J. Agric. Food Chem. 2008, 56, 9015–9021
9015
Use of Dicarboxylic Acids To Improve and Diversify the Material Properties of Porous Chitosan Membranes PO-HUI CHEN,† TING-YUN KUO,† FANG-HSUAN LIU,† YA-HSI HWANG,† MING-HUA HO,‡ DA-MING WANG,† JUIN-YIH LAI,§ AND HSYUE-JEN HSIEH*,† Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan; and Research and Development Center for Membrane Technology, Chung Yuan University, Chung-Li, Taoyuan 32023, Taiwan
Several nontoxic dicarboxylic acid solutions (oxalic acid, succinic acid, malic acid, and adipic acid solutions) instead of an acetic acid solution were used as solvents for chitosan dissolution. The amount of free amino groups of the chitosan in the solution decreased due to the ionic cross-linking of the dicarboxylic acids with chitosan. These solutions were used to fabricate porous chitosan membranes. Replacing acetic acid with these dicarboxylic acids for membrane preparation improved the water uptake (by 35% at most), tensile strength (by 110% at most), and elongation capability (by 50% at most) of the membranes. These dicarboxylic acid solutions not only act as solvents but also improve the material properties of the chitosan membranes due to the ionic cross-linking and hydrogen bond formation. In brief, a nontoxic and straightforward cross-linking method has been developed for chitosan material; this method does not result in a brittle product, thus making it better than the use of toxic cross-linking reagents. KEYWORDS: Chitosan; material property; porous membrane; dicarboxylic acid; oxalic acid; succinic acid; malic acid; adipic acid
INTRODUCTION
Chitosan, derived from chitin through the deacetylation process (Figure 1), is an abundant polysaccharide in nature. The molecular structure of chitosan is linear and is assembled with glucosamine and N-acetylglucosamine through β-(1-4) glycosidic linkages (Figure 1) (1-4), with the number of glucosamine units usually more than 60% (1). Chitosan is normally dissolved in acidic solutions of pH
