A nonionic photoresponsive surfactant has been developed which incorporates the light-sensitive azobenzene group into its tail.  Cis-trans photo-isomerization of this group changes the ability of the surfactant to pack into aggregates in solution or into adsorbed monolayers at interfaces, allowing for surface and bulk properties to be modified by varying illumination conditions.  NMR studies indicate that a solution removed from light for an extended period of time consists almost entirely of the trans isomer, while samples exposed to light of fixed wavelength eventually reach a photostationary state containing significant amounts of both isomers, with UV illumination producing a mixture dominated by the cis isomer.  Fluorescence measurements have been used to determine the CMC of the surfactant under different illumination conditions (dark, visible light, UV) and the results suggest segregation of the two isomers into different aggregate phases. Micelles or vesicles rich in the trans isomer form once a critical amount of trans is reached, while a cis-rich bicontinuous phase is formed at a larger critical cis concentration. TEM studies performed previously on this system demonstrate the differences in the aggregate structure under different illumination conditions at high concentrations. The dynamic surface tension profiles of this surfactant under the different illumination conditions are profoundly different from each other despite reaching the same equilibrium tension in measurements performed at concentrations well above the CMC. This equilibrium presumably corresponds to a surface saturated with the trans (more surface active) isomer. After creation of a fresh interface, the dark-adapted sample shows a single relaxation in surface tension, while mixtures containing cis surfactant exhibit a more rapid initial decrease in tension, followed by a plateau of nearly constant tension, and end with a second relaxation to equilibrium.  This behavior suggests competitive adsorption between the cis and trans isomers present in the mixtures, in which the cis isomer reaches the interface more quickly and initially dominates the surface, causing the intermediate tension plateau, before ultimately being displaced by the trans isomer.  Among the isomeric mixtures, the rapidity of the initial decline in surface tension and the duration of the intermediate plateau are both found to increase with increasing cis content.  Surface pressure measurements of adsorbed monolayers of the surfactant under the various illumination conditions were made using a Langmuir film balance, and the resulting pressure-area isotherms are found to vary between the different isomeric compositions, with saturation pressures which lend support to the competitive adsorption hypothesis. Diffusion models were developed to estimate the time scales expected for surfactant adsorption and surface tension relaxation in these systems.  These models account for the role of aggregates in the adsorption process, and consider limiting behavior for three aggregate properties: mobility, dissolution rate, and ability to incorporate into the interface.  Good agreement is found between the model predictions and the experimentally observed relaxation time scales, though the results are inconclusive regarding the exact role of aggregates.