Activity Coefficients at Infinite Dilution and Critical Micelle Concentrations of Poly(oxy-1,2-ethanedyil), α-Tridecyl-ω-hydroxy Ethers (C_(13)E_(i=6,10,18)) in Aqueous Media by the Volmer Surface Equation of State and Group Contributions

摘要

Activity coefficients at infinite dilution and the critical micelle concentration of three different poly(oxy-1,2-ethanedyil), α-tridecyl-ω-hydroxy ethers (POEs) (6, 10, and 18 mol) were determined from surface tension data in aqueous solution at 20 ℃. Measurements were made with the ring tensiometer. As is the case for other members of the polyethoxylated alcohols family, experimental data obey the Volmer surface equation of state which contains either the critical micelle concentration or the activity coefficient at infinite dilution among its constitutive parameters. As expected, it was found that the critical micelle concentration values increased (cmc x 10~6 = 2.15, 2.87, and 6.08) and the activity coefficients at infinite dilution decreased (γ~∞ x 10~(-5) = 4.7, 3.5, and 1.6) when the ethylene oxide content increased. The individual contributions of the ethoxy, hydroxide, and methylene groups found for other polyethoxylated surfactants were used to calculate the critical micelle concentration; the calculated values agree with the experimental values obtained by the Volmer surface equation of state.