摘要
By this Monte Carlo simulation we studied the glass transition of polymethylene using the modified bond-fluctuation model combined with considering the rotational-isomeric state model. The configurational properties in the polymethylene (PM) melts, such as the mean length, the mean energy per bond and the mean square radius of gyration were monitored. We found that the chains cannot be in the equilibrium states after a very long time when the temperature of the dense PM chains decreases to 120 K. As the melt vitrifies, these quantities gradually become independent of temperature in a narrow range. The glass transition temperature T-g depends upon the chain length of PM chains, and extrapolation to (CH2)(infinity) gives T-g(infinity) = 212 K. The dynamics in the PM melts was also studied. It was found that the diffusion coefficients can be described by the Vogel-Fulcher law and the Vogel-Fulcher temperature T-0 is 124 K. This method may be used to investigate the glass transition of other real polymer chains.
By this Monte Carlo simulation we studied the glass transition of polymethylene using the modified bond-fluctuation model combined with considering the rotational-isomeric state model. The configurational properties in the polymethylene (PM) melts, such as the mean length, the mean energy per bond and the mean square radius of gyration were monitored. We found that the chains cannot be in the equilibrium states after a very long time when the temperature of the dense PM chains decreases to 120 K. As the melt vitrifies, these quantities gradually become independent of temperature in a narrow range. The glass transition temperature T-g depends upon the chain length of PM chains, and extrapolation to (CH2)(infinity) gives T-g(infinity) = 212 K. The dynamics in the PM melts was also studied. It was found that the diffusion coefficients can be described by the Vogel-Fulcher law and the Vogel-Fulcher temperature T-0 is 124 K. This method may be used to investigate the glass transition of other real polymer chains.
基金
This work was supported by National Natural Science Foundation of China (No. 29874012) and the National Key Projects for Fundamental Research "Macromolecules Condensed State" from STCC.
