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

提出的研究涉及聚合物分子耦合过程的研究。过去有两种方法来描述聚合物分子的热力学。一种方法是将整个分子视为一个单一的组成部分，尽管单个聚合物分子可能由10,000个链原子组成，其中每个链原子都有一定的独立迁移率。另一种方法是将每个链原子视为一个独立的组成部分，尽管事实上所有链原子都是连接在一起的。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解耦的可能性。局部解耦限制了可以作为独立组件处理的链段。时间解耦限制了过程中的连续步骤，这些步骤发生得太慢，无法由单个分子驱动力作用，这在缓慢作用的聚合物中很常见。近十年来，调温量热法发展到可以定量区分可逆和不可逆过程的程度。用这种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（如熔化和结晶）的时间和位置效应，然后可以将其与上述解耦联系起来。发现不同组分长度的多相亚稳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共聚物的特征是微相和纳米相的全局亚稳态系统，由于聚合物分子比相尺寸长，并且通过中间解耦成为多个相的一部分，因此具有跨其边界的强连接。包括结晶、有序、取向、熔化、无序、混合、玻璃化和反玻璃化在内的状态变化将被研究。拟议的研究的智力价值将是增加对聚合物的理解，这是科学的一部分，目前有一半以上的科学家参与其中。更广泛的影响包括，一旦在纤维、薄膜、塑料等领域（包括蛋白质和淀粉等生物聚合物）中建立了结构、性能和加工之间的联系，在应用于聚合物材料时，减少了对试验和错误的需求。所提出的定量热力学分析的基础是先进的热分析系统（ATHAS），它是在过去30年里在NSF的支持下开发的。广泛的教学工作从科学出版物，讨论，讲座，到学生和博士后助理的指导，都达到了国际水平。计算机课程可以在互联网上学习新的结果。在过去的5年里，一个先前的国家科学基金会资助数据库和计算机课程的持续时间被超过25000名访问者访问。

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.