Poly(acrylamide‐co‐acrylic acid)/chitosan semi‐interpenetrating hydrogel for pressure sensor and controlled drug release

With high biocompatibility and pH‐sensitivity, hybrid hydrogels of chitosan (CS) have been widely used in sensor, drug release systems, adsorption, agriculture, and other fields. Herein, a poly(acrylamide‐co‐acrylic acid)/chitosan [P(AM‐co‐AA)/CS] hydrogel with semi‐interpenetrating (semi‐IPN) network was synthesized through in situ copolymerization of acrylamide (AM), N , N ′‐methylene‐bisacrylamide (MBAA) and acrylic acid (AA) solution of chitosan using potassium persulfate (KPS) and sodium bisulfite (SBS) as oxidation‐reduction co‐initiators. CS‐AA complex monomer was prepared by dissolving CS in AA solution. Meanwhile, MBAA was used as a crosslinker to enhance the strength of the resulted hybrid hydrogels via introducing chemical crosslinking to the substrate P(AM‐co‐AA) copolymer. The morphology of the freeze‐dried sample of P(AM‐co‐AA)/CS hydrogel shows dense interconnected pores. When the CS content is 2.4%, the P(AM‐co‐AA)/CS hydrogel has a compressive stress of 5.06 MPa at strain of 90.0% and a tensile strength of 161.71 kPa at strain of 1082.0%. The CP(AM‐co‐AA)/CS hydrogel also demonstrates extraordinary antifatigue property under cyclic compression of 85%. Because of the outstanding mechanical properties, a capacitive pressure sensor using P(AM‐co‐AA)/CS hydrogel as a dielectric with good durability and linearity at low operating voltage was fabricated. Besides, the water uptake of the P(AM‐co‐AA)/CS hydrogels is pH‐sensitive, and the hydrogels could serve as a matrix for loading of ranitidine hydrochloride with controlled release under different pH environments.