Diazo transfer adjacent to a sulfoxide moiety to provide stable, isolable α-diazo-β-oxo sulfoxides has been achieved. Use of monocyclic and bicyclic sulfoxide precursors is critical in enabling isolation of stable derivatives, through introduction of conformational constraint, while acyclic α-diazo-β-oxo sulfoxides are too labile to isolate and characterize.
SynopsisProlonged heating at temperatures below 140°C. causes only slight changes in the properties of polysulfone. Exposure to ultraviolet light, however, results in substantial changes as evidenced by broad absorption in both the hydroxyl and carbonyl regions of the infrared spectrum, evolution of carbon monoxide and dioxide, decrease in polymer elongation and intrinsic viscosity, and pronounced yellowing. A freeradical mechanism is proposed in which chain scission occurs with the formation of low molecular weight, oxidized fragments as the predominant oxidation products.
SynopsisPolysulfone, polycarbonate, and phenoxy resins were aged under thermal and ultraviolet light conditions. Thermooxidative processes in polysulfone and polycarbonate are of such minor significance as not to impart noticeable losses in these materials below 125°C. I n phenoxy, however, thermal oxidation above 100°C results in rapid deterioration of all physical properties. This probably results from the low glass transition temperature of this polymer. Photo-oxidation rapidly degrades polysulfone. This appears to be a consequence of scission a t the sulfone link. In polycarbonate, however, the only serious result of short-term irradiation is discoloration. For phenoxy resin, crosslinking through reactions a t the hydroxyl group is the principal result of photooxidation. In all processes the bisphenol A portion of the three polymers appears to play only a small role.
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