School of Chemistry, University of Birmingham, Birmingham B15 2TT, U.K.
J Am Chem Soc. 2022 Jul 6;144(26):11729-11735. doi: 10.1021/jacs.2c03525. Epub 2022 Jun 24.
The development of photopolymers that can be depolymerized and subsequently re-cured using the same light stimulus presents a significant technical challenge. A bio-sourced terpenoid structure, l-carvone, inspired the creation of a re-curable photopolymer in which the orthogonal reactivity of an irreversible thioether and a dynamic thiol-Michael bond enables both photopolymerization and thermally driven depolymerization of mechanically robust polymer networks. The di-alkene containing l-carvone was partially reacted with a multi-arm thiol to generate a non-crosslinked telechelic photopolymer. Upon further UV exposure, the photopolymer crosslinked into a mechanically robust network featuring reversible Michael bonds at junction points that could be activated to revert, or depolymerize, the network into a viscous telechelic photopolymer. The regenerated photopolymer displayed intrinsic re-curability over two recycles while maintaining the desirable thermomechanical properties of a conventional network: insolubility, resistance to stress relaxation, and structural integrity up to 170 °C. Our findings present an on-demand, re-curable photopolymer platform based on a sustainable feedstock.
开发可使用相同光刺激解聚并随后再固化的光聚合剂提出了重大的技术挑战。萜烯结构的生源 l-香芹酮激发了可再固化光聚合剂的产生，其中不可逆硫醚和动态硫醇-Michael 键的正交反应性既能够实现光聚合，又能够驱动机械坚固聚合物网络的热解聚。含有二烯烃的 l-香芹酮与多臂硫醇部分反应，生成非交联遥爪光聚合物。进一步的紫外线照射下，光聚合物交联成机械坚固的网络，在连接点处具有可逆的迈克尔键，可以将网络激活还原或解聚成粘性遥爪光聚合物。再生光聚合物在两次循环中显示出固有可再固化性，同时保持传统网络的理想热机械性能：不溶性、抗应力松弛性和结构完整性，最高可达 170°C。我们的研究结果提出了一种基于可持续原料的按需、可再固化光聚合平台。
