Near-monodisperse, catalytically active, imidazole-containing homooligomers: Synthesis by group transfer polymerization and solution characterization

Abstract

Oligomers covering degrees of polymerization up to 23 of 2-(1-imidazolyl)-ethyl methacrylate (ImEMA) were synthesized by group transfer polymerization (GTP) in propylene carbonate and tetrahydrofuran (THF). While GTP proceeds smoothly in propylene carbonate, polymerization in THF is accompanied by oligomer precipitation. The molecular weights (MWs) and molecular weight distributions (MWDs) of the oligomers were obtained by gel permeation chromatography (GPC) using acidic aqueous sodium nitrate as the eluent. Good control over the MW and small polydispersity indices (PDIs) were measured for the oligomers prepared in propylene carbonate but not in THF. The oligomers were evaluated for their ability to hydrolyze 4-nitrophenyl acetate in aqueous solution. The hydrolytic activity increased with oligomer MW. The oligomer concentration- and substrate concentration-dependencies of the initial hydrolysis rate were both found to be approximately first order. The hydrolytic activity increased with an increase in pH, manifesting the enhanced nucleophilicity and pronounced hydrophobicity of the unprotonated form of the repeating units.