Materials from High Molecular Weight Cyclic Polymers: Insights on Properties and Dynamics

非技术型聚合物无处不在；这些由长链分子制成的材料包括所有现代塑料、纺织品纤维以及包括蛋白质和DNA在内的生物学关键分子。这个项目将利用一种创造大型环状聚合物的新方法来了解将一个长分子连接成一个环如何影响由这些环状结构产生的材料的性质。环聚合物与线性聚合物只有一个键不同，但这种微小的化学变化影响了这些分子在加工过程中的流动方式、它们的固化方式以及它们与环境的相互作用方式，目前尚不清楚。计划中的研究针对三个具体目标。第一个目标是从被包裹在交联分子网络中的环状聚合物衍生出新的材料类别，以研究这种缠绕的环链如何影响材料的性质。第二个目标是阐明环状分子是如何流动的，以更好地理解环状分子如何相互缠绕以及如何与线形链状分子缠绕。第三个目标集中在环状结构对这些大分子在液态和固态时所采用的形状的影响。该项目将支持和培养两名研究生，他们将有机会与来自外国和美国国家实验室的顶尖专家合作。首席调查员和研究生将参与当地学校的外展项目，以促进整个社区的科学理解。技术综述这项研究的重点是研究大环状聚合物的构象、性质和应用，利用以往合成大环链的新方法的进展。两性离子开环聚合(ZROP)通过产生同时含有正电荷端和负电荷端的传播链来产生大的环状分子。用这种方法合成的三类聚合物将被用来实现上述目标。将水溶性的环状聚磷酸酯包埋在三维的、交联的水凝胶网络中，研究被包埋的环链对形成的双网络水凝胶性质的影响。这些新型材料有望表现出相对于没有捕获链的凝胶的增强韧性。我们将研究高分子量环硅氧烷聚合物的流变行为，以阐明环状分子是如何缠绕在一起的。这些材料的长度大约是相应线性链的纠缠分子量(Me)的125倍--这是以前任何其他合成方法都无法达到的分子量范围。这些研究的目的是研究大的环链是否会表现出典型的线性链行为的平台模数。为了验证环链浓缩液将呈现塌陷构象的理论预测，将进行高相对分子质量环己内酯的中子束散射实验。该项目的跨学科性质将为接受聚合物合成培训的学生提供一个特殊的教育环境，让他们与聚合物流变学、聚合物物理、中子散射和现代色谱分离方面的世界专家互动。

NON-TECHNICAL SUMMARYPolymers are ubiquitous; these materials, made of long-chain molecules comprise all modern plastics, the fibers of textiles, and the key molecules of biology including proteins and DNA. This project will leverage a new method for creating large cyclic polymers to learn how connecting a long molecule into a ring influences the properties of materials generated from these cyclic structures. Cyclic polymers differ from linear polymers by just a single bond, but this minor chemical change influences how these molecules flow during processing, how they solidify and how they interact with their environment in ways that remain poorly understood. The planned research targets three specific aims. The first aim focuses on the generation of new classes of materials derived from cyclic polymers entrapped in cross-linked molecular networks to investigate how such an entangled cyclic chain influences the properties of the material. The second aim seeks to illuminate how cyclic molecules flow to gain a better understanding of how ring-like molecules entangle with one another and with linear chain molecules. The third aim focuses on the influence of a cyclic structure on the shapes that these large molecules adopt in the liquid and solid states. This project will suport and educate two graduate students, who will have the opportunity to collaborate with leading experts from foreign countries and at US National Labs. The Principal Investigator and the graduate students will engage in outreach programs at local schools to promote increased scientific understanding in the community at large. TECHNICAL SUMMARYThis research focuses on investigations of the conformation, properties, and applications of large cyclic polymers by leveraging previous advances in a new synthetic method for generating large cyclic chains. Zwitterionic ring opening polymerization (ZROP) produces large cyclic molecules by generating propagating chains that contain both a positively-charged end and a propagating negatively charged chain end. Three classes of polymers synthesized with this method will be used to achieve the above-stated goals. Water-soluble cyclic polyphosphoesters will be entrapped in three-dimensional, cross-linked hydrogel networks to investigate how the entrapped cyclic chains influence the properties of the resultant double-network hydrogels. These novel materials are anticipated to exhibit enhanced toughness relative to gels lacking the entrapped chains. The rheological behavior of high molecular-weight cyclic carbosiloxane polymers will be investigated to illuminate how cyclic molecules entangle. These materials are of a length approximately 125 times the entanglement molecular weight (Me) of the corresponding linear chains -- a molecular weight regime previously unattainable by any other synthetic method. These studies are aimed at investigating whether large cyclic chains can exhibit a plateau modulus that is typical of linear chain behavior. Neutron-scattering experiments of deuteriated high molecular weight cyclic polycaprolactones will be carried out to validate theoretical predictions that concentrated solutions of cyclic chains will exhibit collapsed conformations. The interdisciplinary nature of this project will provide an exceptional educational environment for students trained in polymer synthesis to interact with world experts in polymer rheology, polymer physics, neutron scattering, and modern chromatographic separations.