Effect of ph and sodium phosphate dibasic concentration on the swelling properties of chitosan hydrogels [Efecto del ph y la concentracion del fosfato dibasico de sodio en las propiedades de hinchamiento de hidrogeles de quitosana]

In this work were prepared chitosan hydrogels by ionotropic gelation technique with sodium phosphate dibasic (SPD) in an aqueous acetic acid solution 2% v/v. The results obtained shows that the ionic interaction of the NH+ 3 groups liked to the chitosan chain with the SPD anionic groups is depending of the pH of the swelling solvent. Were studied the swelling properties of the chitosan/SPD in function the the swelling media pH (3, 5, 7, and 11) and the percentage of solids in the hydrogel (2, 3, and 4% w/w). In the acid swelling medium the swelling capacity of the hydrogels was higher respect to the capacities obtained in basic and neutral media; moreover with a percentage of solids of 2% w/w the swelling capacities were higher. An overshooting effect in the hydrogels was observed, followed by a lost in the volume of the hydrogels until the swelling equilibrium is attained