Fabrication of a novel polydiacetylene-based gel system through self-assembly and the stimuli-induced colorimetric responsiveness

The gel provides a wonderful platform for the study of functional polymer properties in the soft matter state. Here in this work, a novel molecular gel was readily prepared through the self-assembly of isophthalic acid substituted diacetylene derivative in mixed DMF/H₂O solvents. Upon UV irradiation, conjugated polydiacetylene (PDA) in blue phase was successfully generated in the molecular gel form by 1,4-addition topopolymerization. This PDA-based molecular gel illustrated a reversible blue-purple-red chromatic transition in response to heating, thus demonstrating a good thermal stability. The incorporation of carboxyl groups into PDA provided this molecular gel the ability to make a distinction between acidic and alkaline environments. In specific, when the PDA molecular gel was exposed to acidic environment, no obvious color change could be observed. However, when it was exposed to alkaline aqueous solution or atmosphere, a clear blue-to-red colorimetric responsive behavior took place within a short time. More interestingly, ten commonly used organic solvents were tested on this molecular gel, and the blue PDA turned into red phase only in the case of triethylamine, thus suggesting a great prospect for selective recognition by naked eyes.