含エステル基界面活性剤の研究

ミセル形成に及ぼす電解質の影響

抄録

The effect of additional salt on the critical micelle concentration (cmc) of the sodium sulfoalkyl alkanoates was examined by the change of absorption spectra of pinacyanol chloride. The cmc of the surfactant decreased with increase of addition of sodium chloride, and the logarithm of the cmc was a linear function of the logarithm of total concentration of counter ion. These results were expressed as follows : 1) logcmc=0.55logC-2.47 for C₉H₁₉COO (CH₂) ₂SO₃Na 2) logcmc=0.59logC-2.75 for C₉H₁₉COO (CH₂) ₃SO₃Na 3) logcmc=0.63logC-3.06 for C₉H₁₉COO (CH₂) ₄SO₃Na 4) logcmc=0.59logC-3.24 for C₁₀H₂₁COO (CH₂) ₃SO₃Na 5) logcmc=0.56logC-3.44 for C₁₁H₂₃COO (CH₂) ₂SO₃Na 6) logcmc=0.60logC-3.78 for C₁₁H₂₃COO (CH₂) ₃SO₃Na 7) logcmc=0.64logC-4.05 for C₁₁H₂₃COO (CH₂) ₄SO₃Na The slope of these equations increased with the change of position of the ester group from position near the terminal sulfonate to more central positions of surfactant molecule. These phenomena indicate that the change of cmc with addition of salt was influenced by the position of the ester group in the surfactant molecule.
The dependency of cmc lowering by salt addition to the position of ester group in surfactant molecule will be attributed to the change in counterion binding on micelle surface and also to the change in hydrophobic bond with the position of ester group.