A MONTE CARLO STUDY OF THE GLASS TRANSITION OF POLYMETHYLENE

摘要

By this Monte Carlo simulation we studied the glass transition of polymethylene using themodified bond-fluctuation model combined with considering the rotational-isomeric state model. Theconfigurational properties in the polymethylene （PM） melts, such as the mean length, the mean energy perbond and the mean square radius of gyration were monitored. We found that the chains cannot be in theequilibrium states after a very long time when the temperature of the dense PM chains decreases to 120 K. Asthe melt vitrifies, these quantities gradually become independent of temperature in a narrow range. The glasstransition temperature Tg depends upon the chain length of PM chains, and extrapolation to （CH2）∞givesTg∞=212 K. The dynamics in the PM melts was also studied. It was found that the diffusion coefficients canbe described by the Vogel-Fulcher law and the Vogel-Fulcher temperature T0 is 124 K. This method may beused to investigate the glass transition of other real polymer chains.