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Photochemical grafting of acrylated azo dyes onto polymeric surfaces. V. Grafting of some acryloxy-substituted aromatic diazenes as model molecules onto polypropylene, polycaprolactam, and poly(ethylene terephthalate) films
No full textPhotochemical induced grafting (1) and graft polymerization (2) from N,N-dimethylformamide solutions of four acryloxy-substituted aromatic diazenes, chosen as model molecules of acryloxy azo dyes, were investigated kinetically at 25°C onto polypropylene, polycaprolactam, and poly(ethylene terephtalate) films, by polychromatic irradaition. Quantum efficiencies at zero concentration of dyes and lifetimes of excited states for processes (1) and (2) were evaluated from experimental data by Stern-Volmer plots. The surface density of grafted molecules at the end of process (1) was not affected by the concentration of dyes in solution, but varied sensibly with the chemical nature of polymers and dyes. The relevant parameters are discussed on the basis of the proposed mechanism
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. VI. Effect of 1,2-diphenyl-2,2-dimethoxyethanone as photoinitiator on the grafting of some acryloxy-substituted aromatic diazenes onto poly(propylene) and poly(caprolactam) fibres
No full textPhotochemical grafting of acrylated azo dyes onto polymeric surfaces. VI. Effect of 1,2-diphenyl-2,2-dimethoxyethanone as photoinitiator on the grafting of some acryloxy-substituted aromatic diazenes onto polypropylene and polycaprolactam fibres
No full textWith the wide variety of vinyl and other monomers available today, photochemical grafting may become an established technical method to impart desired surface characteristics: from antistatic 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. This presentation focuses attention on some photochemical processes for textile treatments, and for textile printing, particularly
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. III. Effect of wavelength on the grafting of some acryloxy-substituted aromatic diazenes onto polypropylene fibres
No full textKinetic studies of photochemically induced grafting (1) and graft polymerization (2) onto polypropylene fibres from N,N-dimethylformamide solutions of four acryloxy-substituted aromatic diazenes, chosen as model molecules of acrylated azo dyes, were carried out at 25°C by monochromatic irradiation at various wavelengths. The effect of dye concentration was systematically investigated, and quantum efficiencies at zero concentration of dyes, as well as lifetimes for process (1) and (2), were evaluated using Stern-Volmer plots. The marked influence of wavelength and the constancy of the relatively long lifetimes at the various wavelengths support the hypothesis that quantum yields reflect efficiencies of conversion from the states populated by light absorption to reactive upper triplets
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. II. Effect of wavelength on the grafting of 4-(N-ethyl-N-2-acryloxyethyl)amino-4'-nitroazobenzene onto polypropylene fibres
No full textQuantum Yields of grafting and graft-polymerization (ph1 and ph12, respectively) of 4(N-ethyl,N-2-acryloxyethyl-amino)-4'nitro azobenzene brought into contact with polypropylene fibres by evaporation of solvent from toluene solutions were determined as a function of wavelength. A kinetic investigation of the two processes was also carried out as a function of dye concentration with a polypropylene ribbon immersed in a n-hexane solution of the dye. the marked influence of wavelength, the pronounced effect of concentration quenching on both phi1 and phi2 and the constancy of the relatively long lifetimes calculated from the Stern-Volmer plot at various wavelengths support the hypothesis that phi1 and phi2 values reflect efficiencies of conversion from the states populated by light absorption to the reactive states. The behaviour of this system is dicussed in a more general framework of photochemical reactivity of compounds which have a carbonyl group and a conjugate double bond capable of twisting in an excited state to a non planar geometry,
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. I. Grafting of 4-(N-ethyl, N-2-acryloxyethyl) amino, 4′-nitro, azobenzene onto polyamide and polypropylene fibers
No full textIn the reported experiments, photochemically induced grafting and graft polymerization of 4-(N-ethyl, N-2-acryloxyethyl)amino, 4'-nitro, azobenzene(I), brought into contact with polyamide and polypropylene fibers by evaporation of solvent from toluene solutions, has been investigated kinetically at 45 degree C. Two constant-rate periods were observed. The first one was interpreted on the basis of an autosensitized grafting mechanism of monomeric or oligomeric species of (I), photochemically initiated by hydrogen abstraction from the polymer surface. This first step occurred at a rate dependent on the chemical nature of the substrate being faster for polyamide than for polypropylene by a factor of about 1. 25; it was followed by a brief induction period, after which a transient autoacceleration led to a second constant rate process, independent of the substrate. This latter step was explained as an autosensitized photochemically induced graft polymerization of (I) on the first grafted layer
PHOTORESPONSIVE MEMBRANES INCORPORATING 6-SUBSTITUTED 1',3',3'-TRIMETHYLSPIRO-(2H-1-BENZOPYRAN-2,2'-INDOLINES)
No full textPhotoresponsive membranes incorporating 6-X-1',3',3'-trimethylspiro-(2H-1-benzopyran-2,2'-indolines) (6-X-BIPS), with X equals H, OH, Br, NO2 and 1',3',3'-trimethylspiro-(2H-1-naphthopyran-2,2'-indoline) (NIPS), supported by cellulose 2,4-diacetate, have been prepared. Membrane potentials, while irradiated by visible and UV light alternatively, in a pH range between 0. 5 and 10, were found to depend not only on the photochemical equilibrium between 'closed' and 'open' forms of 6-X-BIPS, but also on pH. Isoelectric points of membranes, which substantially coincide with zero point charge of 6-X-BIPS, were found to be independent of X substituents
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. IV. Grafting of 4-(N-ethyl-N-2-acryloxyethyl)amino-4'-nitro-azobenzene onto cellulose
No full textPhotochemically induced grafting and graft-polymerization of 4-(N-ethyl-N-2-acryloxyethyl)amino-4'-nitro-azobenzene I, brought into contact in the solid state with cellulose by evaporation of solvent from monomer solutions, has been investigated kinetically at 30°C. Two constant rate periods were observed. The first one was interpreted on the basis of a self-sensitized grafting mechanism of monomeric or oligomeric species of I, photochemically initiated by hydrogen abstraction from the cellulose surface. The second one was explained as a self-sensitized photochemically induced graft-polymerization of I on the first grafted layer. Some particular features, such as concurrent photodegradation of the first grafted layer at low surface coverage, are discussed in the light of the proposed mechanism
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