Kinetics of adsorption of poly(o-methoxyaniline) self-assembled films

The kinetics of adsorption of poly(o-methoxyaniline) (POMA) via self-assembly has been investigated using UV-vis spectroscopy. Though experimental conditions, including type of substrate, affect the amount of polymer adsorbed, adsorption of the first POMA layer on glass substrates was shown to occur in two stages, reaching saturation within a few minutes. The first stage is represented by a first-order kinetics with characteristic times of 5-10 s. The second stage also has an exponential behavior with t(1.5) and characteristic times of hundreds of seconds, which was valid for all substrates when the shift in the polaronic band in the beginning of adsorption was taken into account. The t(1.5) within the exponential is believed to indicate a diffusion-controlled growth of small domains formed during the first stage of adsorption. The appearance of small domains and their subsequent growth are consistent with scanning electron micrographs obtained at distinct time periods of adsorption. When a POMA layer was made to adsorb on an already formed POMA/poly(ethenesulfonic acid) self-assembly multilayer, the adsorption process became faster as the number of bilayers already deposited increased.