The effects of solvent and concentration on scission of polymers such as poly(methyl methacrylate) (PMMA) and polystyrene (PSt) in solution by high-speed stirring were investigated. Solvents were chloroform (good), benzene (intermediate), and ethyl acetate (poor) for PMMA and methyl ethyl ketone (good), toluene (intermediate) and dioxane (poor) for PSt, respectively. Concentration was varied from 0.04 to 2% w/v. The rate of scission of polymer chains was higher and the final molecular weight was lower in a good solvent than in a poor solvent at a low concentration for both polymers, but vice versa at a high concentration except for PSt in methyl ethyl ketone. Concentration dependence of the scission was large in a good solvent but small in a poor one. Polymer chains were ruptured to lower molecular weights with decreasing concentration, regardless of kind of polymer and solvent, showing that they were more easily broken in the isolated state.
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Nakano et al. (1975) studied this question.