Polymer films, photosensitized oxidation

The photosensitized oxidations in solution for determination of ft by the slope-intercept method were carried out in a constant temperature bath with light from a 250-watt projector lamp with a UV-cutoff filter. Oxygen uptake was monitored with a conventional mercury burette. Polymer films also were irradiated with the same lamp containing a Coming CS 3-69 filter. 

A completely different approach to patterning conducting polymers involves the use of photosensitive oxidants [86,87]. In this process, a photosensitive oxidant is mixed with a host polymer such as poly (vinyl chloride), poly(vinyl alcohol), or polycarbonate. The composite is applied to a substrate. Upon irradiation of the film, the oxidant in the exposed regions is made inactive, whereas in the unexposed regions the oxidant can still induce polymerization of appropriate monomers. After exposure, the latent image is exposed to a monomer such as pyrrole either in solution or in the vapor state. Polymerization occurs only in the nonexposed areas where the oxidant is still active. In this fashion, patterns are delineated that consist of conducting composite materials. Some photosensitive oxidants include Fe(III) salts such as iron trichloride and ferrioxalate. Upon exposure, the Fe(III) is converted to Fe(II), which does not induce oxidative polymerization [86,87]. 

A novel polysiloxane, containing the isocyanide group pendent to the backbone, has been synthesized. It is observed to react with the metal vapors of chromium, iron and nickel to afford binary metal complexes of the type M(CN-[P])n, where n = 6, 5, 4 respectively, in which the polymer-attached isocyanide group provides the stabilization for the metal center. The product obtained from the reaction with Fe was found to be photosensitive yielding the Fe2(CN-[P])q species and extensive cross-linking of the polymer. The Cr and Ni products were able to be oxidized on exposure of thin films to the air, or electrochemically in the presence of an electron relay. The availability of different oxidation states for the metals in these new materials gives hope that novel redox-active polymers may be accessible. 

The photodegradation of unstabilized bisphenol A polycarbonate films is described as an autoaccelerating process initiated by formation of products arising from a formal photo-Fries reaction. Oxidation also contributes as an additional photodegradation pathway. Photosensitive polymers... 

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