A Nonaromatic Room-Temperature Phosphorescent Hydrogel with Shape Memory Effect and Ultra-High Elastic Modulus based on Partially Hydrolyzed Polyacrylonitrile

Organic room-temperature phosphorescent (RTP) hydrogels hold great potential for various applications. However, the development of hydrogels with long phosphorescence lifetimes remains challenging because of quenching by water. Moreover, achieving multifunctionality alongside long lifetimes presents additional challenges. Herein, a series of partially hydrolyzed polyacrylonitrile (PHPAN) hydrogels are prepared. The initial PHPAN-Na-ori (PHPAN-Na+-original) hydrogel exhibits RTP, and the hydrogel treated with Zn2+ and a heating-cooling process, namely the PHPAN-Zn-hc hydrogel, exhibits a long phosphorescence lifetime of 178.48 ms, an ultra-high elastic modulus of 161 MPa, and a shape memory effect. Experiment results show that the phosphorescence of the PHPAN-Na-ori hydrogel originates form the hydrophobic aggregation of the cyano groups, and the photoluminescent and mechanical characteristics of the PHPAN-Zn-hc hydrogel is because Zn2+ forms coordinate bond with carboxylate and the coordinate bond is weakened and re-forms with optimal conformations during the heating-cooling process, which stiffens the hydrogel network and suppress noradiative decay. This work proposes a reliable strategy for designing nonaromatic RTP hydrogels, and provides a hydrogel for multifunctional applications.