Theory of polymer crystallization, melting, and interlude of metastability

非技术总结该奖项支持理论和计算研究，以及促进对聚合物结晶的理解的教育。非常长而细的链状巨大的高分子组成了这类材料，称为聚合物。这些材料通过服装、建筑材料、汽车和飞机零件等重新定义了我们的当代文明。聚合物材料所需的关键特征之一是能够从它们制造晶体，从而使它们可用作具有市场价值的最终产品。但是，这种大分子过程必定是一项不可能完成的任务，这一点可以通过考虑大量长而混杂的线而很容易地想象出来，这些线都缠结在一起。它们是如何整齐地排列成晶体的？事实上，分子确实形成晶体，至少部分。尽管这种部分有序的聚合物晶体在价值数十亿美元的聚合物工业中很普遍，但这种方法还没有被理解。对聚合物材料结晶过程的分子理解是材料领域长期存在的研究挑战之一。几十年来，在这个领域中，从现象学的角度收集了大量的谜题，需要一个理性的概念基础，这将有助于发现新的材料，以及理解已知的事实。该研究计划旨在开发基本概念，以了解聚合物如何结晶和熔融，使用理论和计算机建模。除了推进聚合物结晶领域外，拟议的活动还包括大力支持多样性和培训新一代研究生，使他们能够未来参与价值数十亿美元的半结晶聚合物行业。技术总结该奖项支持理论和计算研究以及教育，以促进对聚合物结晶的理解。聚合物溶液和熔体的结晶是高分子科学中一个长期的研究领域，具有巨大的工业价值。由于柔性大分子具有大量的构象，它们的结晶和熔融行为表现出广泛的令人困惑的现象学，这一直是难以理解的。这些难题出现在丰富的结构层次在多个长度尺度和时间尺度往往涉及长期存在的非平衡态。本研究计画旨在发展高分子结晶、熔融及介稳态阶层间的新理论。基于对半结晶聚合物中长寿命亚稳态和记忆效应的作用的新见解，拟议的研究将使用统计力学，场论和几种模拟技术进行。具体而言，PI计划解决：（i）结晶、熔化和记忆中的亚稳态间歇，（ii）层状堆叠的垂直结晶，（iii）自发选择和手性放大，以及（iv）层间非晶区域的不稳定性。该研究项目的结果预计将对聚合物加工等众多工业相关领域产生重大影响。今天的大多数材料都是由经过加工的半结晶聚合物制成的，这是拟议工作的重点。这些材料构成了一个价值数十亿美元的产业。对这类重要材料的基本了解将有助于设计和加工新型聚合物材料，从而为我们的社会带来更大的利益。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research, and education to advance understanding of polymer crystallization. Very long and thin chain-like gigantic macromolecules make up the class of materials, called polymers. These materials have redefined our contemporary civilization, through clothing, building materials, automobile, and aircraft parts, and much more. One of the key features required in polymeric materials so that they will be useful as end-products with market value, is the ability to make crystals from them. But this macromolecular process must be an impossible task as can be easily envisaged by considering a large number of long and intermingled wires which are all tangled up. How can they organize neatly into crystals? In fact, the molecules do indeed form crystals, at least partially. In spite of the prevalence of such partially ordered polymeric crystals in the multi-billion-dollar industry of polymers, this process is not understood. A molecular understanding of the crystallization process of polymeric materials is one of the longstanding research challenges in the world of materials. The multitude of puzzles collected phenomenologically over many decades in this field demands a rational conceptual foundation, which will facilitate discoveries of new materials in addition to understanding the known facts. This research program is aimed to develop fundamental concepts to understand how polymers crystallize and melt, using theory and computer modelling. In addition to advancing the field of polymer crystallization, the proposed activities include strong support of diversity and training a new generation of graduate students enabling their future participation in the multi-billion-dollar industry of semicrystalline polymers.TECHNICAL SUMMARYThis award supports theoretical and computational research, and education to advance understanding of polymer crystallization. Crystallization of polymers from solutions and melts is one of the longstanding research areas in polymer science with tremendous industrial value. Due to enormous number of conformations that can be taken up by flexible macromolecules, their crystallization and melting behaviors exhibit a broad range of puzzling phenomenology which has been challenging to understand. These puzzles emerge from rich structural hierarchies at multiple length scales and time scales often involving long-lived non-equilibrium states. This research program is aimed to develop new theories of polymer crystallization, melting, and the interlude of hierarchy of metastable states. Building on new insights into the role of long-lived metastable states and memory effects in semicrystalline polymers, the proposed research will be performed using statistical mechanics, field theory, and several simulation techniques. Specifically, the PI plans to address: (i) interlude of metastable states in crystallization, melting, and memory, (ii) vertical crystallization by lamellar stacking, (iii) spontaneous selection and amplification of chirality, and (iv) instability of interlamellar amorphous regions. The results from the research program are expected to have significant impact in numerous industrially relevant areas such as polymer processing. Most of the materials today are made from processed semicrystalline polymers, which form the focus of the proposed work. These materials constitute a multi-billion-dollar industry. A fundamental understanding of this important class of materials will help to design and process novel polymeric materials with enhanced benefits to our society. Training of graduate students and postdoctoral researchers in this challenging research area is a strong educational component of the research program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.