MEASUREMENT OF EFFECTS OF MIXING OF CHAIN CENTERS IN A NONUNIFORMLY INITIATED PHOTOPOLYMERIZATION

Apparatus has been developed for the study of effects of mixing of chain centers in nonuniformly initiated photoreactions. The experimental method is based on the use of a quartz reaction vessel, partially illuminated with ultraviolet light, equipped with a stirrer, and outfitted otherwise as a dilatometer. In preliminary experiments involving the direct photoinitiated bulk polymerization of methyl methacrylate, the rate of polymerization varied with stirring speed, effective optical thickness, and incident intensity approximately in accordance with theoretical predictions. Evidence was found for the presence of spurious initiators, and for a hysteresis effect, resembling the result of the compounding of effects of viscosity and mixing. Methods of overcoming these difficulties were suggested. © 1969, American Chemical Society. All rights reserved.