(153e) Effect of Solvent On Polymer Chain Length and Chain-Transfer Reactions in Self-Initiated High-Temperature Polymerization of Methyl Acrylate

High-temperature (> 100 oC) polymerization of alkyl acrylates was found to produce low molecular weight, high functional acrylic resins in the absence of any added extraneous initiators . While studies using mass spectrometry and nuclear magnetic resonance spectroscopy were unable to determine the mechanism of initiation , radical formation via chain-transfer reactions such as backbiting and β-scission was postulated . More recently, quantum chemical studies demonstrated that monomer self-initiation is the most likely mechanism of initiation in spontaneous high temperature polymerization of alkyl acrylates . Validation of this mechanism was provided by fitting calculated structures upon mass spectrums from analysis of methyl acrylate polymer samples via matrix assisted laser desorption/ionization time of flight (MALDI-TOF), and ethyl and n-butyl acrylate polymers using electronspray ionization (ESI)-Fourier transform mass spectrometry . Experimental studies of self-initiated polymerization of methyl and n-butyl acrylate have indicated that solvent type (polar or non-polar) can influence the rate of chain transfer and propagation reactions in self-initiated high-temperature polymerization of alkyl acrylates . However, no quantitative fundamental understanding of these solvent effects exists. In this study, for self-initiated polymerization of methyl acrylate, using B3LYP/6-31G*, we have investigated the influence of solvents such as xylene, cyclohexanone and DMSO on propagation and chain-transfer reactions, the effect of chain length on the energy barrier of these reactions and the highly probable mechanism of backbiting and β-scission for radical generation.