Adsorption of poly(o-methoxyaniline) in layer-by-layer films

The processes governing adsorption of poly(o-methoxyaniline) (POMA) are analyzed by investigating the kinetics of adsorption and adsorption isotherms of a POMA layer on already adsorbed layer-by-layer films of POMA/poly(ethenesulfonic acid) (PVS). The kinetics of adsorption comprises two steps, namely, a first-order fast process followed by a slower process fitted with a Johnson-Mehl-Avrami function, characteristic of nucleation and growth mechanisms. The dependence of the adsorbed amount on the number of interruptions in the adsorption process and on the pH of the POMA solution shows unequivocally that spontaneous adsorption is not caused only by electrostatic attraction, as implied in the traditional layer-by-layer method. For POMA, we present evidence that H-bonding plays a major role either by participating in adsorption through interactions between POMA and PVS molecules or by being responsible for considerable POMA aggregation at high pHs.