Photo-responsive azobenzene-based surfactants as fast-phototuning foam switch synthesized via thiol-ene click chemistry

Abstract

Stimuli-responsive surfactants especially azobenzene-containing with switchable molecular structures and surface properties offer tremendous applications in materials science and organic chemistry. Facile synthesis of the azo-surfactants with controllable structures continues to be fascinating as well as challenging. Herein, we present a simple and versatile click chemistry approach to synthesize a series of azo-surfactants with variable substituents via the simple thiol-ene click reaction. The structure and the photo-responsive properties of the azo-surfactants are characterized. These azo-surfactants exhibit rapid trans/cis photo-isomerization (within tens of seconds), and excellent reversible trans/cis/trans cycling stability (＞20 cycles) along with photo-tunable surface properties (e.g., critical micelle concentration and surface tension) via light irradiation. More importantly, utilized as the photo-tuning foam switch, a fast collapse of the azo-foams is observed with the defoaming time only a few minutes under UV light stimulation. As-formed azo-surfactant foams present high photo-sensitivity, making them very attractive in applications of green textile, oil extraction and emulsification.