Evolved Gas Analysis of Polymethyl Methacrylate

The thermal decomposition of various types of polymethyl methacrylate under vacuum was investigated by evolved gas analysis with a mass spectrometer. Though the volatilized product is mainly methyl methacrylate due to unzipping, four steps of volatilization were observed, and decompositions depend on the molecular weight and the polymerization process. The mechanisms of these four steps are elucidated by comparison of the amount of the volatilized product found at each step with the molecular weight and the polymerization process. The first step is a depolymerization initiated at the weak bond of copolymerized oxygen, and the second and third steps consist of depolymerization initiated at the chain ends, which occur due to disproportionation in propagating radical termination during polymerization. The fourth and final step is a depolymerization initiated by random scission in the main chain. 27 ref.--AA