Effect of Laponite and a nonionic polymer on the absorption character of cationic dye solutions.

The effect of Laponite and an amphiphilic triblock copolymer of poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) (PEO(99)-PPO(65)-PEO(99), and labeled F127) on the absorption character of two cationic dyes, methylene blue and toluidine blue O, was studied and interpreted in terms of the changing state of aggregation of the dye molecules. The combined effect of the polymer and Laponite on dye absorption was significantly different from their individual influences. Specifically, the presence of Laponite resulted in an increase in monomer population by dispersing the dye on the silicate surface. The presence of F127 also resulted in an increase in the dye monomer population, although to a smaller extent. The combined effect of the polymer and Laponite was an increase in the dimer or aggregate populations attributed to the competition of F127 with the dye molecules for the silicate surface.

Small-angle neutron scattering from surfactant-assisted aqueous dispersions of carbon nanotubes.

The mechanism of surfactant-assisted dispersion of single-walled carbon nanotubes in water is studied by small-angle neutron scattering. The previously hypothesized formation of cylindrical micelles with the nanotubes forming the core of cylinders is inconsistent with the data presented. The scattering data favor a random structureless adsorption model for the dispersion of the nanotubes.