Investigating structure and dynamics of unentangled poly(dimethyl- co -diphenyl)siloxane via molecular dynamics simulation
Investigating structure and dynamics of unentangled poly(dimethyl- co -diphenyl)siloxane via molecular dynamics simulation
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通过分子动力学模拟研究未缠结的聚（二甲基-共-二苯基）硅氧烷的结构和动力学
作者：
Xian, Weikang;He, Jinlong;Maiti, Amitesh;Saab, Andrew P.;Li, Ying
聚硅氧烷是一种重要的高分子材料。聚二甲基硅氧烷在低温下表现出玻璃状的机械性能。例如，通过共聚引入苯基硅氧烷，不仅改善了低温弹性，而且还提高了其在宽温度范围内的性能。与苯基组分的共聚可以显著改变聚硅氧烷的微观性质，例如链动力学和松弛。然而，尽管在文献中有很多工作，这种变化的影响仍然没有得到清楚的理解。本文采用原子分子动力学模拟方法，系统地研究了无规聚（二甲基-二苯基）硅氧烷的结构和动力学。随着联苯组分摩尔比的增加，我们发现线性共聚物链的尺寸扩大。同时，链扩散率减慢超过一个数量级。降低的扩散率似乎是一个复杂的相互作用的结果，由苯基取代引起的结构和动态变化。
Polysiloxane is one of the most important polymeric materials in technological use. Polydimethylsiloxane displays glass-like mechanical properties at low temperatures. Incorporation of phenyl siloxane, via copolymerization for example, improves not only the low-temperature elasticity but also enhances its performance over a wide range of temperatures. Copolymerization with the phenyl component can significantly change the microscopic properties of polysiloxanes, such as chain dynamics and relaxation. However, despite much work in the literature, the influence of such changes is still not clearly understood. In this work, we systematically study the structure and dynamics of random poly(dimethyl-co-diphenyl)siloxane via atomistic molecular dynamics simulations. As the molar ratio ϕ of the diphenyl component increases, we find that the size of the linear copolymer chain expands. At the same time, the chain-diffusivity slows down by over an order of magnitudes. The reduced diffusivity appears to be a result of a complex interplay between the structural and dynamic changes induced by phenyl substitution.