Contact angles of selective wetting of hexylamine-modified silica surface

It is shown experimentally that modification of silica particles by short-chain surfactant like hexylamine leads to inversion of selective wetting angle θ of the particles and to phase inversion in the emulsions stabilized by the hexylamine-modified silica particles. Empiric diagram of emulsion stability shows that at the contact angle θ close to 90° there is region of completely unstable emulsions between regions of stable emulsions of oil-in-water and water-in-oil types in the case of volume fraction of oil Øoil = 0.25 or 0.75. At Øoil = 0.5 the emulsion type and stability corresponded to the aqueous phase receding and advancing contact angles.