Reorientational Dynamics and Intermolecular Cooperativity in Crosslinking Polymers

9710480米约维奇这项资助涉及对交联聚合物中偶极运动动力学的基础研究。玻璃形成材料的动力学目前在科学界是一个相当活跃的主题，但迄今为止还没有关于由于化学反应而经历结构时间演变的系统的动力学的全面研究报道。化学反应的进步改变了材料的本质，并为分子运动动力学的研究增加了一个新的维度。化学成分、物理特征和形态的变化伴随着节段性运动或松弛的时间尺度的连续变化。当一个信号(本研究中的电场)作用于聚合物时，多个分子链段必须一致响应。这需要分子水平上的合作，因此，基本的论点应该从这样一个命题开始，即弛豫过程受分子间协作性的支配。这项研究的主要目的是研究偶极动力学在交联过程中的变化，并利用这些结果：1)描述网络形成过程中各个阶段各种弛豫过程的分子起源；2)制定一种将网络的化学和物理状态与偶极动力学联系起来的方法；以及3)从分子间的协作性来解释网络动力学。%所提出的方法具有跨学科的性质，将使我们能够从根本上理解交联聚合物中的重定向动力学和分子间的协作性。预计这项研究完成后，将在分子水平上深入了解由于化学反应而经历结构时间演变的聚合物的重定向动力学。***

9710480 Mijovic This grant concerns a fundamental investigation of the dynamics of dipole motions in crosslinking polymers. Dynamics of glass-forming materials are currently a subject of considerable activity in the scientific community, but no comprehensive study has been reported hitherto on the dynamic of systems that undergo a temporal evolution of structure as a result of chemical reactions. The advancement of chemical reactions alters the very nature of the material and adds a new dimension to the study of dynamics of molecular motions. Changes in the chemical composition, physical characteristics and morphology are accompanied by a continuous variation in the time scale for segmental motions or relaxations. When a signal (electric field in this study) is applied to a polymer, a number of molecular segmental must respond in unison. That requires cooperation on the molecular level, and hence the fundamental argument should begin with the proposition that the relaxation processes are governed by intermolecular cooperativity. The principal objectives of the research are to investigate the changes in dipole dynamics during crosslinking and utilize the results to: 1) describe the molecular origin of various relaxation process at all stages during network formation; 2) formulate a methodology for relating the chemical and physical state of the network to dipole dynamics; and 3) provide an interpretation of network dynamics in terms of intermolecular cooperativity. %%% The proposed methodology is of an interdisciplinary nature and will permit a fundamental understanding of reorientational dynamics and intermolecular cooperativity in crosslinking polymers. It is expected that the research, when completed, will afford a molecular-level insight into the reorientational dynamics of polymers that undergo a temporal evolution of structure as a result of chemical reactions. ***