Local Polymer Dynamics in Solutions, Melts, Blends, and Glasses

给定链的局部节段动力学是由化学结构、分子内势和链的环境决定的。光学实验，核磁共振实验和分子动力学计算机模拟将进行研究这些方面的局部动力学在聚合物溶液，熔体，混合物，和玻璃。一个项目将利用分子动力学计算机模拟来研究Tg是否与响应构象转变时发生的协同运动的程度有关。模拟是了解局部聚合物运动的微观特征的理想工具，当它们通过实验进行测试时，可以评估真实感。第二个项目将使用最近开发的光漂白技术来探索物理老化的分子起源。随着时间的推移，物理老化会导致玻璃状聚合物的性能退化。这些实验也将有助于揭示聚合物玻璃化转变的基本性质。第三个项目将使用低场核磁共振光谱来研究聚合物混合物的两种成分如何影响彼此的局部动力学。这些影响决定了共混物的机械性能。最终，从组分性质来预测共混物的性质可能是可行的。局部聚合物动力学在非晶聚合物的结构/性能关系中起着重要的作用。局部动力学直接决定了许多重要的聚合物性质，如玻璃化转变温度和粘度的温度依赖性。对局部聚合物动力学的基本理解可能允许对现有材料进行改性以增强特定性能，并可能开发新材料。* * *

9424472 Ediger The local segmental dynamics of a given chain are determined by chemical structure, intramolecular potentials, and the chain's environment. Optical experiments, NMR experiments, and molecular dynamics computer simulations will be performed to investigate these aspects of local dynamics in polymer solutions, melts, blends, and glasses. One project will utilize molecular dynamics computer simulations to investigate whether Tg is related to the extent of cooperative motion which occurs in response to a conformational transition. Simulations are an ideal tool to understand the microscopic features of local polymer motion when they are tested by experiments which allow an assessment of realism. A second project will use a recently developed photobleaching technique to explore the molecular origins of physical aging. Physical aging causes degradation of the properties of glassy polymers over time. These experiments will also help to unravel the fundamental nature of the glass transition in polymers. A third project will use low-field NMR spectroscopy to study how the two components of a polymer blend influence each other's local dynamics. These influences determine the mechanical properties of the blend. Ultimately, a prediction of blend properties from component properties may be feasible. %%% Local polymer dynamics play an important role in the structure/property relationships of amorphous polymers. Local dynamics are directly responsible for a number of important polymer properties such as the glass transition temperature and the temperature dependence of the viscosity. A fundamental understanding of local polymer dynamics may allow the modification of existing materials to enhance specific properties and possibly the development of new materials. ***