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Zinc powder-alkyl halide: a radical initiation system for living/controlled polymerization of vinyl monomers

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journal contribution
posted on 2014-10-27, 08:23 authored by Gokhan Cankaya, Niyazi Bicak

An initiation system comprising activated zinc powder and alkyl bromide is presented for polymerization of vinyl monomers, including vinyl acetate (VAc). The polymerization was demonstrated to be effected in dry conditions at 70 °C and very sensitive to moisture. A radical mechanism was evidenced by spin-trapping method using TEMPO as capping agent and followed block copolymer formation. First order kinetics with respect to concentration of the monomers, methylmethacrylate(MMA), styrene and VAc, relatively long induction periods, and moderate polydispersities (PDI: 1.6–2.4) were determined as typical characteristics of the polymerization system in bulk conditions. The polymerization system was demonstrated to be living, as evidenced by chain extension of the poly (vinyl acetate) (PVAc) with MMA. A ZnBr radical fragment was proposed as key intermediate controlling the chain growth by reversible combination with the active chain ends. The system was also combined with typical copper-mediated atom transfer radical polymerization (ATRP), in which ATRP-growth polystyrene (PS) was directly used as macroinitiator to initiate VAc polymerization yielding block copolymer.