Authors Kato, N; Schuetz, P; Fery, A; Caruso, F.
Title Thin multilayer films of weak polyelectrolytes on colloid particles
Date 21.11.2002
Number 3104
Abstract We report the formation of poly(acrylic acid) (sodium salt) (PAA) and poly(allylamine hydrochloride) (PAH) multilayers on polystyrene (PS) and melamine formaldehyde (MF) colloid particles by the layer-by-layer (LbL) assembly technique. The use of different solution processing conditions (e.g., pH and ionic strength) was found to 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 the sequential adsorption of PEs, it was 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 to the pKa 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 ·-potential of the particles, measured at different pH values, allowed estimation of the isoelectric point (pI) of the adsorbed layers. The pI values of the coatings showed a dependence on the nature of the underlying layers and particle surface, particularly when PAA formed the outermost layer. A pI of 5.5 was observed for PAA adsorbed on bare MF particles, compared with a pI of 2.5 for (PAA/PAH)2-coated PS spheres. The formation of hollow 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 on colloids highlights the potential of weak PEs for exploitation in colloid surface modification and encapsulation technologies.
Publisher Macromolecules
Wikidata 117
Citation Macromolecules 35 (2002) 9780-9787
Tags light-emitting-diodes self-assembly technique by-layer adsorption molecular films glucose-oxidase charged surfaces adsorbed layers energy-transfer nanoparticles electroluminescence

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