Polydiacetylene (PDA) based supramolecular gel upon coassembly with a bolaamphiphilic cogelator

Supramolecular gel systems provide an ideal platform for the study of conjugated polydiacetylene (PDA) in soft materials. Compared with the well studied amphiphiles, the bolaamphiphilic molecules received much less attention in the fabrication of supramolecular gels. It's a big challenge to develop bolaamphiphilic type cogelators with reasonable molecular structures for the preparation of PDA supramolecular gels. Herein, a novel bolaamphiphilic cogelator containing an imidazole group at both ends was designed and coassembled with commercially available diacetylene acid monomer at 1:2 molar ratio by multiple non-covalent interactions. A white supramolecular gel was successfully prepared through the conventional heating-cooling method and systematically characterized by(1)H-NMR, FT-IR, XRD, SEM and rheology test. After UV irradiation, blue PDA was polymerized in the supramolecular gel system, as verified by UV-Vis absorption and Raman spectroscopy. When heated to 55 degrees C and 75 degrees C, a successive blue-to-purple-to-red colorimetric transition was observed for the PDA supramolecular gel. Interestingly, after cooled to room temperature, the purple PDA could return to the original blue phase reversibly, while the red PDA remained in the red phase with an obvious fluorescence enhancement effect. This work would promote the investigation of bolaamphiphilic molecules as well as conjugated PDA in soft materials.