Cyclic Polymers: Topological Effects on Structure, Dynamics and Function

环状聚合物：拓扑对结构、动力学和功能的影响

• 批准号: 1001903
• 负责人: Robert Waymouth
• 金额: $ 38.4万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2013-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1001903&HistoricalAwards=false
• 关键词: Cyclic; Polymers; Topological; Effects; Structure

TECHNICAL SUMMARY:Macromolecules are ubiquitous in modern technologies. Cyclic macromolecules have fascinated chemists, biologists and materials scientists for decades. While the properties of linear macromolecules are reasonably well understood, the properties of cyclic macromolecules remain mysterious. Constraining a large macromolecule into a ring has a significant influence its structure, dynamics and properties. Our ability to exploit these novel properties to generate new classes of materials is constrained both by our understanding and our inability to generate high molecular weight cyclic polymers with well defined structures in high purity. An innovative zwitterionic ring-expansion polymerization of lactones was discovered that provides an expedient synthesis of high molecular weight cyclic polyesters of well-defined molecular weight and narrow molecular weight distribution. This new synthetic strategy is fast, scalable and enables the generation of crystalline cyclic polyesters that span molecular weights where chain-entanglements begin to dominate their properties. Our experimental approach combines mechanistic studies of polymerization reactions with physical, rheological and spectroscopic investigations (wide- and small-angle X-ray and neutron scattering) to illuminate the role of molecular topology on macromolecular conformation, dynamics and properties. The gaps in our fundamental understanding of one of the simplest topological isomers of linear macromolecules are specific targets of the proposed studies. The experimental plan is designed to provide new knowledge to fill these gaps and to apply this knowledge for the development of new classes of high-performance thermoplastics, elastomers, and smart rheological fluids. While the focus is cyclic polyesters, the fundamental insights derived should be generalizable to any cyclic macromolecule, highlighting the broader intellectual impacts of the proposed studies NON-TECHNICAL SUMMARY: Plastics are ubiquitous modern materials, which impact every facet of our lives. Most plastics are derived from linear polymers, long linear chain macromolecules whose properties are reasonably well-understood. In contrast, cyclic polymers, large macromolecules closed into a ring exhibit unusual properties quite different from their linear analogs, but these differences are not well-understood. Our ability to exploit these novel properties to generate new classes of materials is limited both by our understanding and our inability to generate high molecular weight cyclic polymers with well defined structures in high purity. A new synthetic technique was developed that provides a means of generating cyclic polyesters. This new method will enable the preparation of new classes of well-defined cyclic polymers to investigate their properties and possible applications as new classes of polymeric materials. Studies will address how cyclic polymers crystallize into hard thermoplastics, how they flow when melted, and how the simple fact that their ends are connected into a ring changes their behavior. That so little is known about cyclic polymers implies that our understanding of polymers is far less sophisticated than previously imagined. That is, if connecting the ends of a large linear molecule changes its properties in ways that can't be explained, can it be said that we understand these large molecules? A major impact of the proposed studies will be new scientific understanding on the behavior of macromolecules constrained in rings and the degree to which these new insights challenge and augment our current understanding of macromolecular behavior. As new insights emerge, the novel properties of cyclic polymers can be harnessed to create new families of materials. Collaborative efforts with industrial scientists at IBM, physical scientists at NIST, and chemical engineers at Stanford will provide a unique training environment for the next generation of scientists who are able to make new classes of materials, study their properties and use these insights to generate new classes of polymeric materials.

技术摘要：大分子在现代技术中无处不在。 几十年来，环状大分子吸引了化学家，生物学家和材料科学家。 虽然对线性大分子的特性相当理解，但环状大分子的特性仍然是神秘的。 将大的大分子限制在环中具有重大影响其结构，动力学和性质。我们利用这些新型特性生成新的材料类别的能力受到我们的理解和无法产生高纯度结构良好的结构的高分子量循环聚合物的限制。 发现了内酯的创新性zwittionic环膨胀聚合聚合，该聚合提供了具有定义明确的分子量和狭窄的分子量分布的高分子量循环聚酯的权宜合成。 这种新的合成策略是快速，可扩展的，并且能够生成跨越分子量的晶体循环多植物，其中链 - 键入开始主导其性能。 我们的实验方法结合了聚合反应的机理研究与物理，流变和光谱研究（广角和小角度X射线和中子散射），以阐明分子拓扑在大分子构象，动力学，动力学和性质中的作用。 我们对线性大分子最简单的拓扑异构体之一的基本理解的差距是所提出的研究的特定目标。 实验计划旨在提供新的知识来填补这些空白，并将这些知识应用于新的高性能热塑性，弹性体和智能流变液的开发。虽然重点是循环多种植者，但得出的基本见解应推广到任何环状大分子，强调了拟议研究的非技术摘要的更广泛的智力影响：塑料是无处不在的现代材料，这会影响我们生活的每个方面。 大多数塑料源自线性聚合物，长线性链大分子，其特性相当理解。 相反，循环聚合物，大的大分子封闭在一个环中，表现出与线性类似物完全不同的异常特性，但是这些差异并没有得到很好的理解。 我们利用这些新型特性生成新材料的能力受到我们的理解和无法产生高纯度结构良好结构的高分子量循环聚合物的限制。开发了一种新的合成技术，该技术提供了一种生成循环多种植者的方法。 这种新方法将使新的定义循环聚合物的新类别制备，以研究其特性和可能作为新类别的聚合物材料的应用。 研究将介绍环状聚合物如何结晶成硬热塑料，它们在融化时如何流动以及如何将其末端连接到环的简单事实改变其行为。 关于环状聚合物的知之甚少，这意味着我们对聚合物的理解远没有以前想象的要复杂。 也就是说，如果连接大型线性分子的末端以无法解释的方式改变其性能，可以说我们了解这些大分子吗？ 拟议的研究的主要影响将是对在环上约束的大分子的行为以及这些新见解挑战和增强我们当前对大分子行为的理解的程度的新科学理解。 随着新的见解的出现，可以利用循环聚合物的新型特性来创建新的材料系列。 与IBM的工业科学家，NIST的物理科学家以及斯坦福大学的化学工程师的合作努力将为下一代科学家提供独特的培训环境，这些科学家能够制造新的材料，研究其特性并使用这些见解来生成新的聚合物材料。