Synthesis, characterization and swelling behaviour of poly(acrylamide-co- methacrylic acid) grafted Gum ghatti based superabsorbent hydrogels

A mixture of acrylamide (AAm) and methacrylic acid (MAA) was crosslinked onto Gum ghatti (Gg) using N, N’-methylene-bis-acrylamide (MBA) as a crosslinker and ascorbic acid (ABC) and potassium persulphate (KPS) redox pair as an initiator. Optimized reaction parameters for the graft copolymerization of Gum ghatti with AAm were time (min)=90; temperature (C)=50; pH=7.0; deionized water (ml)=10; molar ratio of initiators (ABC:KPS mol:mol)=1:1; [AAm] (molL)=0.7746; [MBA] (molL)=0.0974. After that molar ratio of AAm-co-MAA keeping AAm as the principle monomer was optimized and was found to be 0.77+5.85 molL. Synthesized superabsorbent hydrogel was characterized by FTIR, SEM, TGA/DTA and XRD. Water absorption capacity of Gg-cl-poly(AAm-co-MAA) was investigated in deionized water and the polymer was found to show maximum swelling of 1312%. Effect of the ionic strength of various cations (Na, Ba, Fe and Sn) on Ps in different choride salt solutions (NaCl, BaCl2, FeCl3 and SnCl4) was studied. The hydrogel exhibited salt-sensitivity and cation exchange properties. pH responsive and on-off switching properties of the superabsorbing hydrogel was studied as well.