Reorientational Dynamics and Intermolecular Cooperativity in Crosslinking Polymers

[9710480] Mijovic这项资助涉及交联聚合物中偶极子运动动力学的基础研究。玻璃形成材料的动力学是目前科学界相当活跃的一个课题，但迄今为止还没有关于化学反应导致结构随时间演变的系统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、物理特性和形态的变化伴随着节段运动或弛豫的时间尺度的连续变化。当一个信号（本研究中的电场）被施加到聚合物上时，许多分子片段必须一致响应。这需要分子水平上的合作，因此基本论点应该从松弛过程由分子间合作控制的命题开始。本研究的主要目的是研究交联过程中偶极动力学的变化，并利用这些结果：1)描述网络形成各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；3)从分子间合作的角度解释网络动力学。所提出的方法是跨学科性质的，将允许对交联聚合物的重定向动力学和分子间协作性有一个基本的了解。预计这项研究完成后，将提供分子水平的洞察聚合物的重新定向动力学，这些聚合物由于化学反应而经历了结构的时间演变。＊＊＊

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. ***