Mass Diffusion‐Dominated Phase Separation Enabling On‐Demand and Repeatable Lifetime Programming of Room‐Temperature Phosphorescence Polymer Hydrogels

Current luminescent polymer hydrogels rely primarily on tunable emission intensities/colors. Room-temperature phosphorescence (RTP) hydrogels with on-demand programmable lifetimes, albeit long envisaged, have never been achieved, but such RTP hydrogels will provide another lifetime dimension to enrich the family of stimuli-responsive materials for broadening their emerging applications. Herein, the mass diffusion-dominated phase separation strategy is proposed to develop the first RTP polymer hydrogels, whose lifetime can be continuously programmed from 9.1 to 130.8 ms. Upon heating at 90 °C, cooperative coordination and hydrophobic interactions in hydrogels induce a dense/sparse polymer phase separation, leading to controllable rubbery-to-glassy transition with 154-fold enhancement in Young's modulus, thereby efficiently restricting molecular vibrations and stabilizing triplet excitons. Note that the hydrogels' RTP performance is essentially not controlled by heat transport but is dominated by phase-separation kinetics, therefore their lifetimes can be widely programmed by merely manipulating the heating duration. Further natural cooling at 25 °C makes polymer phase re-fusion to recover the rubbery state, enabling the repeatable RTP lifetime programming. Based on these findings, rewritable spatiotemporal-resolved information decryption platform with time-dependent security is demonstrated. This study opens new avenues of RTP hydrogels by demonstrating the unprecedented lifetime-programming capacity and enriches the intelligence of luminescent materials.