CAS: Lewis Pair Polymerization: Compounded Sequence and Spatiotemporal Controls for Precision Synthesis of Sustainable Linear and Cyclic Block Copolymers

在化学系大分子、超分子和纳米化学项目的支持下，科罗拉多州立大学的Eugene Y.Chen教授正在开发新的合成路线，用于从生物基可再生单体构建具有重要技术意义的环状聚合物和共聚物。环状聚合物是一类有趣的没有链端的大分子。与线性聚合物相比，这些聚合物通常具有更低的粘度、更快的结晶动力学，有时还具有更高的抗化学和热降解性。这些特性使环状聚合物非常适合于各种重要的工业应用。该项目将利用合成、催化和机械方法制备各种环状聚合物和共聚物，目的是精确控制单体单元的结构和序列。通过已建立的国际合作，计算方法将进一步指导实验设计。这项合成工作有可能有助于在足够大的规模上提供精确的常规和嵌段环状聚合物，以便更广泛的聚合物社区进行结构/性能关系研究。从可持续性的角度来看，与该项目相关的设计原则有可能有助于促成一场翻天覆地的变化，从而使可回收和可升级的聚合物得到更广泛的生产，并用作商品塑料。与该项目相关的活动旨在扩大参与范围，并使本科生和研究生能够在聚合物化学方面进行培训，并致力于开发和推广比目前通常做法更可持续的方法。在这项工作中，Lewis对聚合(LPP)将用于环状聚合物和共聚物的定制合成。LPP利用Lewis对(LP)的酸和碱之间的协同和协同作用来影响单体的活化、链引发、繁殖、终止和转移事件。与其他聚合方法相比，这种协同双组分催化机理提供了几个优点，特别是在一步精确合成中的复合顺序控制和时空控制方面。环状聚合物(CP)的研究历来少于其线型聚合物，这主要是由于对这类有趣的聚合物的合成途径有限。该项目的具体目标包括：(1)更好地从根本上了解决定精密CP和环状嵌段共聚物(CBCP)合成的空间和时间控制的因素；(2)通过一锅一步地合成生物基丙烯酸单体的LPP来合成高阶多BCP；以及(3)利用手性双核LP作为促进剂，构建由可再生的乙烯基内酯衍生的立体规则和可回收的CP。该奖项反映了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。

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professor Eugene Y. Chen of Colorado State University is developing new synthetic routes for the construction of technologically important cyclic polymers and copolymers from bio-based renewable monomers. Cyclic polymers are an intriguing class of macromolecules that lack chain ends. When compared to linear counterparts, these polymers typically have lower viscosity, faster crystallization kinetics, and sometimes higher resistance to chemical and thermal degradation. These properties make cyclic polymers ideally suited for a variety of industrially important applications. The project will utilize synthetic, catalytic, and mechanistic approaches to prepare a variety of cyclic polymers and copolymers with the aim of precisely controlling the structures and sequences of monomer units. Computational methods through established international collaborations will further guide experimental design. The synthetic work has the potential to help provide precision regular and block cyclic polymers at a scale large enough for structure/property relationship studies to be conducted by the broader polymer community. From the point of view of sustainability, the design principles associated with this project have the potential to help nucleate a sea change, whereby recyclable and upcyclable polymers are more widely produced and used as commodity plastics. The activities associated with this project are intended to broaden participation and enable the training of undergraduate and graduate students in polymer chemistry, with a distinct effort to develop and promote more sustainable approaches than are typically practiced today.In this work, Lewis pair polymerization (LPP) will be used for tailored synthesis of cyclic polymers and copolymers. LPP exploits the synergy and cooperativity between an acid and a base of a Lewis pair (LP) to effect monomer activation, chain initiation, propagation, termination, and transfer events. This cooperative two-component catalytic mechanism provides several advantageous features when compared to other polymerization methods, particularly with respect to compounded sequence control and spatiotemporal control in one-step precision synthesis. Cyclic polymers (CPs) have historically been less studied than their linear counterparts, which is mainly due to limited synthetic access to this interesting class of polymers. Specific objectives of the project include: (1) developing a better fundamental understanding of the factors that determine spatial and temporal control in the synthesis of precision CPs and cyclic block copolymers (cBCPs), (2) synthesizing higher-order multi-BCPs by LPP of bio-based acrylic monomers in one pot and one step, and (3) constructing stereoregular and recyclable CPs derived from renewable vinyl lactones utilizing chiral dinuclear LPs as promoters.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.