美国阿克伦大学Junpeng Wang团队研究了稠环环辛烯的结构-聚合热力学关系以开发化学可回收聚合物。相关研究成果于2022年1月5日发表在《美国化学会杂志》。

通过循环使用材料，可化学回收其组成单体的聚合物为解决塑料可持续性方面的挑战提供了一个有希望的解决方案。下一代化学可回收聚合物单体的设计和开发需要了解单体/聚合物结构与聚合/解聚热力学之间的关系。

该文中，研究人员研究了一系列环辛烯单体的结构-聚合热力学关系，这些单体包含一个在5,6-位置熔融的附加环，包括反式环丁烷、反式环戊烷和反式五元环缩醛。四元环和五元环与环辛烯的反式熔融降低了单体的环应变能，聚合焓变化范围为2.1至3.3 kcal mol^–1。尽管焓变范围很窄，但由于熵变小，1.0m处的最高温度范围为330至680°C，范围为2.7至5.0 cal mol^–1 K^–1。

重要的是，发现反式五元环缩醛稠合环辛烯上的双子取代基可将最高温度降低约300℃，尽管它们不直接连接到环辛烯。远程gem双取代基效应可用于促进相应聚合物的解聚并调节其热机械性能。

附：英文原文

Title: Understanding the Structure–Polymerization Thermodynamics Relationships of Fused-Ring Cyclooctenes for Developing Chemically Recyclable Polymers

Author: Junfeng Zhou, Devavrat Sathe, Junpeng Wang

Issue&Volume: January 5, 2022

Abstract: Polymers that can be chemically recycled to their constituent monomers offer a promising solution to address the challenges in plastics sustainability through a circular use of materials. The design and development of monomers for next-generation chemically recyclable polymers require an understanding of the relationships between the structure of the monomers/polymers and the thermodynamics of polymerization/depolymerization. Here we investigate the structure–polymerization thermodynamics relationships of a series of cyclooctene monomers that contain an additional ring fused at the 5,6-positions, including trans-cyclobutane, trans-cyclopentane, and trans-five-membered cyclic acetals. The four- and five-membered rings trans-fused to cyclooctene reduce the ring strain energies of the monomer, and the enthalpy changes of polymerizations are found to be in the range of 2.1 to 3.3 kcal mol–1. Despite the narrow range of enthalpy changes, the ceiling temperatures at 1.0 M span from 330 to 680 °C, due to the low entropy changes, ranging from 2.7 to 5.0 cal mol–1 K–1. Importantly, geminal substituents on the trans-five-membered cyclic acetal fused cyclooctenes are found to reduce the ceiling temperature by ～300 °C, although they are not directly attached to the cyclooctene. The remote gem-disubstituent effect demonstrated here can be leveraged to promote depolymerization of the corresponding polymers and to tune their thermomechanical properties.

DOI: 10.1021/jacs.1c11197

Source: https://pubs.acs.org/doi/10.1021/jacs.1c11197