A mechanically strong polyvinyl alcohol/poly(2-( N , N ′-dimethyl amino) ethyl methacrylate)-poly (acrylic acid) hydrogel with pH-responsiveness

Fabrication of a pH-responsive hydrogel with good mechanical strength is highly desirable in applications such as sensors and tissue engineering. In this work, a polyvinyl alcohol (PVA)/poly(2-( N , N ′-dimethyl amino) ethyl methacrylate) (PDMAEMA)-poly (acrylic acid) (PAAc) hydrogel was produced via a double-network (DN) protocol, in which PDMAEMA-PVA semi-interpenetrating hydrogel was constructed as the first network by the polymerization and crosslinking of PDMAEMA, and then AAc was polymerized in presence of the first network to form a polyion complexation as the second network. The DN PVA/PDMAEMA-PAAc hydrogel exhibited satisfactory mechanical strength which depended significantly on the crosslinking density of the first layer of the network. An optimal tensile strength of 0.45 MPa and compressive strength of 1.2 MPa can be obtained for DN hydrogel, and the compressive strength was 480% higher than that of the single-network hydrogel. The DN hydrogel also showed a pH-responsive swelling behavior and the equilibrium swelling ratio was controlled by both of the DMAEMA and AAc moieties in the network. Considering the wide potential applications of stimuli-responsive hydrogels, the present strategy is of highly practical value for broadening the application scope of the hydrogels.