Synthesis of ion-conductive polymers by radical polymerization of deep eutectic monomers bearing quaternary ammonium groups with urea

Abstract

We describe the synthesis of three novel deep eutectic monomers (DEMs) by reacting cationic monomers bearing quaternary ammonium groups with urea. These DEMs can be used for the synthesis of ion-conductive polymers by radical polymerization. The reaction of methacroylcholine chloride (MC-Cl) with urea in a 1:2 M ratio at 80 °C for 1 h afforded the methacrylate-type DEM, MC-Cl-2Urea, as a transparent viscous liquid. Similarly, an acrylate- and a diallyl-type DEMs, ATMA-Cl-1Urea and DADMA-Cl-2Urea, were obtained through simple mixing of the quaternary-ammonium-containing monomers, 2-(acryloyloxy)ethyl trimethyl ammonium chloride (ATMA-Cl) and diallyl-dimethyl ammonium chloride (DADMA-Cl), respectively, with urea. Free radical polymerization of the DEMs afforded the corresponding polymers, which were characterized using NMR, viscosity, DSC, and TGA measurements. Among the three poly(DEM)s, the diallyl-type poly(DADMA-Cl-2Urea) exhibited the highest ionic conductivity of 5.3 × 10−3 S cm−1 at 25 °C under ambient humidity condition (relative humidity = 30–50%). The polymeric products obtained from liquid DADMA-Cl-2Urea via in situ polymerization without using any volatile organic solvent exhibited an ionic conductivity of 1.6 × 10−6 and 7.5 × 10−5 S cm−1 at 25 and 50 °C under anhydrous condition.