Post‐Salting‐Out Polymerization Enriching Dynamic Crosslinks for Ultralong High‐Temperature Phosphorescence Hydrogels

Room-temperature phosphorescence (RTP) and high-temperature phosphorescence (HTP) polymer hydrogels hold great photonic applications in 3D printing, bioimaging, etc. Unfortunately, the soft, wet nature of hydrogels fundamentally contradicts the stringent confinement requirements for efficient phosphorescence, making the RTP hydrogels with tens-of-seconds afterglow remain underdeveloped, while there is still no report of HTP hydrogels. Herein, we propose a post-salting-out polymerization strategy to significantly enrich the dynamic crosslinking network for the compact confinement of HOF-protected luminogens, leading to remarkable RTP and especially ultralong HTP of hydrogels. Such dynamic hydrogen bonds-assisted crystallization enhancement synergizes with the orderly HOF structure to significantly restrict molecular vibrations around luminogens and isolate water/oxygen. Consequently, unprecedented RTP lifetime (∼3.3 s) and afterglow (∼45 s) are achieved in hydrogels for the first time. Owing to the good thermo-stability of HOF and crystallization structures, their HTP lifetime and afterglow are still found to be above 1.3 s and 30 s, even at 100°C, despite the fact that the hydrogen bonds between polymers and HOF rosettes are sensitive to high temperature. Multicolor RTP and HTP performances are further demonstrated by either varying the luminogens or doping commercial dyes into the hydrogel matrix. This study opens new avenues for ultralong HTP hydrogels to broaden their applications.