Effect of chain length in ethoxylated and sulfonate surfactants upon the limiting diffusion coefficients in water at 25.0 °C

Abstract

Limiting diffusion coefficients of ethoxylated surfactants of general formula CH₃(CH₂)_p−1(OCH₂CH₂)_qOH (C_pE_q) and sulfonate surfactants of formula CH₃(CH₂)_p−1SO₃ ⁻ Na⁺(C_pSO₃Na) were measured at 25°C by the Taylor dispersion technique. The series C₆E_q, with 0q5, was studied to evaluate the effect of the length of ethoxylic chain, (–OCH₂CH₂–)_q, on the mobility of the surfactant, the series C_pE₅ with 0p8 was studied to evaluate the effect of the length of the hydrophobic group, (–CH₂–)_p. The series C_pSO₃Na was also studied to compare the experimental results with the intradiffusion coefficients obtained by the NMR-PGSE technique and with the data computed by the Nernst–Hartley equation.