Development of Stereospecific Controlled/Living Radical Polymerization Using Rationally Engineered Chain-End Capping Agents

在化学系大分子，超分子和纳米化学项目的支持下，耶鲁大学的Mingjiang Zhong将开发新方法，用于有效制备具有立体化学控制的聚合物。聚合物的立体化学源于连接到主链上的侧基的取向，并且对重要的材料性质具有显著影响，包括机械刚度、韧性、热行为、结晶度和溶解度。调整聚合物的立体化学可以显著改变聚合物的性质，因此可以导致许多聚合物的新应用。然而，目前现有的方法来实现控制立体化学的范围是有限的，有新的方法开发的空间。该项目旨在建立与传统方法相比与更广泛的构建模块兼容的方法，这些方法可以在环境友好的溶剂中进行，并为立体控制获得新的功能材料提供途径。与该项目相关的研究活动预计将在机械坚固材料的合成以及具有重要生物医学用途的材料方面产生更广泛的科学影响。相关的教学、指导和推广活动将为不同的学员群体创造教育机会。该项目提出了通过自由基聚合合成全同立构聚合物的新方法。在受控/活性自由基聚合中，将合成刘易斯酸束缚的稳定自由基物种以通过限制链端构象来控制聚合物立构规整度。一系列稳定的自由基物种将被探索，在一系列的反应溶剂和拴系配体的目标是扩大可聚合单体的空间。Zhong研究团队还将研究聚合机制，旨在更深入地了解这种催化体系。 其中的机制功能进行检查包括刘易斯酸协调单体单元，链端构象自由基加成过程中，和自由基失活过程的动力学和热力学。这些催化剂的成功开发和应用将具有重要意义，特别是因为它们有可能为自由基加成中的立体控制这一重要问题提供一种新的方法。这项研究还具有潜在的工业化学影响，由于自由基聚合的优势，需要酸性或碱性条件下的聚合条件，与自由基聚合的方法通常表现出更大的官能团耐受性和温和的反应条件。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Mingjiang Zhong of Yale University will develop new methods for the efficient preparation of polymers with control of stereochemistry. Stereochemistry of polymers originates from the orientation of pendant groups attached to the main backbone and has a significant influence on important materials properties, including mechanical stiffness, toughness, thermal behavior, crystallinity, and solubility. Tuning the stereochemistry of polymers can dramatically change the properties and therefore can lead to new applications of many polymers. However, currently existing methods to achieve control over stereochemistry are somewhat limited in scope; there is room for new methods development. This project aims to establish methods that are compatible with a broader scope of building blocks compared to traditional approaches, that can be carried out in environmentally friendly solvents, and that provide pathways for stereocontrolled access to new functional materials. The research activities affiliated with this project are expected to have broader scientific impact in the synthesis of mechanically robust materials, as well as materials with important biomedical uses. The associated teaching, mentoring, and outreach activities will create educational opportunities for a diverse group of trainees.This project proposes new approaches to synthesizing isotactic polymers via radical polymerization. Lewis acid-tethered stable radical species will be synthesized to control polymer tacticity via confined chain end conformation in controlled/living radical polymerizations. An array of stable radical species will be explored, across a range of reaction solvents and tethered ligands with the goal of expanding the space of polymerizable monomers. The Zhong research team will also investigate polymerization mechanisms with the aim of developing a deeper understanding of this catalytic system. Among the mechanistic features to be examined are included Lewis acid coordination to monomer units, chain end conformation during radical addition, and the kinetics and thermodynamics of the radical deactivation process. The successful development and deployment of these catalysts would be significant, particularly because they have the potential to provide a new approach to the important problem of stereocontrol in radical addition. This research also has potential industrial chemical implications due to the advantages of radical polymerization over polymerization conditions that require acidic or basic conditions, with radical polymerization approaches generally exhibiting greater functional group tolerance and milder reaction conditions.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.