Facile Fabrication of Tough Hydrogels Physically Cross-Linked by Strong Cooperative Hydrogen Bonding

Abstract

Novel hydrogels with excellent mechanical properties have prompted applications in biomedical and other fields. The reported tough hydrogels are usually fabricated by complicated chemical and/or physical methods. To develop more facile fabrication methods is very important for the practical applications of tough hydrogels. We report a very simple yet novel method for fabricating tough hydrogels that are totally physically cross-linked by cooperative hydrogen bonding between a pre-existing polymer and an in situ polymerized polymer. In this work, tough hydrogels are prepared by heating aqueous acrylamide (AAm) solution in the presence of poly(Nvinylpyrrolidone) (PVP) but without any chemical initiators or covalent bonding cross-linking agents. Mechanical tests of the asprepared and swollen PVP-in situ-PAAm hydrogels show that they exhibit very high tensile strengths, high tensile extensibility, high compressive strengths, and low moduli. Comparative synthesis experiments, DSC characterization, and molecular modeling indicate that the formation of strong cooperative hydrogen bonding between the pre-existing PVP and the in situ formed PAAm chains contributes to the gel formation and the toughening of the hydrogels. The unique microstructure of the gels with evenly distributed flexible cross-linking sites and long polymer chains attached to them endow the hydrogels with an excellent mechanism of distributing the applied load.

Supramolecular Polymer Networks: Preparation, Properties, and Potential

“…Recently, Song and coworkers reported a very simple new method for fabricating tough hydrogels that are physically cross-linked by cooperative hydrogen bonding between a preexisting polymer and an in situ polymerized polymer [158]. These hydrogels were prepared by heating an aqueous acrylamide (AAm) solution in the presence of poly(N-vinylpyrrolidone) without any chemical initiators or covalent-cross-linking agents.…”

Radical Chain Polymerization Catalyzed by Graphene Oxide and Cooperative Hydrogen Bonding

“…[ 26 ] Moreover, the addition of GO leads to easier occurrence of polymerization for AA, as indicated by the lower onset temperatures for the AA/ PVP/GO system (28.1 °C), with comparison to 35.5 °C for the AA/PVP system ( Figure 1 a,b; Figure S2, Supporting Information). The onset temperature for the AA/PVP/GO system is also lower than that of AA/GO (32.6 °C).…”

Injectable scaffolds: Preparation and application in dental and craniofacial regeneration

“…Recently, a double hydrogen bonding hydrogel was reported to exhibit elevated tensile and compressive strengths over a broad pH range [102]. Furthermore, a novel fabrication method was developed to synthesize a tough hydrogen bond, crosslinked hydrogel without any chemical initiators or covalent bonding crosslinking agents by copolymerizing poly( N -vinylpyrrolidone) and acrylamide [103]. …”