Synthesis and properties of carrageenan-g-poly(sodium acrylateco- acrylamide) superabsorbent hydrogels

Novel biopolymer-based superabsorbent hydrogels were prepared by grafting poly(acrylic acid-coacrylamide)(PAA-co-PAM) chains onto kappa-carrageenan backbones through afree radical polymerizationmethod. The graft copolymerization reaction was carried out in a homogeneous medium and in the presenceof ammonium persulfate (APS) as an initiator and N,Nʹ-methylene bisacrylamide (MBA) as a crosslinker. Aproposed mechanism for hydrogel formation was suggested and the hydrogel structure was confirmed usingFTIR spectroscopy. The morphology of the samples was examined by scanning electron microscopy (SEM).The certain variables of the graft copolymerization (i. e. the monomer, the initiator, and the crosslinkerconcentration) were systematically optimized to achieve a hydrogel with maximum swelling capacity.Furthermore, the water absorbency of hydrogels was measured in solutions with pH ranged 1 to 13. Thecarrageenan-based hydrogel exhibited a pH-responsiveness character so that a swelling-deswelling pulsatilebehavior was recorded at pHs 2 and 8. Additionally, the swelling ratio in various salt solutions wasinvestigated in detail