Photoswitchable Surfactants–Are there Alternatives to Azobenzene-Based Systems?

Owing to their property to alter their surface-activity upon the irradiation with light, photoswitchable surfactants have gained tremendous interest in colloidal science. Their mere addition to a colloidal system allows, e. g., to obtain control over polyelectrolytes, micro- and nanoscale particles or emulsions. Most literature examples focus on azobenzene-based, or related, systems, which employ a photoisomerization reaction for switching. Other structures, such as spiropyrans, play a subordinate role, although they have gained increasing attention over the past few years. In this perspective article, we want to provide an overview about existing systems of photoswitchable surfactants. We address the issue that alternative photoswitches are given less attention, and what benefits surfactants could possess that are based on said switchable units. With our contribution, we want to broaden the view on stimuli-responsive surfactants – and to provide a guideline for the design of novel structures.