George & Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science & Engineering, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States.
ACS Macro Lett. 2022 Apr 19;11(4):441-446. doi: 10.1021/acsmacrolett.2c00091. Epub 2022 Mar 15.
Polymeric materials comprised of all-carbon backbones are ubiquitous to modern society due to their low cost, impressive robustness, and unparalleled physical properties. It is well-known that these materials often persist long beyond their intended usage lifetime, resulting in environmental accumulation of plastic waste. A substantial barrier to the breakdown of these polymers is the relative chemical inertness of carbon-carbon bonds within their backbone. Herein, we describe a photocatalytic strategy for cleaving carbon-based polymer backbones. Inclusion of a low mole percent of a redox-active comonomer allows for a dramatic reduction in polymer molecular weight upon exposure to light. The -(acyloxy)phthalimide comonomer, upon reception of an electron from a single-electron transfer (SET) donor, undergoes decarboxylation to yield a backbone-centered radical. Depending on the nature of this backbone radical, as well as the substitution on neighboring monomer repeat units, a β-scission pathway is thermodynamically favored, resulting in backbone cleavage. In this way, polymers with an all-carbon backbone may be degraded at ambient temperature under metal-free conditions.
由于成本低、坚固耐用且具有无与伦比的物理性能，全碳骨架的聚合材料在现代社会中无处不在。众所周知，这些材料往往会在预期使用寿命之外长时间存在，导致塑料废物在环境中积累。这些聚合物难以分解的一个主要障碍是其主链中碳-碳键的相对化学惰性。在此，我们描述了一种用于裂解碳基聚合物主链的光催化策略。在掺入低摩尔百分比的氧化还原活性共聚单体后，聚合物在暴露于光下时的分子量会大幅降低。邻苯二甲酰亚胺共聚单体在从单电子转移 (SET) 供体接收一个电子后，会发生脱羧反应生成主链中心自由基。根据该主链自由基的性质以及相邻单体重复单元上的取代基，β-断裂途径在热力学上是有利的，导致主链断裂。通过这种方式，在无金属条件下，全碳主链的聚合物可以在环境温度下降解。
