title: Modified carrageenan. 2. Hydrolyzed crosslinked kappa-carrageenan-g-PAAm as a novel smart superabsorbent hydrogel with low salt sensitivity.
abstract: A novel pH-responsive superabsorbing hydrogel based on K-carrageenan (kappaC) was prepared through polyacrylamide crosslinking grafting followed by alkaline hydrolysis. The hydrogel structure was confirmed using FT-IR spectroscopy. The hydrolysis conditions were systematically optimized to obtain a hydrogel with maximum swelling capacity. Thus, the reaction variables, including the hydrolysis time and temperature, concentration of sodium hydroxide, amount of hydrogel hydrolyzed and post-neutralization pH, were optimized. The swelling measurements of the hydrogels were conducted in 0.15 M aqueous solutions of LiCl, NaCl, KCI, CaCl2 and AlCl3. As observed for the hydrolyzed hydrogel (H-carragPAM), it was found that a 'charge screening' action of small cations and carboxylate anions affected the swelling in univalent salt solutions. In the case of the non-hydrolyzed hydrogel (carragPAM), however, a converse trend was observed. As a result, carragPAM and H-carragPAM superabsorbent hydrogels showed a maximum swelling of 45 and 135 g/g in LiCl and KCl solutions, respectively. Due to the high swelling capacity in salt solutions, the hydrogels may be referred to as anti-salt superabsrbents. The swelling of superabsorbing hydrogels was examined in buffer solutions with pH values ranging between 1 and 13. The H-carragPAM hydrogel exhibited a pH-responsie character so that a swelling-deswelling pulsatile behavior was recorded at pH 4 and 9. The swelling kinetics of H-carragPAM were preliminary investigated.
authors.affiliation: Polymer Research Laboratory, Department of Chemistry, Sharif University of Technology, Tehran, Iran.
authors.forename: H
authors.initials: H
authors.lastname: Hosseinzadeh
authors.forename: A
authors.initials: A
authors.lastname: Pourjavavdi
authors.forename: M J
authors.initials: MJ
authors.lastname: Zohuriaan-Mehr
mesh_terms: D000042:Absorption; D002351:Carrageenan / Q000737:chemistry*; D002712:Chlorides / Q000494:pharmacology; D003432:Cross-Linking Reagents; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008670:Metals / Q000494:pharmacology
chemical_list: D002712:Chlorides; D003432:Cross-Linking Reagents; D020100:Hydrogels; D008670:Metals; D002351:Carrageenan