Coupling Within and Between Nanophases of the Global, Metastable Structure of Polymers

这项拟议的研究涉及对聚合物中分子耦合过程的研究。在过去，有两种方法来描述聚合物分子的热力学。一种是将整个分子视为单一成分，尽管一个聚合物分子可能由10,000个链原子组成，每个原子都有一定的独立迁移率。另一种是将每个链原子视为一个独立的组成部分，尽管所有的链原子都是链接在一起的。这两种描述都不适用于所有情况。新的想法是测试识别局部或时间脱钩的可能性。局部分离限制了可被视为独立组件的链段。时间解耦限制了过程中的连续步骤，这些步骤发生得太慢，不能受到单个分子驱动力的作用，这是慢作用聚合物中常见的现象。在过去的十年里，温度调制量热法发展到了能够定量区分可逆和不可逆过程的程度。用这项技术研究了温度变化的频率和幅度变化的影响，并允许找到可逆和不可逆过程的时间和位置效应，如熔化和结晶，然后可以与上述去耦合联系起来。不同组分长度的多相、亚稳态结构经历了不同程度的可逆性转变，半晶材料和不相容嵌段的共聚物被表征为微米相和纳米相的整体亚稳体系，由于聚合物分子长于相尺寸并以中间解偶方式成为多相的一部分，因此具有跨边界的强连接。涉及结晶、有序、取向、熔化、无序、混合、玻璃化和非玻璃化的状态变化将被研究。拟议研究的智力价值将是增加对聚合物的理解，这是目前涉及所有科学家的一半以上的科学的一部分。更广泛的影响包括，一旦在纤维、薄膜、塑料等领域以及包括蛋白质和淀粉等生物聚合物领域建立了结构、性能和加工之间的联系，就减少了在聚合物材料应用中的反复试验的需要。提出的定量热力学分析的基础是高级热分析系统(ATAS)，该系统是在美国国家科学基金会的支持下在过去30年中开发的。广泛的教学工作包括科学出版物、讨论和讲座，以及对学生和博士后助理的指导，所有这些都是在国际层面上进行的。在互联网上有一门计算机课程可以学习新的结果。在过去的5年里，超过25,000名参观者访问了之前的NSF授予的数据库和计算机课程。

The proposed research involves a study of molecularly coupled processes in polymers. In the past there were two ways to describe polymer molecules thermodynamically. One was to treat the whole molecule as a single component, despite the fact that a single polymer molecule may consist of 10,000 chain atoms of which each has a certain amount of independent mobility. The other was to treat each of the chain atoms as an independent component, despite the fact that all chain atoms are linked together. Neither description works for all situations. The new idea is to test the possibility to identify local or temporal decoupling. The local decoupling limits the chain segments that can be treated as an independent component. The temporal decoupling limits successive steps in a process which occur too slowly to be acted upon by a single molecular driving force, a common occurrence in slowly acting polymers.In the last ten years, temperature-modulated calorimetry was developed to a degree to be able to quantitatively distinguish reversible and irreversible processes. The effect of frequency- and amplitude-variation of temperature-changes is studied with this technique and allows to find the time- and position-effect of reversible and irreversible processes such as melting and crystallization, which can then be linked to the decoupling described above. Multi-phase, metastable structures of different component length were found to undergo transitions of different degrees of reversibility.Semicrystalline materials and copolymers of incompatible blocks are characterized as globally metastable systems of micro- and nanophases with strong connections across their boundaries due to polymer molecules that are longer than the phase dimensions and become part of more than one phase with intermediate decoupling. Changes of state involving crystallization, ordering, orienting, melting, disordering, mixing, vitrification, and devitrification are to be studied.The intellectual merit of the proposed research would be an increased understanding of polymers, a part of science which presently involves more than half of all scientists. The broader impact involves a reduction of the need for trial and error in the application to polymeric materials as soon as the connection between structure, properties, and processing is established in areas such as fibers, films, plastics, etc. and including also biological polymers such as proteins and starches. The basis of the quantitative, thermodynamic analyses proposed is the Advanced THermal Analysis System (ATHAS), developed over the last 30 years with NSF support. Extensive teaching efforts reach from scientific publications, discussions, and lectures, to instruction of students and postdoctoral associates, all on an international level. A computer course is available over the internet for study of the new results. Over the last 5 years, the duration of a prior NSF Grant the Data Bank and Computer Course were accessed by more than 25,000 visitors.