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 ⇔ 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.