从动力学和材料性能对摩擦参数进行比较,用于粗粒聚合物化物
Lilian C Johnson1, Frederick R Phelan1
1Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
The journal of physical chemistry. B
|July 31, 2023
概括
本研究通过比较来自扩散和粘度测量的摩擦参数来验证粗粒 (CG) 聚合物模型. 对于素和短聚烯链的一致结果表明,扩散摩擦参数化可靠地模拟粘度.
科学领域:
- 计算材料科学 计算材料科学
- 聚合物物理 聚合物物理
- 统计力学就是统计力学.
背景情况:
- 粗粒度 (CG) 模型简化了复杂的分子系统,以实现高效的模拟.
- 代博尔兹曼倒置 (IBI) 和兰格温恒温器是CG模型参数化的关键.
- 在多个时间尺度上准确地捕捉聚合物动态仍然是一个挑战.
研究的目的:
- 通过使用扩散度和材料特性 (粘度) 来参数化动力学来扩展CG建模.
- 评估不同方法 (扩散与粘度) 衍生的摩擦因子的一致性.
- 调查温度和链条长度对CG模型动态的影响.
主要方法:
- 使用代博尔兹曼逆转 (IBI) 的保守潜力的参数化.
- 使用可调节摩擦的消散式朗格温恒温器对加速动态进行校正.
- 通过Green-Kubo (GK) 方法测量零剪切粘度.
- 扩散测量 (比秒到纳秒) 的分析和与粘度衍生摩擦的比较.
主要成果:
- 对于方,摩擦和粘度显示一致的阿雷尼乌斯式温度依赖.
- 短聚烯链在扩散和粘度方法中表现出一致的摩擦.
- 较长的聚乙烯链显示了摩擦的差异,取决于测量方法 (旋转,转移或粘度).
- 时间依赖的摩擦是必要的,以捕捉所有时间尺度上的动态,特别是在子过渡期间.
结论:
- 扩散摩擦参数化是一种可靠且具有成本效益的方法,用于模拟高温聚合物融中的粘度.
- 较长链的摩擦差异凸显了测量方法对系统放松时间的敏感性.
- 可能需要非马科夫的方法来恢复所有原子 (AA) 动态在更广泛的时间尺度.
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