Photoresponsive supramolecular gels based on amphiphiles with azobenzene and maltose or polyethyleneglycol polar head

Abstract

In the context of exploring new materials based on low molecular weight amphiphiles, we prepared a new series of photoresponsive gelators with azobenzene as photosensitive unit, D-maltose or poly(ethylene glycol) (PEG) as polar head, and L-phenylalanine as linker. The gelation properties of the final amphiphiles and the intermediate molecules have been studied in different solvents. Organogels are obtained for all of them, except for compound with PEG₁₆ polar head. Gelation in polar solvents, as DMSO, was achieved. The morphology of supramolecular structures was characterized by electronic microscopy. The chiro-optical properties of gels, due to the supramolecular chirality imposed by the molecular chirality, were also studied. The modifications under irradiation have been monitored by UV-visible spectroscopy and electronic circular dichroism (ECD). Two of the obtained materials showed a gel–sol transition by irradiation with UV light and further thermal cis–trans isomerization to gel state at room temperature.