Electrolyte effect on mixed micelle and interfacial properties of binary mixtures of cationic and nonionic surfactants.
In the present work, the adsorption behavior at the liquid-air interface and micellization characteristics of mixtures of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl) polyoxyethylene (TritonX-100) in aqueous media containing different concentrations of NaBr were investigated by surface tension and potentiometry measurements. From plots of surface tension (gamma) as a function of solution composition and total surfactant concentration, we determined the critical micelle concentration (CMC), minimum surface tension at the CMC (gamma(CMC)), surface excess (Gamma(max)), and mean molecular surface area (A(min)). On the basis of regular solution theory, the compositions of the adsorbed film (Z) and micelles (X(M)) were estimated, and then the interaction parameters in the micelles (beta(M)) and in the adsorbed film phase (beta(sigma)) were calculated. For all mole fraction ratios, the results showed synergistically enhanced ability to form mixed micelles as well as surface tension reduction. Furthermore beta was calculated by considering nonrandom mixing and head group size effects. It was observed that, for both the planar air/aqueous interface and micellar systems, the nonideality decreased as the amount of electrolyte in the aqueous medium was increased. This was attributed to a decrease of the surface charge density caused by increasing the concentration of bromide ions.
Department of Chemistry, Tarbiat Modarres University, P.O. Box 14155-4838, Tehran, Iran. javadians@yahoo.com
Soheila
S
Javadian
Hussein
H
Gharibi
Zahra
Z
Bromand
Beheshteh
B
Sohrabi
D000327:Adsorption; D000388:Air; D001965:Bromides / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry; D008823:Micelles; D017830:Octoxynol / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry*; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D001965:Bromides; D002412:Cations; D002593:Cetrimonium Compounds; D004573:Electrolytes; D008823:Micelles; D017670:Sodium Compounds; D013501:Surface-Active Agents; D014867:Water; D017830:Octoxynol; C027938:sodium bromide; D000077286:Cetrimonium