Poly a-methylstyrene

Poly-a-methylstyrene and polymethylmethacrylate degradations show strong similarities. Thus, both polymers depolymerize at relatively low temperatures. Almost pure monomer is obtained as volatile product Depolymerization of polymethylmethacrylate, however, is initiated at unsaturated chain ends below 250°C, whereas poly-a-methylstyrene undergoes mainly random-chain scission. 

The degradation of poly-a-methylstyrene in solution was reinvestigated by Jellinek and Luh [84] with special emphasis on the effect of solvent 

The same mechanism was shown to be operative for films random initiation and depolymerization with 1/7 x or I/7 x [80, 81]. The kinetic chain length is, however, greater for solutions than for films at the same temperature. In view of the data obtained with solutions, diffusion of polymer radicals from cages has also to be considered for polymers in the bulk phase [84]. 

Photodegradation of poly(a-methylstyrene) (3.86) occurs by hydrogen abstraction from the methylene group and the formation of a polymer peroxy group  

This polymer peroxy radical can abstract hydrogen from the same and/or neighbouring polymer chain, and form polymer hydroperoxide  

The polymer peroxy radical may also participate in the chain scission reaction by the way of a six-membered ring transition state [1037]  

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