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，延长食物储存时间，并有助于治疗疾病。虽然这些多功能材料使人口扩张和全球化成为可能，但新的需求已经出现：能够制造具有下一代挑战所需功能特性的大容量塑料，同时将可持续性纳入材料设计。为了应对这一挑战，位于查佩尔山的北卡罗来纳州大学的Leibfarth教授的研究团队开发了合成方法，以精确控制聚合物结构并使用来自生物可再生资源的构建块。实现该项目中列举的目标将为科学界和更广泛的人群做出重大贡献，既贡献新的基础知识，又为当代社会挑战引入新的材料解决方案。这项高分子化学的基础研究与一项教育计划相结合，该计划开发了以探究为指导的科学活动，以教育并为长期住院的儿童带来发现的乐趣。这个服务不足的群体的年龄范围从K-12。这些患者/学生无法获得与同龄人相同的互动科学体验。Leibfarth教授和他的团队创建了结构化模块，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。六个可扩展的模块，可以在一系列的医院设置实施，可在儿童医院，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得。 此外，研究生还接受了与不同患者群体互动和与公众交流科学的正式培训，建立了一个重视多样性和外联重要性的可持续群体文化。乙烯基聚合物的立构规整性（立体化学）与其所得材料性能密切相关。尽管用于丙烯和其它非极性α-烯烃的聚合的立体选择性方法发展良好，但极性乙烯基单体的立体选择性聚合已被证明更具挑战性。 Leibfarth集团最近开发了催化剂，在阳离子聚合过程中系统地偏置链端立体化学环境，并使全同立构聚（乙烯基醚）的合成具有前所未有的全同立构。 在NSF化学部的大分子、超分子和纳米化学计划的支持下，Leibfarth小组寻求对这种聚合方法有更深入的基本了解。 该项目的第一个目标是研究单体的立体和手性对反应性能的影响，以了解使催化剂能够直接立体选择性聚合这些单体的相互作用。第二个目标寻求扩大适合于立体选择性聚合的化学官能度的多样性并探索策略（例如，连续流动方法）来控制聚合物的分子量和分子量分布。第三个目标是利用整个项目中获得的基本理解，开发一类新的生物可再生乙烯基醚单体，这些单体适合立体选择性聚合。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。

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.