Effect of the Molecular Structure on the Adsorption Properties of Cationic Surfactants at the Air–Water Interface

Abstract

The surface activity and thermodynamic properties of adsorption at the air–water interface of two series of cationic surfactants based on isourea: the O‐dodecyl‐N,N′‐diisopropylisourea hydrochloride, hydrobromide, and hydroiodide and the O‐tridecafluorooctyl‐N,N′‐diisopropylisourea hydrochloride and hydrobromide were studied. The effect of structural parameters as the nature of the halide counter ion and the nature of the non‐polar chain on the surface activity and thermodynamic properties of adsorption were investigated. The surface parameters, the maximum surface excess concentration (Γmax), the minimum area per molecule (Amin) at the aqueous solution‐air interface, effectiveness of surface tension reduction (πCMC), and efficiency of surface tension reduction (pC20) were estimated. The standard Gibbs free energy of adsorption, (ΔG°ads) change has been calculated at different temperatures.

Influence of Poloxamer 407 on Surface Properties of Aqueous Solutions of Polysorbate Surfactants

“…The maximum surface excess (Γ max ) value is regarded as a measure of the adsorption effectiveness (Szymczyk and Jańczuk, ). The Γ max value can be obtained by surface tension measurements, based on the Gibbs adsorption isotherm (Azum et al, ; Bagheri and Khalili, ; Kamil and Siddiqui, ; Karpichev et al, ; Lehanine and Badache, ): where m is a constant, which specifies the number of species, formed by a surfactant dissociation in a water solution, whose concentration at the interface changes with change of the surfactant concentration in the bulk phase. In the case of binary surfactant mixtures m = m 1 x 1 + m 2 x 2, where m 1 and m 2 are the number of species formed by dissociation of surfactant 1 and 2, respectively, while x 1 and x 2 represent the mole fractions of surfactant 1 and 2, respectively, in the mixed monolayer having surfactants 1 and 2.…”

“…Minimum surface area per molecule can be calculated according to following equation, if the maximum surface excess value for a surfactant or surfactant mixture is known (Azum et al, ; Bagheri and Khalili, ; Kamil and Siddiqui, ; Karpichev et al, ; Lehanine and Badache, ): where N A is Avogadro constant.…”

“…It is also commonly known that properties of individual surfactants can be improved by mixing with other amphiphiles (Azum et al, ; Bagheri and Khalili, ; Ćirin et al, ; Ćirin and Poša, ; Holland and Rubingh, ; Hua and Rosen, ; Kamil and Siddiqui, ; Karpichev et al, ; Lehanine and Badache, ; Rosen and Hua, ; Rosen and Zhu, ; Schillén et al, ). One of the main reasons for this phenomenon is the existence of synergism, i.e., nonideal behavior, in surfactant mixtures.…”

Synthesis and application of non-bioaccumulable fluorinated surfactants: a review

“…Generally, the hydrocarbon moieties are introduced into these surfactant molecules to further increase the hydrophobicity and improve the surface activity. Lehanine et al [42] synthesized a perfluorinated hexyl cationic fluorinated surfactants based on isourea, in which the condensation of a diisopropylcarbodiimide and a fluoroalkyl alcohol was used to obtain a fluorinated diisopropylisourea intermediate and then the intermediate reacted with the hydrohalogenated acid (HX, X=Cl or Br) to yield a salt ([((CH3) 2 CHNH) 2 COCH 2 CH 2 (CF 2 ) 5 CF 3 ][X], C8IF-X, X= Cl or Br) with surface activity. Since the perfluorinated hexyl and the hydrocarbon moiety can together improve hydrophobicity of surfactants, the prepared surfactants showed higher surface activity.…”