PHOTODEGRADATION OF HIGH POLYMERS IN SOLUTION. PART IV. THE EFFECT OF ADDITIVES ON THE PHOTOLYSIS OF POLY(METHYL METHACRYLATE).
NAVAL RESEARCH LAB WASHINGTON D C
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Polymethyl methacrylate was photolyzed by 2537A radiation at room temperatures in methylene chloride and in dioxane. The quantum yields for random scission in the absence of air in dioxane were 0.168 scissionquantum absorbed at an intensity absorbed by the polymer of 0.30 X 10 to the 16th power quantaml-min in methylene chloride the corresponding data are 0.149 and 0.27 x 10 to the 16th power. The quantum yields in the presence of air are about half these yields. A wide variety of chemical additives in the polymer solutions were sensitizers or inhibitors of degradation. The strongest inhibitors were those additives whose lowest excited triplet levels were below about 23,000cm, and the sensitizers were those additives whose lowest excited triplet levels were above 27,000cm. By postulating electronic energy transfer via the lowest excited triplet levels as the mechanism for inhibition or sensitization a triplet is inferred for the polymer between 23,000 and 27,000cm. As further evidence of this postulate a number of nitro compounds which would be expected to form triplets were found to show promise as inhibitors to the polymethyl methacrylate photolysis. Author
- Radiation and Nuclear Chemistry