Chremos Alexandros, Douglas Jack F
Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Polymers (Basel). 2019 Jun 14;11(6):1045. doi: 10.3390/polym11061045.
We probe the influence of branching on the configurational, packing, and density correlation function properties of polymer melts of linear and star polymers, with emphasis on molecular masses larger than the entanglement molecular mass of linear chains. In particular, we calculate the conformational properties of these polymers, such as the hydrodynamic radius R h , packing length , pair correlation function g ( r ) , and polymer center of mass self-diffusion coefficient, , with the use of coarse-grained molecular dynamics simulations. Our simulation results reproduce the phenomenology of simulated linear and branched polymers, and we attempt to understand our observations based on a combination of hydrodynamic and thermodynamic modeling. We introduce a model of "entanglement" phenomenon in high molecular mass polymers that assumes polymers can viewed in a coarse-grained sense as "soft" particles and, correspondingly, we model the emergence of heterogeneous dynamics in polymeric glass-forming liquids to occur in a fashion similar to glass-forming liquids in which the molecules have soft repulsive interactions. Based on this novel perspective of polymer melt dynamics, we propose a functional form for that can describe our simulation results for both star and linear polymers, covering both the unentangled to entangled polymer melt regimes.
我们探究了支化对线性和星形聚合物熔体的构型、堆积以及密度相关函数性质的影响，重点关注分子质量大于线性链缠结分子质量的情况。特别地，我们使用粗粒化分子动力学模拟计算了这些聚合物的构象性质，如流体力学半径(R_h)、堆积长度、对相关函数(g(r))以及聚合物质心自扩散系数。我们的模拟结果再现了模拟线性和支化聚合物的现象学，并且我们尝试基于流体力学和热力学建模的结合来理解我们的观察结果。我们引入了一种高分子质量聚合物中“缠结”现象的模型，该模型假设聚合物在粗粒化意义上可被视为“软”粒子，相应地，我们对聚合玻璃形成液体中异质动力学的出现进行建模，其发生方式类似于分子具有软排斥相互作用的玻璃形成液体。基于聚合物熔体动力学的这一新视角，我们提出了一种(的函数形式，它可以描述我们对星形和线性聚合物的模拟结果，涵盖了从非缠结到缠结的聚合物熔体区域。
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