A high strength pH responsive supramolecular copolymer hydrogel

Constructing high strength pH sensitive supramolecular polymer hydrogel remains very challenging due to the unavoidable network swelling caused by ionization of acid or basic groups at a specified pH. In this work, we proposed a simple and very convenient approach to fabricate high strength pH responsive supramolecular polymer (SP) hydrogels by one-pot copolymerization of N-acryloyl glycinamide (NAGA) and 2-vinyl-4,6-diamino-1,3,5-triazine (VDT), two feature hydrogen bonding monomers. In these PNAGA-PVDT SP hydrogels obtained, the hydrogen bonding of NAGA was shown to play a dominant role in reinforcing strength, while the hydrogen bonding of diaminotriazine served as a pH sensitive moiety. At pH 3, the mechanical properties of PNAGA-PVDT hydrogels decreased to a different extent due to the breakup of hydrogen bonding; in contrast, the hydrogel resumed the original strength while pH was raised to 7.4 because of reconstruction of hydrogen bonding. Over the selected pH range, the PNAGA-PVDT hydrogels exhibited up to 1.25 MPa tensile strength, 845% breaking strain, 69 kPa Young's modulus and 21 MPa compressive strength. This novel high strength pH-responsive SP hydrogels may find applications in biomedical and industrial fields.