The tough allograft adhesive behavior between polyacrylamide and poly(acrylic acid) hydrophobic association hydrogels

Polyacrylamide (PAAm) and polyacrylic acid (PAAc) hydrophobic association hydrogels were synthetized via free radical polymerization, respectively. Also, the hydrophobic alkyl groups were introduced into PAAm and PAAc to enhance the mechanical properties of hydrogels. It was found that PAAm and PAAc hydrophobic association hydrogels didn't exhibit any self-healing behaviors. When PAAm and PAAc samples were touched each other for a few seconds, however, PAAm hydrophobic association hydrogels exhibited a strong adhesive force with PAAc hydrophobic association hydrogels. Subsequently, the adhesive behavior between PAAm and PAAc hydrophobic association hydrogels was investigated. It indicated that the adhesion between PAAm and PAAc hydrophobic association hydrogels was based on hydrogen bonding between amide groups of PAAm and carboxyl groups of PAAc. Moreover, the hydrophobic groups also had the cooperative function to enhance the adhesive strength of PAAm/PAAc adhesive hydrogels via hydrophobic association. It was envisioned that more adhesive hydrogels would be developed in the future and more applications would be possibly achieved in repairing tissue engineering or interface.