LOADING AND RELEASE OF A MODEL CATIONIC DYE ONTO/FROM CHITOSAN/POLY(ACRYLIC ACID) POLYELECTROLYTE MULTILAYERS

Polyelectrolyte multilayers of chitosan (CS) and poly(acrylic acid) (PAA) were constructed onto glass slides by the deposition from aqueous solution containing NaCl as support electrolyte. After construction, the CS/PAA multilayers were post-treated, changing the water pH and the ionic strength in order to generate pores inside the polymer matrix. A thermal treatment was further used to stabilize the film morphology. The morphological modifications of the multilayers surface, before and after the post-treatments, were monitored by atomic force microscopy as a function of the number of double layers deposited. The capacity of the CS/PAA multilayer thin films to sorb/release cationic species was evaluated using Toluidine Blue O as a model dye. The stability of the post-treated multilayer thin films in successive sorption/desorption cycles was explained by the formation of amide bonds between ionic groups of CS and PAA.