A photochemically active thin-film composite membrane was made by the interfacial copolymerization of a mixture of 3-diazo-4-oxo-3,4-dihydro-1,6-naphthalene disulfonylchloride and naphthalene-1,3,6-trisulfonylchloride in CCl4 with aqueous 1,6-hexanediamine on the surface of a polysulfone ultrafiltration membrane. The chemical functionality of the resulting polysulfonamide membrane surface was modified via a photochemical reaction in the presence of various nucleophiles to form membranes containing bromoethyl ester, dioxolan, and hydroxyethyl ester functionality. Surface analysis techniques of attenuated total reflectance-FTIR, scanning electron microscopy (SEM), energy disperse spectral analyzer (SEM/EDS), and electron spectroscopy (ESCA) were used to confirm the changes in the chemistry of the thin-film composite membranes. Changes in chemistry, on irradiation, were also examined with model compounds. The reverse osmosis flux and separation of various solutes with these membranes are reported and discussed in terms of the photochemical modifications of the membrane surface.