Surfactant aggregates hosting a photoresponsive amphiphile: structure and photoinduced conformational changes

This paper reports the aggregational and photoresponsive properties of aqueous solutions of a cationic bolaform surfactant, where an azobenzene moiety connects two identical hydrophobic chains terminated by quaternary ammonium groups. In analogy to common surfactants, the cationic bolaform molecules form supramolecular assemblies in water, and both interfacial and associative properties can be modulated and controlled by shining the sample with the appropriate wavelength radiation. Binary and ternary (BTHA/SDS/water) systems were investigated as a function of the photosurfactant concentration, sample composition and degree of irradiation. Structural properties of the supramolecular assemblies, obtained by QELS, SANS and cryo-TEM, have been correlated to the isomerization state of the surfactant, inferred from UV-vis spectroscopy.