Adsorption and Micelle Formation of Mixed Surfactant Systems in Water. I. A Combination of Top-heavy Type Anionic Surfactants.

Abstract

The micellization and adsorbed film formation for an aqueous binary mixed system of anionic top-heavy type surfactants: sodium salt of a-sulfonatomyristic acid isopropyl ester (a-SMy iPr) and sodium 1-oxo-1 [4-(tridecafluorohexyl) phenyl]-2-hexanesulfonate (FC6-HC4), were studied by means of surface tension measurement (drop volume method). The surface tension (g) was precisely measured for the solutions of the respective single and eleven mixed systems at 30.00 0.03 in order to determine critical micellization concentrations (CMC) and surface excesses (G) as a function of net mole fraction of FC6-HC4 (X FC6-HC4). The effect of added NaCl on CMC was examined for each single system to determine the degree of counterion binding (b i) from the Corrin-Harkins plot. Using the data of CMC and b i , we estimated the micellar composition (Y FC6-HC4), activity coecients (f i) of the two surfactants in mixed micelles, and the interaction parameter (w 0), the calculation of which was made on the basis of our own theoretical equations taking into account of mutual counterion effect in binary ionic surfactant mixtures. From the CMC-Y FC6-HC4 curve, markedly positive and slightly negative deviations from ideal mixing micelle formation were found, i.e. the positive deviation at the range of 0 < X FC6-HC4 < ca. 0.3 and the slightly negative deviation at the range of ca. 0.3 < X FC6-HC4 < 1. On the other hand, the composition of adsorbed film (Z FC6-HC4) was also estimated as a function of X FC6-HC4 using the surface tension data from below CMCs. In addition, G was determined as functions of X FC6-HC4 and Z FC6-HC4 and the partial molecular area (PMA) was evaluated from the plot of mean molecular surface area (A m) vs. Z FC6-HC4. All the data obtained showed without exception that an addition of 10 to 20% a-SMy iPr to FC6-HC4 results in a marked enhancement of surface activity and micelle formation ability, accompanying a favorable packing in two-dimensional or three dimensional structuring by the two top-heavy type surfactants, and that the two or three dimensional structures are thermodynamically more stable due to higher FC6-HC4 content.

A Review of Recent Studies on Aqueous Binary Mixed Surfactant Systems

“…As has been reported previously 35) and showing again in the frame , the CMC/ C 20 -X 2 relation has two breaks corresponding to the other properties already seen in and . In the BAGTB/ HTAB mixed system too, the situation is similar to BAGTB/MEGA-10 mixed system in regard to the discontinuity and parallelism of G min (S) with CMC/C 20 .…”

“…The obtained m t -Z 2 curve as well as the m t -X 2 curve shows a markedly negative deviation and correspondingly, the curve results in a large negative value of w A for all the mixed systems. In addition, the absolute values of the negative w A are greater than those of micelles ( w A w R ); this situation is similar to that of various mixed systems of MEGA-n's 29,[35][36][37][38][39]43) . The increasing order of the absolute values (w A ) is in parallel with the order of hydrophobicity or hydrocarbon chain length: w A = -5.0 for CHAPS/MEGA-8 mixed system, w A = -2.2 for CHAPS/MEGA-9 mixed system and w A = -1.5 for CHAPS/MEGA-10 mixed system (It may be of interest to compare these results with those of SDS/MEGA-n's mixed systems: -4.2 for SDS/MEGA-8 mixed system, -4.4 for SDS/MEGA-9 mixed system and -4.5 for SDS/MEGA-10 mixed system.)…”

“…All the materials used for this series work have been described in terms of their sources and purities in the respective reports [35][36][37][38][39][40] . It may be worth noting the surface tension measurements even in the present review paper.…”

“…Previously, we have reported some studies performed by means of surface tension measurements as a series of works, i.e., adsorption and micelle formation of mixed surfactant systems in water I: a combination of top-heavy type anionic surfactants 35) , II: a combination of cationic Gemini-type surfactant with MEGA-10 36) , III: a comparison between cationic Gemini/cationic and cationic Gemini/ nonionic combinations 37) , and IV: three combinations of one of the most typical anionic surfactant, sodium dodecylsulfate (SDS) with MEGA-8, -9 and -10 (MEGA-n's) 38) , in addition to three combinations of zwitterionic surfactant, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid (CHAPS) which is a derivative of cholic acid in pH 7.2 phosphate buffer solution. These works have followed the previous surface tension study on binary mixed systems of…”

“…and , the determination of m t is indispensable to estimate the values of Z 2 and w A . An example, how to determine m t values is shown in 35) , and in are demonstrated the joint phase diagrams showing m t -X 2 and m t -Z 2 relations for the combinations of a-SMy Pr/FC6-HC4 35) , BAGTB/HTAB and BAGTB/MEGA-10 mixed systems 37) .…”