CAREER: A new class of polar thermoplastics: Mechanistic investigations into the synthesis of isotactic poly(vinyl ethers)

合成聚合物保护人们免受极端天气的影响，使食物能够长时间储存，并有助于治愈疾病。虽然这些多功能材料使人口扩张和全球化成为可能，但也出现了一种新的需求：能够制造具有下一代挑战所需的功能特性的大批量塑料，同时将可持续性纳入材料设计。为了应对这一挑战，北卡罗来纳大学教堂山分校的莱布法思教授的研究团队开发了合成方法，以实现对聚合物结构的精确控制，并使用来自生物可再生资源的构建块。实现本项目列举的目标将对科学界和广大民众作出重大贡献，无论是在贡献新的基本知识方面，还是在为当代社会挑战引入新的物质解决方案方面都是如此。这项聚合物化学的基础研究与一个教育项目相结合，该项目开发以探究为导向的科学活动，教育并将发现的喜悦带给长期住院的儿童。这一服务不足的群体的年龄从K到12岁不等。这些患者/学生不能获得与他们的同龄人相同的互动科学体验。莱布法斯教授和他的团队创建了结构化的模块，通过动手和多媒体活动的互动组合，向住院患者介绍聚合物科学的当代方面。北卡罗来纳大学儿童医院提供了六个可在各种医院环境中实施的可扩展模块，每年将影响50多名患者。详细的说明和多媒体资源可在网上公开获取。此外，研究生在与不同的患者群体互动和与公众交流科学方面接受正式培训，建立一种可持续的群体文化，重视多样性和外向感的重要性。乙烯基聚合物的规律性(立体化学)与其合成的材料性能密切相关。尽管丙烯和其他非极性α-烯烃的立体选择性聚合方法已经发展得很好，但极性乙烯基单体的立体选择性聚合被证明是更具挑战性的。Leibfarth集团最近开发了催化剂，这种催化剂在阳离子聚合过程中系统地偏置链端立体化学环境，并能够合成具有前所未有的同位素的全同立构聚乙烯醚S。在美国国家科学基金会化学部大分子、超分子和纳米化学项目的支持下，莱布法斯小组寻求对这种聚合方法有更深层次的基本了解。本项目的第一个目标是考察单体、立体结构和手性对反应性能的影响，以了解使催化剂能够指导这些单体的立体选择性聚合的相互作用。第二个目标旨在扩大立体选择性聚合的化学功能的多样性，并探索控制聚合物的相对分子质量和相对分子质量分布的策略(例如，连续流动方法)。第三个目标利用在整个项目中获得的基本理解来开发一种新的可生物可再生的乙烯基醚单体，这种单体可以进行立体选择性聚合。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Synthetic polymers protect people from extreme weather, enable prolonged food storage, and help cure disease. While these versatile materials have enabled population expansion and globalization, a new need has arisen: the capability to make high-volume plastics with the functional properties needed for next-generation challenges while simultaneously incorporating sustainability into the material design. To tackle this challenge, the research team of Professor Leibfarth of the University of North Carolina at Chapel Hill develops synthetic methods to enable the precise control of the polymer structure and the use of building blocks from biorenewable resources. Accomplishing the goals enumerated in this project will make significant contributions to the scientific community and the broader population, both in contributing new fundamental knowledge and in introducing novel material solutions for contemporary societal challenges. This fundamental research in polymer chemistry couples with an education program that develops inquiry-guided scientific activities to educate and bring the joy of discovery to children undergoing long-term hospitalization. This underserved group ranges in age from K-12. These patients/students not get the same interactive scientific experiences as their peers. Professor Leibfarth and his group create structured modules that introduce inpatients to contemporary aspects of polymer science through an interactive mix of hands-on and multimedia activities. Six scalable modules that can be implemented across a range of hospital settings are available at UNC Children's Hospital and will impact 50+ patients per year. Detailed instructions and multimedia resources are publicly available online. In addition, graduate students receive formal training in interacting with diverse patient populations and communicating science with the public, building a sustainable group culture that values the importance of diversity and outreach.The tacticity (stereochemistry) of vinyl polymers is intimately linked to their resultant material properties. Despite the well-developed stereoselective methods for the polymerization of propylene and other nonpolar alpha-olefins, stereoselective polymerization of polar vinyl monomers has proven more challenging. The Leibfarth group has recently developed catalysts that systematically bias the chain-end stereochemical environment during cationic polymerization and enable the synthesis of isotactic poly(vinylether)s with unprecedented isotacticities. With the support from the Macromolecular, Supramolecular, and Nanochemistry Program of the NSF Division of Chemistry, the Leibfarth group seeks to gain a deeper fundamental understanding of this polymerization method. The first objective of this project is to examine the influence of monomer sterics and chirality on reaction performance in order to understand the interactions that enable the catalyst to direct stereoselective polymerization of these monomers. The second objective seeks to expand the diversity of chemical functionality amenable to stereoselective polymerization and explore strategies (e.g., continuous flow methods) to control the molecular weight and molecular weight distribution of the polymers. The third objective leverages the fundamental understanding gained throughout the project to develop a new class of biorenewable vinyl ether monomers that are amenable to stereoselective polymerization.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.