low temperatures. The temperature dependence of enthalpy and density is used to calculate the Tg for both bulk and thin film systems. For the film consisting of chains grafted on a hard surface, the Tg is slightly lower than that for the bulk, as expected in a system with unfavorable polymer-surface interactions.