The supramolecular polymer hydrogels feature self-healability, adjustable mechanical strength, and thermoplasticity, which are derived from the formation of supramolecular physical interactions in the hydrogel networks, such as H-bonding interactions, [6] host-guest interactions, [7] metal-ligand coordination interactions, [8] hydrophobic interactions, [9] multiple combined interactions. [10] Among them, H-bonds are generally weak noncovalent bonds, ubiquitous in biomolecules, but their synergistic interactions can reach a strength of the covalent bond; thus it is commonly utilized in designing supramolecular tough hydrogels. [11] Our previous study suggested that supramolecular polymer hydrogels based on single amide H-bonding interaction were unstable in water, [12] because the competitive solvation of H-bond donor and acceptor in polar solvents weakens its strengthening effect. [13] Inspired by the hydrogen-bonded clusters in the secondary structure of proteins, we constructed a supramolecular poly(N-acryloyl glycinamide) (PNAGA) hydrogel whose dual amide motifs in the side chain contributed to high strengths and outstanding antiswelling ability due to strong shielding of the hydrogen-bonded microdomains from water molecule attack. [12] By utilizing Type II photoinitiated self-condensing vinyl polymerization of N-acryloyl glycinamide (NAGA), the resultant hyperbranched PNAGA hydrogels demonstrated superior mechanical performances to those of linear PNAGA counterparts owing to the higher cross-linking density of H-bonds. [14] In addition, the H-bonding interactions of dual amide motifs could also be modulated by copolymerizing other monomers, [15][16][17][18] thus achieving the versatile hydrogels with mechanical properties spanning from high strength to soft injectability, which show promising applications as 3D printed osteochondral regeneration scaffold, [16] artificial vitreous body, [17] and postoperative antiadhesion barrier. [18] Our recent study revealed that only introducing one methyl group to the double bond of NAGA could lead to a considerable decrease in mechanical strengths and an increase in room temperature autonomous self-healability of the poly(N-methacryloyl glycinamide) hydrogels (MNAGA), which was resulted from the perturbation of one methyl substitution to H-bonds. [19] The intermolecular H-bonding density heavily influences the gelation and rheological behavior of hydrogen-bonded supramolecular polymer hydrogels, thus offering a delicate pathway to tailor their physicochemical properties for meeting a specific biomedical application. Herein, one methylene spacer between two amides in the side chain of N-acryloyl glycinamide (NAGA) is introduced to generate a variant monomer, N-acryloyl alaninamide (NAAA). Polymerization of NAAA in aqueous solution affords an unprecedented ultrasoft and highly swollen supramolecular polymer hydrogel due to weakened H-bonds caused by an extra methylene spacer, which is verified by variabletemperature Fourier transform infrared (FTIR) spectroscopy and s...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.