Seba Calgari

Photoresponsive membranes incorporating 6-nitro, 1′,3′,3′-trimethylspiro-(2H-1-benzopyran-2,2′-indoline)

Abstract Photoresponsive heterogeneous membranes incorporating 6-nitro,1′,3′,3′-trimethylspiro-(2 H -1-benzopyran-2,2′-indoline) (6-NO2-BIPS), supported by cellulose 2,4-diacetate have been prepared. Membrane potential, measured in 10−2 and 10−4 m KCl, in a pH range between 2·0 and 8·5, while irradiating with visible and UV light alternatively, was found to depend not only on the photochemical equilibrium between ‘closed’ and ‘open’ forms of 6-NO2-BIPS, but also on pH. Charge density in the membrane, which is responsible for the potential signal and depends on pH, never reached values high enough to generate a Nernstian response. Fixed charge concentration values under UV irradiation, at different loadings of 6-NO2-BIPS in the membrane, were estimated by comparing experimental and theoretical curves, the latter at various combinations of the relevant parameters. Experimental behaviour was found to be consistent with the acid-base properties of 6-NO2-BIPS, and also with the shift, induced by pH, in the low pH range, of the tautomeric equilibrium between the protonated ‘open’ forms of 6-NO2-BIPS.

Photochemical Grafting of Acrylated Azo Dyes onto Polymeric Surfaces VI. Effect of 1,2-Diphenyl, 2,2-Dimethoxy, Ethanone as Photoinitiator on the Grafting of Some Acryloxy-Substituted Aromatic Diazenes onto Poly(Propylene) and Poly(Caprolactam) Fibers

Photo-induced grafting and graft polymerization onto polymers promise to become an elegant and powerful method for modifying surface properties. With the wide variety of vinyl and other monomers available today, photochemical grafting may become an established technical method to impart desired surface characteristics: from anti-static behavior to thermal stability, from adhesion to bacteriocidal properties, from water repellency to hygroscopicity, from soil resistance to flame retardant properties, from optical imaging to dyeability and so on. Photochemistry may consequently play a very important role in this field, by promoting knowledge, by studying applications, as well as optimizing conditions of industrial processes, potentially capable of being developed.