Reverse iodine transfer polymerization of vinyl acetate and vinyl benzoate: synthesis and characterization of homo- and copolymers

摘要

Homo- and copolymers of vinyl esters including vinyl acetate (VAc) and vinyl benzoate (VBz) were synthesized via the reverse iodine transfer radical polymerization technique. Polymerization was carried out in the presence of iodine as the in situ generator of the transfer agent and 2,2-azobis(isobutyronitrile) as the initiator at 70 degrees C. Reverse iodine transfer radical homopolymerization of VAc and VBz led to conversions of 76 and 57%, number-average molecular weights of 8266 and 9814gmol(-1) and molecular weight distributions of 1.58 and 1.49, respectively. The microstructure of the synthesized polymers was investigated in detail using gel permeation chromatography, H-1 NMR, C-13 NMR and distortionless enhancement of polarization transfer (135 degrees decoupler pulse) techniques. Relatively narrow molecular weight distribution and controlled and predictable trend of molecular weight versus conversion were observed for the synthesized polymers, showing that reverse iodine transfer radical homo- and copolymerization of VAc and VBz proceeded with controlled characteristics. Results of molecular weight and its distribution along with the H-1 NMR spectra recorded for homo- and copolymers indicated that side reactions can occur during the course of polymerization with a significant contribution when VAc, even in a small amount, was present in the reaction mixture. This can result in polymer chains with aldehyde dead end and broadening of the molecular weight distribution. (c) 2015 Society of Chemical Industry