THIOHYDROXAMIC ESTERS - A NEW CLASS OF POLYMERIZATION REGULATOR

N-Hydroxypyridine-2-thione derivatives Ia-c and N-hydroxy-4-methylthiazole-2(3H)-thione derivatives IIa-b act as chain transfer agents in free radical polymerizations of methyl methacrylate (C(x) = 0.6-4.3), styrene (C(x) = 0.32-3.9), methyl acrylate (C(x) = 3.1-20), and vinyl acetate (C(x) = 9.7-80) at 60-degrees-C. Some retardation occurs with vinyl acetate and methyl acrylate. Ib also has the property of initiating the polymerization of methyl methacrylate photochemically, while IIb acts as a thermal initiator. The chain transfer constants of IIb make it particularly suitable for regulating molecular weight in batch polymerizations of methyl methacrylate and styrene.