A dual stimuli responsive natural polymer based superabsorbent hydrogel engineered through a novel cross-linker

Natural protein-based polymers may serve as a potential source for developing advanced porous organic macromolecules, possessing exquisite control over the pores, which impart exceptional properties to these materials. Here, we describe a strategy to design, synthesize and develop an intelligent, dual stimuli responsive highly porous grafted polymer with exquisite control over the functionality of pores. The monomer 2-(4-((acrylamido)methyl)-1H-1,2,3-triazol-1-yl)-4-vinylbenzoic acid as a cross-linker, having pH responsive (acidic functional groups) and thermo-responsive (triazole and acrylamide groups) functional groups, was successfully prepared via click chemistry, for grafting onto the backbone of the natural polymer soy protein isolate (SPI) via microwave irradiation. Alkene groups were introduced at both the sides of the monomer, prior to grafting with SPI. Furthermore, to increase the hydrogen bonding network in the polymer, the pH responsive crosslinker 4-(4-hydroxyphenyl)butanoic acid (HPBA) was introduced while grafting. The grafted soy protein isolate polymer, SPI-g-[2-(4-((acrylamido)methyl)-1H-1,2,3-triazol-1-yl)-4-vinylbenzoicacid-co-4-(4-hydroxyphenyl) butanoic acid]-g-SPI, [SPI-g-(ATVBA-co-HPBA)-g-SPI], is characterized by using TGA for thermal stability, SEM and TEM for visual confirmation, NMR, LCMS and FTIR for grafting confirmation, XRD for crystallinity, MTT assay for cytotoxicity, and BET for analyzing the porous network structure. The size and morphological changes of [SPI-g-(ATVBA-co-HPBA)-g-SPI] are studied under different parameters for its potential use as an advanced porous macromolecule based superabsorbent polymer (SAP).