A Convenient One-Step Preparation of Chitosan- Poly(sodium acrylate-co-acrylamide) Hydrogel Hybrids with Super-Swelling Properties G. R. Mahdavinia, 1 A. Pourjavadi, 1 M. J. Zohuriaan-Mehr 2 1 Department of Chemistry, Polymer Research Laboratory, Sharif University of Technology, Tehran, Iran 2 Superabsorbent Hydrogel Division, Iran Polymer and Petrochemical Institute (IPPI), Tehran, Iran Received 8 May 2005; accepted 8 June 2005 DOI 10.1002/app.22521 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Hydrogel hybrids were conveniently pre- pared from alkaline hydrolysis of chitosan–poly(acryloni- trile) mixture under highly practical conditions. The reaction of chitosan alkoxide anions with nitrile groups of poly(ac- rylonitrile) (PAN) forms crosslinking points and results in a three-dimensional network with superswelling ability in aqueous media. The hydrogel hybrid was identified using FTIR spectroscopy. The PAN content of the hydrolyzing feed affects proportionally the swelling capacity of the hy- drogel hybrid. The swelling properties (capacity and rate) of the ampholytic hydrogel were investigated preliminarily. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1615–1619, 2006 Key words: chitosan; polyacrylate; hydrogel; superabsor- bent; swelling INTRODUCTION There has been considerable interest in recent years in the development of materials with the capacity for absorbing massive amounts of water. These materials are defined as superabsorbent hydrogels. Hydrogels are crosslinked hydrophilic polymer networks, which can absorb and retain aqueous fluids within their structure without dissolution. 1–2 Recently, much attention has been paid to chitosan as a potential polysaccharide resource. Chitosan is a biodegradable copolymer composed of d-glucosamine and N-acetyl-d-glucosamine. 3 Because of their excel- lent biocompatibility and biodegradability, chitosan and its derivatives were widely applied to fabrication of biomedical materials, enzyme and cell immobiliza- tion, especially for controlled drug delivery. 4 In recent decades, considerable interest has been focused on modification by grafting synthetic polymers onto the most abundant naturally occurring polysaccharides such as cellulose, starch, alginate, carrageenane, chi- tosan, and etc. Many works have been reported on the preparation of chitosan hydrogels via grafting of var- ious hydrophilic monomers. Graft polymerization of hydrophilic monomers onto chitosan enhances hydro- philicity and water uptake capacity of the backbone. Acrylonitrile (AN), a hydrophobic monomer, com- prises nitrile group (OCN) on its structure. Graft co- polymerization of AN onto polysaccharides, such as starch 5 and chitosan, 6 have been reported. When ni- trile groups are hydrolyzed, they converted to amide (CONH 2 ) and carboxyl (COOH) groups. Anionic hy- drogels can be obtained by saponification of poly(ac- rylonitrile) (PAN)-grafted starch 7 and chitosan. 8,9 Chi- tosan, a basic polysaccharide, comprises amine (NH 2 ) groups on its backbone. Recently, an ampholytic hy- drogel has been prepared through alkaline hydrolysis of chitosan-g-PAN copolymer. 8 The hydrogel formation was based on early reports of Fanta et al. 10,11 published in 1982, demonstrated that PAN can simultaneously and be saponified crosslinked in aqueous alkali in the presence of starch to produce gel. In fact, crosslinks could be formed between the alkoxide ions of starch and the nitrile groups of PAN. In this work, we attempted to extend the idea in the case of a basic biopolymer. Thus, we saponifed the chitosan–PAN mixture by an aqueous alkali to yield superabsorbing hydrogel hybrids. The swelling behavior of resulted hydrogels was prelimi- narily investigated. EXPERIMENTAL Materials Chitosan sample (DD 0.76) was prepared from chitin (extracted from shrimp shell) in our laboratory. 6 Poly- acrylonitrile (PAN) was synthesized through a method mentioned in the literature. 12 All other mate- rials were used as received. Correspondence to: A. Pourjavadi (purjavad@sharif.edu). Journal of Applied Polymer Science, Vol. 99, 1615–1619 (2006) © 2005 Wiley Periodicals, Inc.