Solution Properties of Nonionic Surfactants and Their Mixtures:  Polyoxyethylene (10) Alkyl Ether [C_nE₁₀] and MEGA-10

Abstract

The interfacial and thermodynamic properties of nonionic surfactants and their mixtures are of both theoretical and practical interest. The nonionic surfactants used in this study are polyoxyethylene (10) alkyl ether [CnE10; m ) 10 and n ) 12, 16] and N-decanoyl-N-methylglucamine (MEGA-10). The critical micelle concentrations of pure surfactants and their mixtures were determined by surface tension measurements at different mixed ratios and temperatures. Interfacial parameters such as the maximum surface excess (Γmax) and the minimum area per molecule (Amin) at the air/water interface were also determined from surface tension data. Standard thermodynamic parameters of micellization and adsorption were also computed and discussed. Steady-state fluorescence studies were also carried out to determine the micellar aggregation number (Nagg) and the microenvironment/polarity in the mixed micelle from the I1/I3 ratio. The interaction parameters that measure the interaction between the surfactant molecules in the mixed micelle were computed by Rubingh's approach. 1 H NMR was also used to investigate the interaction between the surfactants.

A Review of Recent Studies on Aqueous Binary Mixed Surfactant Systems

“…Different from the present results, azeotropic points (Azp) were very clearly found for SDS/MEGA-n's mixed systems (at X 2 = 0.25 for SDS/MEGA-8 mixed system, at X 2 = 0.33 for SDS/MEGA-9 mixed system and at X 2 = 0.50 for SDS/MEGA-10 mixed system) 38) . In addition, such an azeotropic phenomenon as seen here has been observed even for mixtures of MEGA-8, -9 and -10 with perfluorooctanoate (SPFO) 15,17,42,43) , although a kind of mutual phobicity acts between hydrocarbon and fluorocarbon chains 42,49) , indicating that the interaction between head groups plays a great role for mixed micelle formation 54,55) .…”

“…1 H NMR was also used to investigate the interaction between the surfactants. The CMC-X 2 relations were found to be of negative deviation from ideal mixing 54) . This is indicative of some interaction between the surfactant molecules, which can possibly be due to (i) the interaction between the head groups of these surfactants through hydration, (ii) a small repulsive interaction between the oxonium ion of polyoxyethylene and the slightly positive nitrogen atom of glucamine, (iii) incorporation of MEGA-10 molecules lowering the steric repulsions between the large oxyethylene head groups, and (iv) reduction in hydration of the hydrophilic moiety of MEGA-10 due to the addition of C 12 E 10 /Brij56.…”

“…was lowered in the presence of NaCl for pure C 12 E 10 and Brij56, MEGA-10 could cause a rise of C.P. for both C 12 E 10 /MEGA-10 and Brij56/MEGA-10 systems 54) .…”

“…The nonionic surfactants introduced here are polyoxyethylene (10) alkyl ether [C n E m ; m=10 and n=12, 16] and MEGA-10. The CMC's of pure surfactants and their mixtures were determined by surface tension measurements at different mixed ratios and temperatures 54) . Interfacial parameters such as the maximum surface excess (G max ) and the minimum area per molecule (A min ) at the air/water interface were also determined from surface tension data.…”

“…However, the addition of NaCl depresses the C.P. of polyoxyethylene alkyl ethers 54) . This indicates that there is a considerable difference between the hydration of hydroxyl group of MEGA-10 with water and that of the oxyethylene groups of polyoxyethylene alkyl ether with water.…”