Correlated Many-Chain Dynamics: Slow Modes, Entanglements, and Glass Transition.

9971687 Guenza理解聚合物材料的技术和生物学特性的关键是要有一个强大的理论方法，能够在分子结构和实验数据之间建立联系。在分子水平上理解聚合物体系的宏观性质对于成功合成具有特定性质的新材料至关重要。一些严谨的理论方法已经被开发出来，成功地描述了基于微观物理图像的实验结果。然而，由于聚合物流体中重要运动的时间和空间尺度的范围是如此广泛（从5秒到几天，几年甚至更长），过去已经开发了针对每种物理现象的不同方法。对于一些重要的现象，还没有形成理论，例如过冷聚合物系统的动力学。为了对聚合物的物理性质进行一致的处理，我们需要有一种理论，能够以统一的方式描述不同环境下的聚合物系统：在不同的温度下（从熔体到玻璃化转变），不同的聚合物体积分数（从单分子溶液到熔体），不同的结构（线性，星形，树突状），以及不同的局部聚合物灵活性（蛋白质，DNA，聚合物液晶）。虽然统一理论的重要性在原则上一直是明确的，但直到现在才有可能实现这一目标。提出了一种新的理论方法，并应用于聚合物体系动力学的统一图景。关键的因素是在动力学方程中不仅描述分子内，而且描述分子间相互作用项的贡献。对于弱分子间相互作用，该理论恢复了具有记忆函数的Rouse理论所描述的单链动力学，即广义朗之万方程。增加了分子间相互作用的强度，该理论描述了聚合物液体的许多链特征的同时动力学。对于非常强的分子间相互作用，反常指数出现在聚合物扩散和时间相关函数中。有趣的是，电位的强度可以通过不同的方式增强：通过增加聚合物的分子量，通过增加聚合物的体积分数，或通过降低系统的温度。同样的方程描述了出现在纠缠聚合物流体、过冷聚合物系统和高密度聚合物流体中的异常动力学。要了解高分子材料的技术和生物学特性，关键是要有一个强有力的理论方法，能够把分子结构和实验数据联系起来。在分子水平上理解聚合物体系的宏观性质对于成功合成具有特定性质的新材料至关重要。一些严谨的理论方法已经被开发出来，成功地描述了基于微观物理图像的实验结果。然而，由于聚合物流体中重要运动的时间和空间尺度的范围是如此广泛（从5秒到几天，几年甚至更长），过去已经开发了针对每种物理现象的不同方法。对于一些重要的现象，理论尚未发展，如在过冷聚合物系统动力学的情况下，这项资助将发展一个新的理论，为聚合物中的各种现象提供一个统一的方法。除了增加我们对这些系统的基本理解外，这项工作还将具有技术应用。

9971687 Guenza A key to understanding the technological and biological properties of polymeric materials is to have a powerful theoretical approach that is capable of making the connection between molecular structure and experimental data. A molecular level understanding of the macroscopic properties of polymeric systems is essential for a successful tailored synthesis of new materials with specific properties. Several rigorous theoretical approaches have been developed that successfully describe the experimental findings on the basis of a microscopic physical picture. However, since the range of temporal and spatial scales of the important motions in polymeric fluids is so broad (from psec to days, years or even longer), in the past different approaches have been developed that are specific for each physical phenomenon. For some important phenomena, a theory has not yet been developed, as in the case of the dynamics of supercooled polymer systems.To have a consistent treatment of the physics of polymers we need to have a theory that can describe, in a unified way, polymer systems in different environments: at different temperatures (from the melt to the glass transition), different polymer volume fractions (from single molecule solution to melt), different architectures (linear, star, dendrimers), and different local polymer flexibilities (protein, DNA, polymer liquid srystals). While the importance of a unified theory has always been clear in principle, it has never been possible to achieve this goal until now.A new theoretical approach is developed and applied for a unified picture of the dynamics of polymeric systems. The key ingredient is the presence of contributions describing not only the intramolecular, but also the intermolecular interaction terms in the dynamic equations. For weak intermolecular interactions, the theory recovers the single chain dynamics as described by the Rouse theory with memory function, i.e., the generalized Langevin equation. Increasing the strength of the intermolecular interactions, the theory describes the simultaneous dynamics of many chains characteristic of a polymeric liquid. For very strong intermolecular interactions anomalous exponents appear in the polymer diffusion and time correlation functions. Interestingly, the strength of the potential can be enhanced in different ways: by increasing the molecular weight of the polymer, by increasing the polymer volume fraction, or by decreasing the temperature of the system. The same equations describe the anomalous dynamics that appear in entangled polymer fluids, supercooled polymer systems, and highly dense polymer fluids.%%%A key to understanding the technological and biological properties of polymeric materials is to have a powerful theoretical approach that is capable of making the connection between molecular structure and experimental data. A molecular level understanding of the macroscopic properties of polymeric systems is essential for a successful tailored synthesis of new materials with specific properties. Several rigorous theoretical approaches have been developed that successfully describe the experimental findings on the basis of a microscopic physical picture. However, since the range of temporal and spatial scales of the important motions in polymeric fluids is so broad (from psec to days, years or even longer), in the past different approaches have been developed that are specific for each physical phenomenon. For some important phenomena, a theory has not yet been developed, as in the case of the dynamics of supercooled polymer systemsIn this grant a new theory will be developed which provides a unified approach to diverse phenomena in polymers. Besides increasing our fundamental understanding of these systems, this work will also have technological applications.