Thin multilayer films of weak polyelectrolytes on colloid particles

We report the the formation poly(acrylic acid) (sodium salt) (PAA) and poly(allylamine hydrochloride) (PAH) multilayers en polystyrene (PS) and melamine formaldehyde (M-F) colloid particles by the layer-by-layer (LbL) assembly technique. The use of different solution processing conditions (e.g., H and ionic strength) was found fro have a pronounced effect on film growth, with the degree of dissociation of both polyelectrolytes (PEs) playing an important role for regular PAA/PAH multilayer growth. To retain colloidal stability during to sequential adsorption of PEs, if vas essential to deposit the PE layers from adsorption solutions where the PEs are in a highly charged state, the degree of which was regulated by varying the pH. Thicker PAA/PAH coatings were obtained when the pH value of the PAA deposition solution was close the ply. value of PAA in solution. The presence of salt in the deposition and rinsing solutions also promoted the formation of thicker PAA/PAH coatings. The zeta-potential of the particles, measured at different pH values, allowed estimation of the isoelectric plaint (pI) of the adsorbed layers. The pI values of the coatings showed a dependence en the nature of the underlying layers and particle surface, particularly when PAA formed the outermost layer. A pI of eras observed for PAA adsorbed on bare IF panicles, compared with a pI of 2.5 for (PAA/PAH)(2)-coated PS spheres. The formation of hallow PAA/PAH capsules, achieved by removal of the core from the PAA/PAH-coated colloids, further confirmed the deposition of PAA and PAH multilayers. The techniques of microelectrophoresis, fluorescence spectroscopy, and transmission electron microscopy were used to characterize the layer buildup and film morphology. The formation of PAA/PAH multilayers en colloids highlights the potential of weak PEs for exploitation in colloid surface modification and encapsulation technologies.