Surfactant Aggregation Number Research Articles

Group VA effects on surfactant aggregation number and dye solubilization efficiency

The effects of changing the charge-bearing atom in the polar head of a surfactant ion on micelle size and dye solubilization efficiency were investigated. Replacement of nitrogen in decyltrimethylammonium bromide by phosphorus or arsenic increases the micellar aggregation number by at least 20% in 0.5 m NaBr solutions. The ability of the surfactants to solubilize the dye Orange-OT is only slightly affected by the substitution of phosphorus for nitrogen, but it is lowered appreciably by the substitution of arsenic.

The effect of hydroxyl functionality in the polar head on surfactant aggregation number and dye solubilization efficiency

The effect of introducing the hydroxyl group into the polar head of a surfactant ion on the micellar aggregation number and dye solubilization efficiency was investigated. Substitution of an ethanol group for an ethyl in the decylethyl-, decyldiethyl-, or decyltriethylammonium ion results in an aggregation number increase. Further substitution is accompanied by either an increase or a decrease in aggregation number, depending upon whether or not an ethyl group remains on the head. For surfactants with polar heads capable of serving as solubilization sites, the ratio of moles of orange-OT solubilized to moles of micellized surfactant usually decreases when ethyl groups are replaced by ethanol groups.

Micelle formation of oil-soluble surfactants in nonaqueous solutions: Effect of molecular structure of surfactants

The micellar weight of dialkylsulfosuccinates, dialkyldimethylammonium halides, and polyoxyethylene 2(1,3-dioctoxypropyl) ether in nonaqueous solutions was measured by the vapor pressure depression method. The apparent aggregation number of anionic surfactants approached saturation values above a fixed range of concentration, whereas that of cationic surfactants generally increased with increase of concentration. However, the nonionic surfactant formed no micelles in various solvents. The aggregation number (λ) of both anionic and cationic surfactants generally decreased with increase in the total carbon number of the alkyl group. The aggregation number of the anionic surfactant having the less bulky hydrocarbon group was larger than that of the anionic surfactant having the more bulky hydrocarbon group. The order of magnitude of λ of surfactants having hydrocarbon groups of equal size was anionics⪢ cationics > nonionics in various solvents. These results were compared with the results reported by other authors.