ω-Iodinated poly(dimethylsiloxane) as a chain transfer agent in iodine transfer radical polymerization of vinyl acetate and dibutyl maleate: synthesis and structural characterization

Abstract

Iodine transfer radical homo- (ITP) and copolymerization (ITCP) of vinyl acetate (VAc) with dibutyl maleate (DBM) initiated by 2,2׳-azobis(isobutyronitrile) (AIBN) were performed in bulk at 80 °C in the presence of ω-iodo- terminated poly(dimethylsiloxane) (PDMS-I) as a macro-chain transfer agent (macro-CTA). 1H-NMR and gel permeation chromatography (GPC) results confirmed formation of the PDMS-b-PVAc diblock copolymer. Moreover, the results of 1H-NMR showed that the iodo-terminated chain ends are unstable and decompose to the aldehyde moieties. On the other hand, different behaviour was observed in the ITCP of the VAc and DBM. 1H-NMR and GPC results showed that presence of DBM in the reaction medium leads to degradation of the C-I bond of the PDMS-I, resulting in the generation of HI. In fact, PDMS-I acts as in situ generator of the CTA in the presence of DBM via reaction between the generated HI and VAc. In other words, it was found that P(VAc-co-DBM) copolymer chains are synthesised by ITP mechanism in the presence of in situ generated 1-iodoethyl acetate as a CTA. Therefore, a mixture of PDMS and P(VAc-co-DBM) chains was obtained.