Silica microparticles surface coating by layer-by-layer or polyelectrolyte complex adsorption

This study follows the surface properties modification of some silica particles, by coating with complementary polyelectrolytes by layer-by-layer deposition or by the adsorption of preformed polyelectrolyte complexes. Two polyanions, alginic acid and poly(2-acrylamido-2-methyl-propanesulfonic acid - co - acrylic acid), and chitosan as polycation are used. The influence of the polyelectrolytes structure and the molar ratio between ionic charges on the polyelectrolyte complexes characteristics is investigated by turbidimetry, dynamic light scattering and electrophoresis. The properties of the formed inorganic/organic materials are evaluated comparing the size distribution and zeta and streaming potential of the samples prepared by layer-by-layer or preformed polyelectrolyte complexes adsorption. The surface morphology is evidenced by atomic force microscopy, and some specific surface parameters are discussed. A special attention is paid to the responsiveness of the new composite materials to environmental pH changes, as a function of preparation conditions.