title: Self-assembled switching gels with multiresponsivity and chirality.
abstract: A multiresponsive hydrogel material consisting of a commercial cationic surfactant and an azobenzene derivative functionalized with four carboxylic acid groups was constructed. The achiral azobenzene molecule as a gelator produces chirality at the supramolecular level in the presence of H(+). The acid-induced gelation and morphology change of supramolecular gels were investigated in detail by cryogenic transmission electron microscopy (cryo-TEM), rheological measurements, circular dichroism (CD), and (1)H NMR spectra. Based on the results, a mechanism of the intermolecular H-bond-directed gelation and supramolecular chirality was proposed. Other than the pH sensitivity, the microstructure and the chirality of the hydrogel demonstrate reversible switching behavior in response to photoirradiation, on account of the photoisomerization of the azobenzene derivative. Accordingly, a chiroptical switch comprising four different states in response to pH and light stimuli is strategically constructed. Not only does the present system provide a good opportunity for investigating the gelation-induced supramolecular chirality by symmetry breaking totally based on achiral molecules, but it also proposes a new strategy to build multiresponsive supramolecular switches as particularly attractive for the future development of functional materials.
authors: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Ministry of Education, Shandong University , Jinan 250100, P. R. China.
authors: Wenrong
authors: W
authors: Zhao
authors: Dong
authors: D
authors: Wang
authors: Hongsheng
authors: H
authors: Lu
authors: Yangyang
authors: Y
authors: Wang
authors: Xuan
authors: X
authors: Sun
authors: Shuli
authors: S
authors: Dong
authors: Jingcheng
authors: J
authors: Hao
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000138:chemical synthesis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D015394:Molecular Structure; D010316:Particle Size; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D001391:Azo Compounds; D013501:Surface-Active Agents; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; C009850:azobenzene