CAS: Dithioacetal as a Highly Tunable and Versatile Bond for the Design of Chemically Recyclable and Dynamic Covalent Polymers

CAS：二硫缩醛作为高度可调和多功能的键，用于化学可回收和动态共价聚合物的设计

• 批准号: 2305045
• 负责人: Ying Yang
• 金额: $ 45.16万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2305045&HistoricalAwards=false
• 关键词: CAS; Dithioacetal; Highly; Tunable; Versatile

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Ying Yang of the University of Nevada at Reno is using ring-opening and -closing polymerization strategies to prepare recyclable polydithioacetals. Polydithioacetals are long chain macromolecules in which the main polymer backbone contains chemical element sulfur in addition to carbon commonly seen in commodity plastics. This class of polymers is chemically stable and yet has highly modifiable backbones and side groups. As a result, polydithioacetals are promising candidates for recyclable polymers with tunable properties. Research associated with this project will develop an in-depth understanding of the polymerization mechanisms of dithioacetal polymerization, investigate how thermodynamics and kinetics of polymerization are affected by the rich structural variations, and explore using these chemistries to enable dynamic architectural transformations of thermoplastic and thermoset polydithioacetals controlled by stimuli. The results from these fundamental studies have the potential to lead to the development of novel recyclable polymers which can be reprocessed at high temperatures and depolymerized on-demand back into cyclic macrocycles. From the sustainability point of view, the design principle associated with this project provides a very promising and viable solution to the current challenges associated with the widespread usage of non-degradable vinyl plastics. Hence, the developed methodology could be utilized to build readily degradable and sustainable plastics that are amenable to a circular economy life cycle. The research team will be actively involved in disseminating the results via publications and presenting the work at conferences and local events. Furthermore, community outreach will be conducted by establishing close relationships with Hug High School which has a large Hispanic student population. The project will also facilitate the research and education of polymer science at the University of Nevada Reno by integrating polymer chemistry modules into the large general chemistry classes.This research will focus on studying polydithioacetals that are capable of reversible entropy-driven ring-opening polymerization (ED-ROP) and ring-closing depolymerization (RCD) as a versatile platform for the development of recyclable polymers, as well as dynamic covalent systems. The dynamics will be enabled by acid-catalyzed dithioacetal exchange reactions. Building on promising preliminary results, the project aims to develop a detailed understanding of the chemistry and thermodynamics of ED-ROP for dithioacetal macrocycles through three interconnected objectives: (1) understand the polymerization mechanism with different initiator/catalyst systems and obtain controlled “living” cationic polymerization, (2) vary the structures of polydithioacetal backbones and side groups/chains and study their effects on the monomer-polymer equilibrium, and (3) develop reprocessable and depolymerizable polydithioacetal thermosets with controlled degradation by light and mechanical force. These research activities have a strong sustainability component and the potential to generate fundamental chemistry knowledge of relevance to using ED-ROP for the development of inherently practical, recyclable and functional polymers.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.

在化学系高分子、超分子和纳米化学项目的支持下，内华达大学里诺分校的Ying Yang正在利用开环聚合策略制备可回收的聚二硫缩醛，其中聚二硫缩醛是长链大分子。聚合物主链除了商品塑料中常见的碳之外还含有化学元素硫，此类聚合物化学性质稳定。具有高度可修饰的主链和侧基，因此，聚二硫缩醛是具有可调性能的可回收聚合物的有前途的候选者，与该项目相关的研究将深入了解二硫缩醛聚合的聚合机理，研究聚合的​​热力学和动力学。受到丰富的结构变化的影响，并探索使用这些化学物质来实现受刺激控制的热塑性和热固性聚二硫缩醛的动态结构转变。这些基础研究有可能导致新型可回收聚合物的开发，这些聚合物可以在高温下再加工并按需解聚回环状大环。从可持续性的角度来看，与该项目相关的设计原理提供了非常有前途的方案。因此，研究团队可以利用所开发的方法来制造易于降解且可持续的塑料，以适应循环经济生命周期。将积极参与通过出版物传播研究结果并在会议和当地活动中展示研究成果。此外，还将通过与拥有大量西班牙裔学生的 Hug 高中建立密切关系来开展社区外展活动。内华达大学里诺分校的高分子科学教育，将高分子化学模块整合到大型普通化学课程中。这项研究将重点研究能够进行可逆熵驱动开环聚合 (ED-ROP) 的聚二硫缩醛和闭环解聚（RCD）作为开发可回收聚合物以及动态共价系统的通用平台，将通过酸催化的二硫缩醛交换反应来实现，该项目旨在开发一种通过三个相互关联的目标，详细了解二硫缩醛大环化合物的 ED-ROP 的化学和热力学：(1) 了解不同引发剂/催化剂体系的聚合机理并获得受控的“活性”阳离子聚合，（2）改变聚二硫缩醛主链和侧基/链的结构，并研究它们对单体-聚合物平衡的影响，以及（3）开发可再加工和可解聚的聚二硫缩醛热固性材料，并通过光和机械力进行受控降解这些研究活动具有很强的可持续性成分，并且有可能产生与使用 ED-ROP 开发本质上实用、可回收和功能性相关的基础化学知识。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。