基于分子动力学方法研究间规聚丙烯温度相关性的热输运性质

Temperature dependent thermal transport of syndiotactic polypropylene by molecular dynamics simulations

建立了间规聚丙烯的分析模型,基于非平衡分子动力学方法研究了常规使用温度下间规聚丙烯的热输运性质。实验结果表明,聚合度为50的间规聚丙烯可用于构建热导率的分析模型,能反映间规聚丙烯的真实性质且计算量适中。随聚合度的增加,间规聚丙烯分子的第1个波谷深度的绝对值略有增加,声子振动态密度在低频段0~20 THz的强度有所减小,在高频段80~98 THz的波峰强度增强。当温度由270 K升至390 K时,间规聚丙烯的热导率由0.202 W/(m·K)增至0.241 W/(m·K),速度自相关函数的第1个波谷深度绝对值由0.449减小至0.368,0~40 THz处的低频分量逐渐减小,而40~48 THz处的高频声子群的数量有所增加。

An analytical model of syndiotactic polypropylene(s-PP) was established to reveal the thermal transport properties of s-PP at conventional operation temperatures based on classical nonequilibrium molecular dynamics simulations. The results show that s-PP with polymerization degree of 50 can be used to establish the thermal conductivity analytic model,which is an effective model to calculate the physical properties of s-PP with a moderate calculation amount. With the increase of polymerization degree,the absolute value for the first trough in the velocity autocorrelation function increases slightly,the intensity of the phonon vibrational density of state in frequency range of 0-20THz decreases,and the intensity of the phonon vibrational density of state in the frequency of 80-98 THz enhances. When the temperature rises from 270 K to 390 K,the thermal conductivity of s-PP increases from 0.201 W/(m·K) to 0.241 W/(m·K),the absolute value for the first trough in the velocity autocorrelation function decreases from 0.449 to 0.368,the phonon vibrational density of state of the low frequency component in 0-40 THz is suppressed,while the number of high frequency phonon groups in 40-48 THz is stimulated with increasing the temperature.