Structure-Performance Relationships for Tail Substituted Zwitterionic Betaine-Azobenzene Surfactants

Azobenzene-containing surfactants (azo-surfactants) have garnered significant attention for their use in generating photoresponsive foams, interfaces, and colloidal systems. The photoresponsive behavior of azo-surfactants is driven by the conformational and electronic changes that occur when the azobenzene chromophore undergoes light-induced trans (sic) cis isomerization. Effective design of surfactants and targeting of their properties requires a robust understanding of how the azobenzene functionality interacts with surfactant structure and influences overall surfactant behavior. Herein, a library of tail substituted azo-surfactants were synthesized and studied to better understand how surfactant structure can be tailored to exploit the azobenzene photoswitch. This work shows that tail group structure (length and branching) has a profound influence on the critical micelle concentration of azo-surfactants and their properties once adsorbed to an air-water interface. Neutron scattering studies revealed the unique role that intermolecular pi-pi azobenzene interactions have on the self-assembly of azo-surfactants, and how the influence of these interactions can be tuned using tail group structure to target specific aqueous aggregate morphologies.

Automated summary

Azobenzene-containing surfactants have been widely studied for their use in generating photoresponsive systems. This research focuses on tail substituted azo-surfactants to understand how surfactant structure can be tailored for specific applications. The study reveals the significant influence of tail group structure and intermolecular pi-pi interactions on the behavior of azo-surfactants.