Controlled/living radical polymerization of vinyl acetate by degenerative transfer with alkyl iodides

Controlled/living radical polymerization of vinyl acetate was achieved by a degenerative transfer process using alkyl iodides as transfer agents. Poly(vinyl acetate) with predetermined molecular weight and relatively low polydispersity was successfully synthesized. Methyl 2-iodopropionate and ethyl iodoacetate were employed as transfer agents, whereas 2,2'-azobis(isobutyronitrile) and alpha-cumyl peroxyneodecanoate were used as initiators. Methyl 2-iodopropionate and ethyl iodoacetate are both efficient transfer agents, yielding polymers with good agreement between theoretical and observed molecular weights up to M-n = 20 000 and low polydispersities (M-w/M-n < 1.5). In contrast, ethyl iodide was inefficient as a transfer agent, although it retarded polymerization. The influence of temperature and the concentrations of transfer agent and initiator were studied. The structure of poly(vinyl acetate) end groups was investigated using H-1 NMR. The iodo-terminated chain ends were unstable and decomposed to aldehyde moieties and subsequently to colored, conjugated structures. The progressive conversion of secondary to primary alkyl iodides chain end groups was observed, which is indicative of head-to-head addition.