Influence of different treatments on characteristics of nanooxide powders alone or with adsorbed polar polymers or proteins

Morphological and structural characteristics of a variety of powder nanocomposites with fumed oxides (silica, silica/alumina, silica/titania) and different linear polar polymers (poly(ethylene oxide), poly(ethylene glycol), poly(vinyl alcohol), poly(vinyl pyrrolidone), polydimethylsiloxane and proteins (ossein, gelatine, BSA)), were analyzed using nitrogen adsorption, infrared (IR) spectroscopy, AFM, and TPD MS methods. A monolayer or lower coverage of oxide nanoparticles by linear polar polymers results in relatively small changes in the specific surface area and adsorption capacity compared with similarly treated fumed oxides alone. The pore size distributions of dried solid residual oxide/polymer samples demonstrate a more ordered pore structure than the initial powders. This structure, as well as the morphology of secondary particles, depends slightly on the content of polymers (Cpol) at coverage less than a monolayer. If polymer–polymer interactions are weaker than polymer–oxide interactions, the perturbation degree Ф (normalized to molecular weight of a polymer segment mseg) of surface silanols at fumed silica A-300 depends very weakly on the type of adsorbed polymers. Among the studied polymers only PVA demonstrates Ф(Cpol/mseg) values smaller than the other systems because of the formation of strong hydrogen bonds between PVA molecules.