Physicochemical and biological characterisation of azobenzene-containing photoswitchable surfactants

Surfactants are a versatile and widely used class of molecules, due to their valuable adsorption and self-assembly properties. In particular, surfactants that can respond to stimuli are of interest in modulating wetting, controlling delivery, and exploring mechanistic aspects of biological processes. Incorporating azobenzene into surfactants is a classic approach to rendering molecules that respond to light as an external stimulus; these molecules find wide utility in the precise spatiotemporal control of dispersed systems, from DNA to graphene. More recently, the creation of diverse libraries of such molecules has been achieved by coupling azobenzene-containing hydrophobic tail-groups to hydrophilic carbohydrate headgroups. Such a synthetic strategy offers fine control over adsorption and aggregation, as evidenced by physicochemical characterization of these molecules, uncovering rich phase behavior and diverse biological response. This article covers recent advances in the field of both 'traditional' and new azobenzene-containing photosurfactants, and offers directions for future study and use of this unique class of molecule.