Nonequilibrium Molecular Characteristics of Glassy Polymers

简介：瞬态结构和性质的变化， 在化学和物理老化过程中发生在玻璃状聚合物中 和/或在低于玻璃化转变温度Tg下退火是优选的。 目前研究兴趣很大。 这种时间依赖性 行为，也称为体积或焓松弛（或 恢复），源于非平衡性质的 玻璃态 从应用的角度来看， 这种现象是预测未来的控制因素， “初始”行为以及玻璃的实际性能 或部分玻璃状的聚合物材料 一生 研究摘要：在这项研究中，PI探测的影响， 受控（和加速）化学和物理老化和/或 在可实现的阻隔性能水平上进行再生， 具有重要商业意义的玻璃态聚合物 （聚对苯二甲酸乙二醇酯）。 这将通过 在低于Tg的温度范围内调节聚合物 与小分子反渗透剂（在高化学势下） 其与小段区域交互。 最 重要的是，微观结构变化， 控制吸附中的传输参数的行为， 扩散将直接测量和识别的第一 时间，通过监测异构化的动力学 控制聚合物链段分布的反应 构象异构体 研究将通过结合 利用气体传输和傅立叶变换I.R. 光谱，连同焓松弛研究。 意义：这项工作的成果将大大有助于 发展了一个全面的分子理论， 导致各种新的和/或改进的工艺的设计 用于生产具有上级性能的玻璃态聚合物， 包装应用，作为保护涂层，以及用作 选择性渗透膜在高能效分离中的应用 气体混合物，仅举几个例子。 此外，知识 运输和机械性能的变化（这可以 通过自由体积及其分布相互关联） 在这项研究中获得。 预计新型聚合物 具有显著增强性能的微观结构状态 级别和应用程序生命周期将被发现。

Introduction: The transient structure and property changes that occur in glassy polymers during chemical and physical aging and/or annealing below the glass-transition temperature Tg are of great current research interest. This time-dependent behavior, also referred to as volume or enthalpy relaxation (or recovery), originates from the nonequilibrium nature of the glassy state. From an application point of view, it is apparent that this phenomenon is the controlling factor in predicting the "initial" behavior as well as the practical performance of glassy or partially glassy polymeric materials during their useful lifetimes. Research Summary: In this research, the PIs probe the effects of controlled (and accelerated) chemical and physical aging and/or rejuvenation on achievable barrier property levels in a carefully selected glassy polymer of major commercial significance (polyethylene terephthalate). This will be accomplished by conditioning the polymer over a range of temperatures below Tg with small molecule penetrants (at high chemical potentials) which are interactive with small segment regions. Most importantly, the microstructural changes which specifically control the behavior of transport parameters in sorption and diffusion will be directly measured and identified for the first time, via monitoring of the kinetics of the isomerization reaction which governs the distribution of polymer segmental conformers. The research will be accomplished through combined experiments utilizing gas transmission and Fourier Transform I.R. Spectroscopy, together with enthalpy relaxation studies. Significance: The results of this work will contribute strongly to the development of a comprehensive molecular theory which may lead to the design of a variety of new and/or improved processes for the production of glassy polymers with superior properties in packaging applications, as protective coatings, and for use as permselective membranes in energy-efficient separations of gaseous mixtures, to cite only a few examples. Also, knowledge of both transport and mechanical property variations (which can be interrelated through free volume and its distribution) will be acquired in this research. It is anticipated that novel polymer microstructural states with significantly enhanced property levels and application lifetimes will be discovered.