Mixed monolayer and mixed micelle formation in binary mixture of surfactants-systems for trioxyethylenated dodecyl sulfonate and some polyoxyethylenated fatty alcohol ether nonionic surfactants

摘要

The interaction and synergism of some polyoxyethylenated fatty alcohol ether (POE) nonionic surfactants (C_(12)E_2, C_(12)E_3, C_(10_E_5, C_(10)E_7, where C_x indicates number of carbon atoms in the chain and E_y indicates number of oxyethylene glycol ethers) with trioxyethylenated dodecyl sulfonate (C_(12)E_3S) in mixed monolayer formation at the surface and in mixed micelle formation in aqueous solutions were studied at 25 and 40 deg C by calculating interaction parameters (beta~(sigma), beta~M) from surface tension-concentration data by use of Rosen's equation based on the nonideal solution theory. All the systems investigated adapt reasonble well to the nonideal model, with negative values of beta~(sigma) and beta~M (where M means micelle and sigma refers to the air-liquid interface) indicating a favorable interaction between the mixed surfactnts. Either at a monolayer or in a mixed micelle, the attractive interaction becomes stronger when the alkyl chain in the POE surfactant is longer, i.e., when the POE becomes more hydrophobic. The interaction increases in the order C_(10)E_7 < C_(10) E_5 < C_(12)E_3, C_(12)E_2. For the two C_(10)E_n (n = 5,7)/C_(12)E_3 systems, as temperature increase from 25 to 40 deg C, the interaction increases in a mixed micelle, but it decreases in a mixed monolayer. Synergism in mixed micelle formation exists for C_(12)E_3S/C_(10)E_n mixtures when X_1~M, the mole fraction of POE in a mixed micelle, is approx0.4-0.8. whereas synergism does not occur in the systems of C_(12)E_3S/C_(12)E_m due to the large difference between CMC_1 and CMC_2, i.e., large |In(C_1~M/C_2~M)| value (where CMC = critical micelle concentration). The degree of synergism in mixed micelle formation is temperature independent and is 0.23, 0.18, and close to zero for C_(10)E_5/C_(12)E_3S, C_(10)E_7/C_(12)E_3S, and C_(12)E_m (m = 2,3)/C_(12)E_3S systems, respectively. Synergism in surface tension reduction effectiveness occurs in C_(12)E_3S/C_(12)E_2 and C_(12)E_3S/C_(12)E_3 systems. The mole fractions of POE in the solution phase are 0.302 and 0.333 for the two mixtures at the point of maximum synergism.