• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The Journal of Chemical Physics >Cooling rate dependence of the glass transition temperature of polymer melts: Molecular dynamics study
【24h】

Cooling rate dependence of the glass transition temperature of polymer melts: Molecular dynamics study

机译：聚合物熔体的玻璃化转变温度对冷却速率的依赖性：分子动力学研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

A coarse-grained bead spring model of short polymer chains is studied by constant pressure molecular dynamics (MD) simulations. Due to two competing length scales for the length of effective bonds and the energetically preferred distance between nonbonded beads, one observes a glass transition when dense melts are cooled down (as shown in previous work, at a pressure p = 1 the mode coupling critical temperature is at T_c approx = 0.45 and the Vogel-Fulcher temperature is T_0 approx = 0.33, in Lennard-Jones units). The present work extends these studies, estimating a cooling-rate-dependent glass transition temperature T_g(GAMMA) by cooling the model system from T = 0.6 down to T = 0.3, applying cooling rates from GAMMA approx = 10~(-3) to GAMMA approx = 10~(-6) (in MD time units), and attempting to identify T_g(GAMMA) from a kink in the volume versus temperature or potential energy versus temperature curves. It is found that T_g(GAMMA)lies in the range 0.43 <=T_g (GAMMA) <= 0.47, for the cooling rates quoted, and the variation of T_g(GAMMA) for GAMMA is compatible with the expected logarithmic variations. We will show why a detailed distinction between competing theories on these cooling rate effects would need an excessive amount of computer time. To estimate also the melting transition temperature T_m of this model, the sytem was prepared in a crystalline configuration as an initial state and heated up. The onset of diffusion, accompanied by an isotropization of the pressure tensor was observed for T_m approx = 0.77. This implies that the model is suitable for studying deeply supercooled melts.
机译：通过恒压分子动力学（MD）模拟研究了短聚合物链的粗粒珠弹簧模型。由于有效键合长度的两个相互竞争的长度标度以及非键合小珠之间的能量上优选的距离，人们观察到当致密的熔体冷却下来时，玻璃会发生转变（如先前的工作所示，在压力p = 1时，模式耦合临界温度）大约在T_c处= 0.45，Vogel-Fulcher温度在T_0大约= 0.33（以Lennard-Jones单位）。目前的工作扩展了这些研究，通过将模型系统从T = 0.6冷却到T = 0.3，并将GAMMA的冷却速率大约为10〜（-3）施加到玻璃，从而估算了与冷却速率相关的玻璃化转变温度T_g（GAMMA）。 GAMMA大约= 10〜（-6）（以MD时间单位），并尝试从体积对温度或势能对温度曲线的扭结中识别出T_g（GAMMA）。对于所引用的冷却速率，发现T_g（GAMMA）在0.43≤T_g（GAMMA）≤0.47的范围内，并且GAMMA的T_g（GAMMA）的变化与预期的对数变化兼容。我们将说明为什么在这些冷却速率影响的竞争理论之间进行详细区分会需要大量的计算机时间。为了也估计该模型的熔融转变温度T_m，将系统制备成初始状态的结晶构型并加热。对于T_m约＝ 0.77，观察到扩散的开始，伴随着压力张量的各向同性。这意味着该模型适用于研究过冷的熔体。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号