Resumen:
ultilayers of poly(acrylic acid), PAA, and
chitosan, CHI, have been built by the layer-by-layer (LbL)
method from aqueous solutions at different pH values
and analyzed by the dissipative quartz crystal microbalance
(D-QCM) and ellipsometry. The results showed that under all
of the assembly conditions considered the growth of the films is
nonlinear. The thickness of the PAA layers increases as the pH
of the assembling solutions decreases, whereas the adsorption of
CHI is almost unaffected by the pH conditions. The comparison
of the thickness obtained by D-QCM and by ellipsometry has
allowed us to calculate the water content of the films, showing
that the multilayers are highly hydrated, with an average water
content higher than 20%. The analysis of D-QCM data has
provided high-frequency values of the complex shear modulus
that are in the megapascal range and shows a transition from
mainly viscous to mainly elastic behavior for the added PAA
layers, depending on the pH.