Abstract. Hybrid polymeric networks composed of polyacrylamide and chitosan were developed to determine their swelling and ascorbic acid delivery kinetics at various chitosan concentrations. The hybrid acrylamide/chitosan hydrogels were synthesized in aqueous itaconic acid solution (1% w/w). Young's modulus was also evaluated for the hydrogels, and the results were correlated with the swelling properties. Swelling experiments were carried out using three different pH solutions: acidic (pH 4 buffer solution), neutral (distilled water) and basic (pH 10 buffer solution). The results of the swelling study showed that the swelling properties of the network varied with the changes of the pH in the swelling solution, as well as concentration of chitosan. When chitosan concentration increased, the swelling capacity diminished, and therefore Young's modulus increased. The results indicated that the swelling process followed a second order kinetics. The ascorbic acid diffusion inside the hydrogel follows a Fickian mechanism. The ascorbic acid diffusion coefficients are reported as a function of chitosan concentration.

The polymerization of vinyl acetate in one-phase o/w microemulsions stabilized with Aerosol OT (AOT) is examined as a function of concentration and type of initiator (V-50 and KPS) and temperature. Conversions and reaction rates increase with increasing concentration of V-50 and temperature. Faster polymerization rates and higher conversions are achieved with KPS because of the different electrostatic interactions between the charged microemulsion droplets and the free radicals of KPS and V-50. Average molar masses and polydispersity indexes (M̄ w/M̄ n) are much smaller than those observed in emulsion polymerization using the same surfactant, even at high conversions. Analysis of the molar mass distribution indicates that chain-transfer reactions to monomer are the controlling chain-growth mechanism in the polymerization of vinyl acetate in AOT microemulsions at all conversions.

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