Thermoresponsive Behaviors of Poly(<i>N</i>-methacryloyl glycinamide) and Poly(<i>N</i>-acryloyl glycinamide): Effect of Methacrylation

Poly(<i>N</i>-acryloyl glycinamide) (PNAGA) proves to be an interesting and useful polymer with an upper critical solution temperature (UCST) behavior in water due to intra- and intermolecular hydrogen bonding. Its methacrylamide counterpart, poly(<i>N</i>-methylacryloyl glycinamide) (PNMAGA), has a different UCST behavior, which is easier to dissolve in water. In this work, PNMAGA and PNAGA were synthesized by RAFT polymerization and free radical polymerization, and their solution properties in dilute aqueous media have been studied and compared in detail to elucidate the effects of temperature, polymer concentration, molecular weight, and chain end. The direct comparison provides a better understanding of the UCST behaviors. The presence of an extra methyl group on the repeating unit helps the polymer to dissolve better and eliminates the need for special thermal treatment to obtain a complete dissolution. Infrared spectroscopy and X-ray diffraction analysis show variation in hydrogen bonds between the two polymers and their respective monomers, providing insights into the structural origin of their different solution properties.