分子动力学模拟预测壳聚糖的玻璃化转变温度

为了预测壳聚糖的玻璃化转变温度，在COMPASS力场和恒温恒压（NPT）系综条件下，利用分子动力学模拟方法，在343～543 K温度范围内研究了壳聚糖的玻璃化转变行为，通过模拟体系在不同温度下的比体积、回转半径和能量参数，获得了壳聚糖的玻璃化转变温度(T_g)。研究结果表明,壳聚糖的比体积、回转半径、内能随温度有规律的变化并在T_g处发生转折。模拟计算得到的壳聚糖的T_g与实验方法获得的值基本相符，分子动力学方法可用于壳聚糖玻璃化转变温度的预测。其中，通过回转半径-温度曲线获得的T_g与实验值最相符，回转半径是影响玻璃化转变的一个重要因素，可用于预测聚合物的玻璃化转变温度。

Prediction of glass transition temperature of chitosan through molecular dynamics simulation

The glass transition behavior of chitosan was studied through molecular dynamics (MD)simulation with the range of temperatures from 343 K to 543 K, and the glass transition temperature T_g of chitosan was obtained.The molecular mechanics force field used in this study was COMPASS(condensed-phase optimized molecular potentials for atomistic simulation studies)which has been validated for chitosan in some previous communications.Under the COMPASS force field and in the NPT ensemble, the specific volumes, radii of gyration and energies of chitosan at different temperatures were calculated.The results showed that the specific volume, radius of gyration and internal energy of chitosan regularly changed along with the change of temperature, and the transition began at the T_g point.The calculated T_g, especially the value obtained from the slop transition of the radius of gyration vs temperature curve, was in good agreement with the experimental results.Therefore, the radius of gyration has great influence on glass transition, and the MD simulation method is a useful tool to predict the glass transition temperature of polymer.