Poly(N-acryloyl glycinamide): a fascinating polymer that exhibits a range of properties from UCST to high-strength hydrogels

It has been fifty-four years since the N-acryloyl glycinamide (NAGA) monomer and its polymer (PNAGA) were first reported (in 1964). Over the past decades, PNAGA aqueous solution systems within a broad concentration range have been prepared and significantly distinct performances have been observed. This feature article is aimed toward introducing the representative properties (aggregation, UCST-type phase separation, the thermoreversible sol double left right arrow gel transition behaviors and the high mechanical properties) of PNAGA aqueous systems with three concentration regions (low, medium and high concentration). In particular, the fabrication of dual-amide hydrogen bonding reinforced high-strength supramolecular polymer hydrogels and the relevant biomedical applications are highlighted. The potential challenges, as well as the future prospects of the PNAGAs, are also indicated.