Conventional Radical and RAFT Alternating Copolymerizations of Hydroxyalkyl Vinyl Ethers and Dialkyl Maleates.

The alternating copolymerization of hydroxyalkyl vinyl ethers and dialkyl maleates is investigated by conventional radical polymerization and reversible addition-fragmentation chain transfer polymerization (RAFT). The influence of comonomer structure, comonomer feeding ratios, and monomer concentrations on the copolymerization and the copolymer structure have been investigated systematically. With 2-hydroxyethyl vinyl ether (HEVE) and dimethyl maleates (DMM) as comonomers, a well-defined alternating copolymer is prepared with Mn=3400 and Mw/Mn=1.93 up to 71.6% monomer. The alternating sequential chain structure of the copolymers has been proved by both NMR and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The experimental reactivity ratios and theoretical calculated highest occupied molecular orbital and the lowest unoccupied molecular orbital of vinyl ethers and alkyl maleates support that these monomer pairs have tendency to form alternating copolymers. With 2-cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)carbamodithioate as the RAFT agent, the molecular weight of HEVE and DMM copolymer increases with the monomer conversion, demonstrating a controlled radical polymerization feature with well-controlled molecular weight and relatively narrower molecular weight distribution. With alternating copolymer of HEVE and DMM as macro-CTA (Mn=5200 and Mw/Mn=1.46), both the chain extension with HEVE and DMM (Mn=10400 and Mw/Mn=1.72) and block copolymerization with vinyl acetate have been successfully achieved (Mn=8500 and Mw/Mn=1.52). [ABSTRACT FROM AUTHOR]