Specific Polymerization Mechanism Involving β-Scission of Mid-Chain Radical Yielding Oligomers in the Free-Radical Polymerization of Vinyl Ethers

Abstract

Butyl vinyl ether (BVE) was polymerized radically, and the resultant oligomeric poly(BVE)s were characterized mainly using MALDI-TOF-MS spectrometry. For a further structural identification, the poly(BVE) obtained in bulk was subsequently subjected to 1H NMR measurement. Notably, an intensive peak assignable to −CH2C(═O)CH2− protons was observed unexpectedly although a peak assignable to −CHO proton as the terminal end-group generated via β-scission of growing polymer radical as a presumed chain-end forming reaction appeared only weakly. Thus, a plausible chain-end forming reaction would be the intramolecular (backbiting) hydrogen abstraction to form mid-chain radical which subsequently undergoes β-scission resulting in oligomeric poly(BVE) with carbonyl group in the polymer backbone. Then, the specific polymerization mechanism involving β-scission of mid-chain radical yielding oligomers is discussed. The hydrogen abstraction ability of growing poly(BVE) radical was checked by using toluene as a solvent h...