Lewis Pair Polymerization: Controlling Polymer Tacticity and Topology

该项目由科罗拉多州立大学化学系的大分子、超分子和纳米化学项目资助，由该校化学系的Eugene Y. Chen教授负责开发新的合成路线，用于构建具有重要工业意义的立体规则高分子材料。立体化学是化学的一个重要方面，通常关注碳原子附着在四个不同基团上的化合物。碳原子上基团的特殊排列产生了不能叠加的镜像；这些镜像被称为手性分子，它们成对出现。（值得注意的是，人类的手也是手性的，因为左手是右手的镜像，但一个人不能转动或移动一只手，使另一只手看起来完全一样。）手性是决定化合物或材料的生物、热和机械性能的性质。以聚合物为例，聚合物是由大量碳原子连接而成的大分子，手性可能性的数量可能非常大。例如，在仅由30个碳原子组成的相对较小的聚合物中，唯一手性构型的最大数量估计为10亿个。本研究开发了复杂的方法，在聚合物制备过程中控制和微调手性产物的数量，产生了一种全新的、以前未开发的塑料材料。与该奖项相关的活动增加了广泛的参与，并使本科生和研究生能够在工业上重要的聚合物化学领域得到培训。在这项工作中，开发了下一代刘易斯对聚合（LLP）系统，该系统可以控制所得到聚合物的立体化学结果和拓扑结构，从而可以方便地获得具有不同战术或立体微观结构和循环拓扑结构的先进聚合物材料。LLP方法依赖于一个相互作用或受挫的刘易斯对（LP），并利用LP的刘易斯酸性和碱性位点之间的协同作用和协同性来影响单体的协同活化以及链的起始、传播、终止和转移事件。研究包括合成、催化和机械方法，并结合协同的理论和计算方法。研究的单体包括工业上重要的极性乙烯基单体和克罗宁酯。后一种单体提供了目前其他合成方法无法获得的独特的双链聚合物。此外，在丙烯酸单体的LPP中，拓扑和立体化学控制使得手性螺旋或非手性形式的环丙烯酸聚合物的选择性合成成为可能。这项工作的研究具有高度的创新性和变革性，不仅对聚合物化学领域，而且对合成有机化学和催化领域都有重大影响。通过精心设计和计划的活动，研究团队为控制战术性提供了切实可行的解决方案，战术性一直是现代合成聚合物化学的主要弱点之一。该奖项反映了美国国家科学基金会的法定使命，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。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Eugene Y. Chen of the Department of Chemistry at Colorado State University is developing new synthetic routes for the construction of industrially-important stereoregular polymeric materials. Stereochemistry is an essential aspect of chemistry that generally focuses on compounds in which carbon atoms are attached to four different groups. The specific arrangement of the groups on a carbon gives rise to mirror images that cannot be superimposed; These mirror images are called chiral molecules and they occur in pairs. [Notably, human hands are also chiral because the left hand is a mirror image of the right hand, but one cannot turn or move one of the hands to look exactly the same as the other.] Chirality is property that dictates biological, thermal and mechanical properties of compounds or materials. In the case of polymers, which are large molecules made by linking a large number of carbons together, the number of chiral possibilities can be very large. For example, in a relatively small polymer consisting of only 30 carbon atoms, the maximum number of unique chiral configurations is estimated at a billion. This research develops sophisticated methodologies that control and fine tune the number of chiral outcomes during the preparation of polymers, yielding a completely new and previously unexplored class of plastic materials. The activities associated with this award increase broadening participation and enable training of undergraduate and graduate students in the industrially-important field of polymer chemistry.In this work, a next generation Lewis pair polymerization (LLP) system is developed that can control the stereochemical outcomes and topologies of the resulting polymers, thereby enabling facile access to advanced polymeric materials with different tacticities or stereomicrostructures and cyclic topological structures. LLP methodology relies on an interacting or frustrated Lewis pair (LP) and exploits the synergy and cooperativity between the Lewis acidic and basic sites of LPs to effect cooperative monomer activation as well as chain initiation, propagation, termination and transfer events. The research includes synthetic, catalytic and mechanistic approaches, coupled with synergistic theoretical and computational methods. Investigated monomers include industrially-important polar vinyl monomers and crotonic esters. The latter monomers provide access to unique ditactic polymers which are currently unobtainable by other synthetic methods. Additionally, topological and stereochemical control in the LPP of acrylic monomers enables selective synthesis of cyclic acrylic polymers in chiral helical or achiral forms. The research in this work is highly innovative and transformative with the potential to significantly impact not only the field of polymer chemistry, but also synthetic organic chemistry and catalysis in general. Through carefully designed and planned activities, the research team provides tangible solutions to the control of tacticity, which has been traditionally one of the main weaknesses in modern synthetic polymer chemistry.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.