Hydrophilic and hydrophobic copolymer systems based on acrylic derivatives of pyrrolidone and pyrrolidine

This article deals with the synthesis of hydrophilic methacrylic monomers derived from ethyl pyrrolidone [2-ethyl-(2-pyrrolidone) methacrylate (EPM)] and ethyl pyrrolidine [2-ethyl-(2-pyrrolidine) methacrylate (EPyM)] and their respective homopolymers. For the determination of their reactivity in radical copolymerization reactions, both monomers were copolymerized with methyl methacrylate (MMA), the reactivity ratios being calculated by the application of linear and nonlinear mathematical methods. EPM and MMA had ratios of r(EPM) = 1.11 and r(MMA) = 0.76, and this indicated that EPM with MMA had a higher reactivity in radical copolymerization processes than vinyl pyrrolidone (VP; r(VP) = 0.005 and r(MMA) = 4.7). EPyM and MMA had reactivity ratios of r(EPyM) = 1.31 and r(MMA) = 0.92, and this implied, as for the EPM-MMA copolymers, a tendency to form random or Bernoullian copolymers. The glass-transition temperatures of the prepared copolymers were determinedd by differential scanning calorimetry (DSC) and were found to adjust to the Fox equation. Total-conversion copolymers were prepared, and their behavior in aqueous media was found to be dependent on the copolymer composition. The swelling kinetics of the copolymers followed water transport mechanism case II, which is the most desirable kinetic behavior for a swelling controlled-release material. Finally, the different states of water in the hydrogels-nonfreezing water, freezing bound water, and unbound freezing water-were determined by DSC and found to be dependent on the hydrophilic and hydrophobic units of the copolymers. (C) 2002 Wiley Periodicals, Inc.