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

Monday, November 8, 2010: 4:40 PM
151 A/B Room (Salt Palace Convention Center)
Sriraj Srinivasan1, Nazanin Moghaddam2, Masoud Soroush2, Michael C. Grady3 and Andrew M. Rappe1, (1)Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA, (2)Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA, (3)DuPont, Wilmington, DE

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.

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