Attractions in sterically stabilized silica dispersions : III. Second virial coefficient as a function of temperature, as measured by means of turbidity

Abstract

Silica particles coated with octadecyl chains and dispersed in toluene exhibit attractions on lowering the temperature. The attraction is supposed to be the result of interactions between the chain segments and solvent. Since light is strongly scattered in the dispersions turbidity measurements are used to study the interactions. It is shown that turbidity (extrapolated to infinite wavelength) gives the same information as angular light scattering, provided the particles are small. A square well potential with a narrow width and a temperature-dependent depth describes quite well the measured second viral coefficients. In addition the refractive index of the particles as a function of wavelength is also obtained.