Ultra-Low Doping of Frozen/Thawed Polyvinyl Alcohol Ionogels With Benzimidazole-Linked 2D Polymer Nanosheets for Enhanced Photoluminescence

Applying a nonchemical approach of polymer crystallizing for altering micro-conformations of a nonconjugated linear polymer can promisingly achieve enhanced photoluminescence without sacrificing mechanical properties of the matrix. Herein, to pursue an excellent nucleating agent for tuning the crystallization micro-conformation, a new type of two-dimensional polymer nanosheet (2DP) with benzimidazole-linked structure, with high specific surface area and unique shape morphology, was synthesized for frozen/thawed (F/T) polyvinyl alcohol (PVA)-based ionogel, which could provide an efficient way to significantly enhance the fluorescence of PVA by inducing crystalline conformation without changing chain topology. Notably, incorporating a mere ~0.05 wt.% of 2DP elevated the quantum yield of the PVA ionogel from 9.2% to an impressive 85.7%. Besides, at a higher 2DP doping of ~0.7 wt.%, a distinct afterglow effect originating from 2DP was also observed. It was revealed for the first time that the F/T cycle during the preparation of the PVA ionogel could effectively increase the photoluminescent intensity, mainly ascribed to PVA but not 2DP. The fluorescence enhancement within the ionogel could be predicted by quantum chemistry calculations and a deep learning model. This new ionogel shows great potential as smart luminescent polymer for flexible lampshade.