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Journal of Thermal Analysis and Calorimetry
Authors: Yuri Park, Godwin A. Ayoko, Janos Kristof, Erzsébet Horváth, and Ray L. Frost

. In this study, Na-montmorillonite is used to prepare organoclays and two types of cationic surfactants namely: dodecyltrimethylammonium bromide (DDTMA) and didodecyldimethylammonium bromide (DDDMA) are chosen as examples of mono- and di-alkyl cationic

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Abstract  

Calorimetric measurements of adsorption for the surfactant (benzyldimethyldodecylammonium bromide) and its polar head-group (benzyltrimethylammonium bromide) from aqueous solutions on two different silica surfaces (hydrophilic and hydrophobic one) allow a more detailed picture of the subsequent stages of the adsorption process to be drawn. It is possible to determine more precisely a boundary between the adsorption of individual molecules and the formation of surface aggregates. The local disruption of the structure of the interfacial water molecules by surfactant cations gives an endothermic contribution to the total enthalpy of displacement. This contribution depends on the length of alkyl chain as well as on the type and the origin of solid surface.

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Abstract  

The Rose Bengal forms with cationic surfactants /1-carbethoxypentadecyltrimethyl-ammonium bromide, cetyltrimethylammonium bromide and cetylpyridinium bromide/ the extractable ion associates with composition 11 or 12. The extraction constants of the ion associates of the Rose Bengal with cationic surfactants were determined radiometrically with the aid of Rose Bengal labelled with131I.

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Three methyl groups containing quaternary ammonium compounds have been separated and identified by thin-layer chromatography using green solvents. Silica gel G and n-butanol-40% aq. ethylene glycol-ethyl acetate (6:4:1) have been found the most favorable for the resolution of three cationic surfactants (cetrimonium chloride-benzyl trimethylammonium chloride-tetramethylammonium hydroxide). Densitographic separation pattern has been presented. The limits of detection for cetrimonium chloride, benzyl trimethylammonium chloride, and tetramethylammonium hydroxide have been determined. The mobility trend of separated surfactants was also examined by replacing n-butanol with other alcohols. Chromatographic parameters like ΔR F, separation factor (α), and resolution (R S) for the separation have been calculated. The effect of the presence of foreign substances such as metal cations, metal anions, amino acids, and vitamins as impurities on separation has been examined. The proposed method has been successfully applied for the identification of cetrimonium chloride in commercially available shampoo sample.

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Abstract  

Heat capacities of aqueous solutions of cetyltrimethylammonium (CTA) salicylate, of CTA m-hydroxybenzoate and of CTA p-hydroxybenzoate were measured using a scanning microcalorimeter. Only the salicylate solution exhibited heat-capacity anomaly around 330 K, depending on the heating rate. The transition enthalpy was 3.5±0.2 kJ mol–1, which was similar to that observed in solution of 1:1 intermolecular compound between CTA bromide (CTAB) and o-iodophenol (OIPh). The enthalpy of formation H f of the 1:1 intermolecular compound from CTAB and OIPh was determined by measuring the enthalpies of solution of the relevant crystals into ethanol. Positive value f H=3.0±0.3 kJ mol–1 was explained from a large difference between the heat capacities of the 1:1 compound and 1:1 mixture of the component crystals.

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Abstract  

The effects of different cationic surfactants (n-undecylammonum chloride, UDACl and dodecyldimethyl (dodecyloxymethyl) ammonium chloride, DDMDDACl) on fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles have been studied. In the studied systems the molar ratio (x) of DPPC/surfactant ranged between x=0.0164–0.82 and from x=0.0352–1.76 for DPPC/DDMDDACl and DPPC/UDACl, respectively. For both systems, the enthalpy associated with the phase transition significantly decreases even at the lowest surfactant concentration. Also the main phase transition temperature is shifted towards lower temperatures. The structural parameters of the phases have been characterised by small angle X-ray scattering (SAXS). The SAXS results have proved that UDACl at x=0.0352 molar ratio significantly influences the DPPC lamellar structure, while its total disappearance was observed for x=0.176. The presence of DDMDDACl causes a total disappearance of the DPPC lamellar structure already at the lowest molar ratio (x=0.0352). Each surfactant in the system with DDPPC leads to a mixed micellar phase formation.

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Journal of Thermal Analysis and Calorimetry
Authors: Yuri Park, Godwin A. Ayoko, Janos Kristof, Erzsébet Horváth, and Ray L. Frost

difficulty has been overcome by introducing cationic surfactant molecules into the interlamellar space, and the properties of clay minerals are enhanced as organoclays. In recent years, organoclays have been used of oil-spill clean-up operations [ 2 – 4

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Abstract  

The phase behaviour of the twin-tailed surfactant dioctadecyldimethylammonium bromide with water was studied by DSC, FT-IR, X-ray and polarizing microscope. The phase diagram of DODAB-water system is very similar to that of DODAC-water. The dihydrate is in equilibrium with isotropic solution below 55°C. Above this temperature there is a lamellar liquid crystalline region, in equilibrium with isotropic liquid and solid crystals of DODAB·2H2O, up to 69°C. From 69 to 86°C, the lamellar mesophase is in equilibrium with ‘waxy’ anhydrous DODAB. From 86 to 116°C and very high DODAB content, there is a very narrow region of existence of inverse hexagonal mesophase, in equilibrium via a narrow biphase region with lamellar mesophase. AtT > 116°C an isotropic liquid appears. There seems to exist two different lamellar mesophases, one of them between 10 and 40 wt.% DODAB and the other between 60 and about 97 wt.% DODAB, with a biphase zone between them.

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Thermal and structural properties of surfactant–picrate compounds

Effect of the alkyl chain number on the same ammonium head group

Journal of Thermal Analysis and Calorimetry
Authors: Tea Mihelj, Zoran Štefanić, and Vlasta Tomašić

the investigation of the interactions of single- and multi-tailed cationic surfactants with oppositely charged picrate molecules should provide more valuable information about the nature of interactions of some anionic fragments with different cationic

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modifying M-smectites (where M is an exchangeable cation) with long-chain cationic surfactants or with quaternary ammonium cations are potential candidates for serving as sorbents of different organic compounds, as thickeners in paints, greases, oil

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