Photodegradation of St-MMA Copolymers: Correlation of Degradation, Styrene Content,and Photophysics

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Polymers and High Performance Materials


A series of styrene(St)-methyl methacrylate(MMA) copolymers with compositions ranging from 0 to 100% St were synthesized and exposed to UV light for various periods of time. The changes in yellowing (yellowness index-YI) and absorbance of exposed films were evaluated as a function of photolysis time and St content. Both the changes in YI and absorbance at 400 nm were found to increase dramatically for polymer films with styrene (St) content greater than about 50%. A direct correlation between increases in the YI and absorbance at 400 nm with mean styrene sequence length was found with a maximum change being obtained for copolymers with mean sequence length of approximately 5 St units or greater. A small absorbance shoulder at 270-290 nm was observed for copolymers with St content less than 30% after relatively short irradiation times (e.g. 2 hours). Excimer formation of copolymers in dilute solution was found to increase with an increase in St content and St sequence length; in films, a plateau in the relative excimer emission was attained with a St content of 60%, corresponding to a mean St sequence length of 2.

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Journal of Macromolecular Science: Pure and Applied Chemistry





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