Improvement in persistent room temperature phosphorescence of polymeric systems via a melt‐pressing method

Abstract

Polymer‐based afterglow materials with persistent room temperature phosphorescence (pRTP) have attracted ever‐increasing attention due to their excellent mechanical property, suitability for large‐area production, and diverse processing methods. However, most pRTP polymers were solution‐processed into the films via casting. Herein, a simple processing method of melt‐pressing was proposed, which can improve the phosphorescence of various emitters when doped into polyamide‐12 (PA12) or its copolymer PA4 matrix. Notably, for Be@PA4 and Ch@PA4 (benzo[c]phenanthrene, Be and chrysene, Ch), their casted films did not show any afterglow, while the melt‐pressed ones exhibited bright afterglow of over 4.0 s, even if there were no hydrogen or ionic interaction between the emitters and the matrix. Detailed investigations demonstrate the melt‐pressing procedure can increase the non‐covalent interaction among the matrix as well as offer a rigid and dense environment. The melt‐pressed RTP improvement strategy was also applied to other polar polymers. Additionally, the melt‐pressing method would be of great potential in high‐level anti‐counterfeiting like preparing colorful camouflage patterns. Therefore, we offered a feasible method of melt‐pressing to improve the phosphorescence of polymeric materials without a change in chemical composition or feeding ratio. This work also gained a deeper understanding of the luminescence of polymer‐based systems.