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Based on the adsorption of Triton X-100 on silica/water and silica/cyclohexane in-terfaces and the adsorption of Triton X-305 on silica/water interface,two adsorption models havebeen proposed.On silica/cyclohexane interface,the adsorption of Triton X-100 is monomolecularlayer.The molecules in the monolayer are presumed to be attached to the silica surface by theirEO chain such that their hydrocarbon chain are exposed to the cyclohexane phase.On silica/waterinterface,the adsorption of Triton X-100 or Triton X-305 is bimolecular layer.The surfactant mole-cules orientated in the first layer are similar with that on the silica/cyclohexane interface.The moleculesin the second layer are postulated to adsorb on those of the first in the opposite orientation,with EOchain directed toward the adsorption medium.The contact angle of quartz-water-cyclohexane(θ_w)as a function of the concentration ofTriton X-100 and Triton X-305 in water has been measured with quartz plate employing the captivedrop(cyclohexane)technique.The observed θ_w(measured through water)rose from<10°to a maxi-mum of about 120° for Triton X-100 and of about 40° for Triton X-305 as the concentration of sur-factant in water increased,and then fell,as the concentration increased further.The results areconsistent with the proposed adsorption models.
Based on the adsorption of Triton X-100 on silica / water and silica / cyclohexane in-terfaces and the adsorption of Triton X-305 on silica / water interface, two adsorption models havebeen proposed.On silica / cyclohexane interface, the adsorption of Triton X-100 is monomolecular layer. The molecules in the monolayer are presumed to be attached to the silica surface by theirEO chain such that their hydrocarbon chain are exposed to the cyclohexane phase. On silica / waterinterface, the adsorption of Triton X-100 or Triton X -305 is bimolecular layer. The surfactant mole-cules orientated in the first layer are similar to that on the silica / cyclohexane interface. The molecules in the second layer are postulated to adsorb on those of the first in the opposite orientation, with EOchain directed toward the adsorption medium. contact angle of quartz-water-cyclohexane (θ_w) as a function of the concentration of Triton X-100 and Triton X-305 in water has been measured with quartz plate employing the captive drop (cyclohexane) technique.The observed θ_w (measured through water) rose from <10 ° to a maxi-mum of about 120 ° for Triton X-100 and about 40 ° for Triton X-305 as the concentration of sur-factant in water increased, and then fell, as the concentration increased further. The results areconsistent with the proposed adsorption models.