Cooperative Dynamics in Polymer Fluids: Melts, Blends, and their Glass Transition

该补助金支持理论研究的发展，一个严格的微观方法来描述结构均匀的聚合物动力学，但动态异质聚合物熔体和共混物作为其化学结构和热力学条件的函数。 在分子水平上理解聚合物熔体和共混物的性质对于新材料的开发具有重要意义。 这项研究是在过去几年中开发的原始方法的延伸，其中方程被形式化，并研究了未缠结聚合物熔体的动力学。 这是第一次，我们能够定量地描述在计算机模拟和实验中观察到的异常动力学的发病未纠缠聚乙烯动力学。 对于新的研究，我们专注于扩展我们的方法来描述聚合物熔体、过冷聚合物熔体和聚合物共混物中动态非均相流体的运动。 动力学不均匀性的存在下，随着温度的降低而增加的大小，似乎是负责的玻璃化转变的发病机制。 对非均相动力学和浓度波动之间相互作用的研究有可能解释结构均相聚合物共混物中存在的动力学异常现象，例如时间-温度叠加的破坏。这项资助支持了对聚合物系统动态响应的理论研究。 发展的理论将填补这些材料描述中的一个重要空白，应该有广泛的应用。

This grant supports theoretical research for the development of a rigorous microscopic approach to describe polymer dynamics in structurally homogeneous, but dynamically heterogeneous polymer melts and blends as a function of their chemical structure and of the thermodynamic conditions. The achievement of a molecular level understanding of the properties of polymer melts and blends is relevant for the development of new materials. This research is an extension of the original approach developed over the past few years of the prior grant, where the equations were formalized and the dynamics of unentangled polymer melts were investigated. For the first time, we were able to describe quantitatively the onset of anomalous dynamics observed in computer simulations and experiments of unentangled polyethylene dynamics. For the new research we focus on extending our approach to describe the motion of dynamically heterogeneous fluids in polymer melts, undercooled polymer melts and polymer blends. The presence of dynamical heterogeneities, increasing in size with decreasing temperature, appears to be the mechanism responsible for the onset of the glass transition. A study of the interplay between heterogeneous dynamics and concentration fluctuations is likely to explain the dynamical anomalies present in structurally homogeneous polymer blends, such as the breaking of time-temperature superposition.%%% This grant supports a theoretical investigation of the dynamical response of polymer systems. The theory developed will fill an important gap in the desciption of these materials and should have wide application.***