Surface and volume properties of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide

Abstract

Surface tension measurements were carried out for aqueous solutions of two cationic surfactants: dodecylethyldimethylammonium bromide (C(12)(EDMAB)) and benzyldimethyldodecylammonium bromide (BDDAB). Isotherms and thermodynamic adsorption parameters were determined from the surface tension data. Firstly, the surface excess concentration in the adsorbed monolayer and the total concentration of the surfactants were determined, then the standard free energy of adsorption was calculated by different methods. In the calculations, different orientations of the surfactants at the adsorbed monolayer were also taken into account. From the experimental and calculated data it results that the difference in the structure of the two cationic surfactants by changing the methyl group for aryl one in their heads causes an increase of the efficiency and a decrease of the effectiveness of adsorption at water-air interface, and that the standard free energy of adsorption can be predicted from the surface tension of the surfactants assuming the aryl group to be equivalent to 3.5 methylene groups. The experimentally obtained difference between the standard free energy of adsorption of the C(12)(EDMAB) and BDDAB was in good agreement with that theoretically accounted, corresponding to the standard free energy of adsorption of the aryl group. However, the best correlation between the values was obtained when a parallel orientation of the surfactant molecules at the adsorbed monolayer was taken into account.

Surface and volume properties of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide

“…From our previous paper [1] it appears that there are sharp break points on the γ LV -log C curves, which correspond to the critical micelle concentration (CMC) of the surfactant. In the case of the density vs log C curves ( that both for C 12 (EDMAB) and BDDAB a higher value of CMC was obtained from density measurements.…”

“…The C 20 value is the surfactant molar concentration required to reduce the surface tension of the solvent by 20 mN/m and pC 20 is the negative logarithm of this value [1]. The C 20 values for C 12 The CMC/C 20 value is larger for BDDAB (12) than for C 12 (EDMAB) (2.5).…”

“…The CMC values of C 12 (EDMAB) and BDDAB determined on the basis ofFig. 1from our previous paper[1] and Figs. 2 and 3 (curve 1 and curve 2) are: 9.9 × 10 −The relationship between the values of the density (ρ) of aqueous solutions of C 12 (EDMAB) (curve 1) and BDDAB (curve 2) and the concentration of the surfactants (log C ).…”

Analysis of Adsorbed Layers of Benzyldimethyldodecylammonium Bromide on Silica Particles in Water Using the Sorbent Mass Variation Method

“…Amorphous SiO 2 is a widely used adsorbent, ,,,− ,− , and the adsorbed layer structure of the nonionic surfactant alkyl polyoxyethylene ether (C n EO m ) was investigated using SANS − and ellipsometry . Benzyldimethyldodecylammonium halide (BDDA + X – , commonly X – = Cl – and Br – ) is one kind of quaternary ammonium surfactants and widely applied in clinical, cosmetic, and industrial areas. − However, research studies on the aggregation features of BDDA + X – at solid–liquid interfaces ,, as well as in solutions ,, are scarce. Harkot and Jańczuk studied the effect of BDDABr adsorption on the wetting of polytetrafluoroethylene and poly­(methyl methacrylate) surfaces.…”