Scheme 1

A Free-radical polymerization of NAGA into PNAGA with initiators such as potassium persulfate (KPS) or the photoinitiator IRGACURE-2959. The polymer PNAGA formed hydrogen bonds in aqueous solution. B Preparation of PNAGA CNT inks and gels. In preparation Method 1, appropriate amounts of monomeric NAGA, KPS, and CNTs were polymerized into a soft and thermoreversible hydrogel by heating with the accelerator TEMED (4 wt%, Step I). Then, the gel was heated to 85 °C and loaded with 30 wt% additional NAGA monomer and photoinitiator (Step II). In Method 2, 4 wt% NAGA was photopolymerized into a soft and thermoreversible hydrogel (4 wt%, Step I). It was heated to 85 °C and loaded with 30 wt% added NAGA monomer, photoinitiator, and CNT to obtain the ink (Step II). After cooling, both inks were subjected to further UV photopolymerization to yield the PNAGA CNT hydrogels (Step III, A – D and A’ – D’, respectively)