One-pot synthesis of soy protein (SP)-poly(acrylic acid) (PAA) superabsorbent hydrogels via facile preparation of SP macromonomer

A soy protein (SP)-poly(acrylic acid) (PAA) superabsorbent hydrogel was synthesized from soy protein isolate and potassium acrylate. Alkali-treated SP was turned into macromonomer through the functionalization of its primary amine groups using methacrylic anhydride. The SP-PAA hydrogel was formed by free radical copolymerization of the SP macromonomer and potassium acrylate monomer. It was demonstrated that the SP macromonomer acted as a macro-crosslinker and no additional crosslinker was needed. The whole synthesis was Conducted in a one-pot process. The chemical structure and degree of functionalization of the SP macromonomer were characterized by H-1 NMR spectroscopy and UV-vis spectrophotometry, respectively. The SP to acrylic acid weight ratio at the preparation of the hydro gel was 1/3 and the SP content in the final product was 11-19%. As a result of the functionalization of SP, compressive gel strength was significantly improved, gel content was increased and extractable SP was reduced. Free swelling in distilled water was reduced for SP macromonomer gels due to increased crosslink density. The SP-PAA hydrogels displayed a stable swelling performance in buffer solutions with pH ranging from 6 to 11.5. (C) 2017 Elsevier B.V. All rights reserved.