A Force-Responsive Phosphorescence Elastomer with 7 <i>H</i> -Benzo[ <i>c</i> ]carbazole Imbedded in the Hard Segments of PU Chains

Polymer-based room-temperature phosphorescence (RTP) generally requires a high rigidity of a polymer with a high glass-transition temperature, so constructing a phosphorescence elastomer is full of challenges. Herein, we successfully prepared a force-responsive phosphorescence PU elastomer by imbeddingAQ 7H-benzo[c]carbazole into the hard segment of the chains. The phosphorescence elastomer was synthesized through a three-step method by using PTHF, BDO, BCZ-2OH, and MDI/HDI as the agents. It is revealed that the molecular weights of PTHF, BCZ-2OH concentration, and MDI/HDI greatly affect RTP performance and elasticity. As the molecular weight of PTHF decreased, the length of the soft segment decreased, and the structural rigidity of the phosphorescent elastomer increased, inhibiting the nonradiative transition of the phosphorescent molecules and thereby strengthening the phosphorescence intensity and lifetime. Moreover, higher BCZ-2OH concentrations lead to shorter phosphorescence lifetime and lower phosphorescence intensity due to aggregation-caused phosphorescence quenching. Furthermore, the hard segment composition MDI profoundly impacts the structural rigidity and effectively promotes phosphorescence enhancement compared with HDI. Therefore, the optimized BCZ-2OH@PU phosphorescence elastomer with both excellent RTP properties and excellent elasticity was constructed with 650 Da PTHF, 0.05 wt % BCZ-2OH, and MDI. Excitingly, the phosphorescence PU elastomer exhibits a force response, namely, a stress-induced decrease in phosphorescence intensity and lifetime as external force damages the compact stacking of the hard segments and further impedes the phosphorescence process. We believe that this work will expand the scope of phosphorescence elastomer and lay the foundation for future applications of intelligent RTP materials.