The aromatic thionoester 3 (benzyl thionobenzoate) was an effective chain transfer agent in polymerizations of styrene ( C x = 1,0) and methyl acrylate ( C x = 1,2) at 60°C. This activity was close to the ideal for obtaining narrow molecular‐weight distributions in batch polymerizations. The thionoester 3 showed no activity in polymerizations of methyl methacrylate, but was too reactive to be useful in vinyl acetate polymerizations. Ring‐substituted thionoesters 9‐11 and 14 and 1 H NMR spectroscopy of the resulting polymers were used to establish the type and quantity of end‐groups. The thionoester 12 was used to produce low‐molecular‐weight polystyrene that was terminated at one end with a hydroxy group and at the other end by a thioloester moiety.
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Meijs et al. (1992) studied this question.