Aqueous and Non-Aqueous Synthesis of 2-(Dimethylamino)ethyl Methacrylate (Co)Polymers by Solution Radical Polymerization: Modeling and Experimental Study

Abstract

The radical polymerization kinetics of 2-(dimethylamino)ethyl methacrylate (DMAEMA) is explored in dimethyl sulfoxide, ethanol (EtOH), ethanol-water (EtOH/H₂O), and water. In situ nuclear magnetic resonance (NMR) spectroscopy is used to study both solvolysis and polymerization kinetics. Hydrolysis of nonionized DMAEMA occurs in H₂O and ethanolysis in EtOH/H₂O mixtures to form both methacrylic acid (MAA) and ethyl methacrylate (EMA), with the presence of water increasing the rate of ethanolysis in the mixed solvent. Although some solvolysis occurred in EtOH and EtOH/H₂O containing 25 wt.% H₂O, the rates are sufficiently low that essentially poly(DMAEMA) homopolymer is synthesized, unlike the DMAEMA/MAA copolymer formed in water and the DMAEMA/MAA/EMA terpolymer formed in water-rich EtOH/H₂O. A model is constructed to represent the polymerization of nonionized DMAEMA in solution, with the experimental results used to estimate key rate coefficients. The model predictions show good agreement with the experimental data on monomer conversion, average molar masses, and molar mass distributions. Similarly, the rate coefficients for polymerization of ionized DMAEMA are estimated based on experiments conducted in water at pH 1 and 4. The understanding gained from these studies is combined into a comprehensive mechanistic model to describe the polymerization of partially-ionized DMAEMA in the presence of hydrolysis.