Band 51, Heft 1

In this paper different amine alginate salts were prepared by neutralization of alginic acid with amine compounds (triethanol amine, tri-isopropanol amine and hexamine). The chemical structures of the prepared compounds were confirmed using Gel Permeation Chromatography (GPC) and Fourier Transform Infrared Spectroscopy (FTIR). The surface properties of the target surfactants were studied and the surface parameters were determined; including surface tension, critical micelle concentration, maximum surface excess and minimum surface area, with and without addition of dodecytrimethyl ammonium bromide as a co-surfactant. Finally, the standard free energies of micellization and adsorption of the prepared surfactants were calculated. The obtained results indicated that, the adsorption activity of the three prepared alginate salts had increased by addition of very low concentration (0.0005 m/L) of DTAB surfactant, owing to the formation of an electrostatically stabilized Surfactant-Polyelectrolyte Complex.

We present a quantitative method to determine the phase transition temperatures between one-phase and two-phase regions of multi-component liquid mixtures via temperature-dependent transmission measurements with an UV/Vis spectrometer. The method is based on the fact that multi-phase samples are turbid, while one-phase samples are transparent. We describe the method in detail and discuss the choice of the experimental parameters (wavelength, sample layer thickness), a suitable temperature program as well as the data analysis. We prove the validity of our method by measuring the phase diagrams of two model systems, namely a liquid and a gelled microemulsion. The results are in good agreement with those obtained with the conventional visual method used for phase studies.

Dimeric Gemini sulfonate surfactants 1,2-di-(2-oxoypropyl sulfonate-3-alkylether- propoxy) ethane were prepared by the reaction of ethylene glycol diglycidyl ether with long-chain alcohols, followed by sulfonation with 1,3-propane sultone. Ethylene glycol ether was synthesized by the reaction of epichlorohydrin with ethylene glycol. The chemical structures of the prepared compounds were confirmed by FTIR, 1 H NMR and elementary analysis. With the increasing length of the carbon chain, the values of their CMC initially decreased. The longer alkyl chain is, the higher melting point is. The Krafft point of Gemini sulfonate surfactants was below 0°C and they had good water solubility. These compounds were superior in surface active properties to general sulfonate surfactants SDS. The efficiency of adsorption at the water/air interface (pC 20 ) of these surfactants was very high. Their foaming properties and wetting ability toward a felt chip, and lime-soap dispersing ability were investigated.

The high amount of surfactant needed to formulate a bicontinuous microemulsion is a limiting factor for industrial usage of these systems. Commercially available triblock copolymers can be obtained in high amounts. Here, we show the influence of size and composition of different poly(ethyleneoxide)-poly(propyleneoxide)-poly(ethyleneoxide) triblock copolymer surfactants (Pluronics) on a technical grade sugar surfactant microemulsion. The so-called efficiency boosting can also be realized in such technical grade systems. The resulting efficiency boosting is studied systematically with regard to the impact of the polymer size and the composition of the system.

The inhibition of calcium carbonate (CaCO 3 ) precipitation by “green” additives has been examined in aqueous solution. It has been found that additive performance as CaCO 3 inhibitor depends upon additive architecture. The influence of surfactants containing different functional group has also been investigated. Results on the evaluation of surfactants suggest that compared to carboxyl group containing additives, surfactants are ineffective CaCO 3 inhibitors. Performance data on the impact of cationic surfactant (e. g., cetyltrimethyl ammonium chloride, CTAC) suggest that CTAC exhibits an antagonistic effect on the performance of polymers. The antagonistic behavior shown by CTAC on the performance of additives has been explained in terms of cationic – anionic interactions. SEM study shows that presence of low concentration of additive exhibits marked influence on the morphology of CaCO 3 crystals formed in presence of additives.

This paper aims to provide analysis of the influences of concentration changes of the surfactant – benzyldimethylhexadecylammonium chloride in hydrogels on their liberation, rheological, association and solubility properties. The hydrogels contained constant amounts of the gel-creating basis (polymer chitosan – 2.5 % w/w), the drug (chlorhexidine dihydrochloride – 0.1 % w/w) and the surfactant, which was used as an enhancer (0.005 – 0.05 % w/w). The highest value of the released drug corresponded to the highest surfactant concentration in the hydrogel. Critical micelle concentration and thermodynamic parameters, molar Gibbs energy, enthalpy and entropy of micellization were calculated. A linear increase of the surfactant amounts in hydrogels caused a non-linear increase of the cloud point. The appearance of the surfactant's associates in hydrogels influenced both their liberation and rheological properties.

Two cationic quaternary ammonium surfactants with hydroxyethyl groups, dodecyl-(2-hydroxyethyl)-dimethylammonium chloride (DHDAC), and dodecyl-di(2-hydroxyethyl)-methylammonium chloride (DHHAC) were synthesized. Their physicochemical properties were investigated systematically by surface tension and conductivity measurements. Various physicochemical parameters were calculated to evaluate the surface activities of these surfactants. The results show that the surface activity increases with increasing the number of hydroxyethyl groups on hydrophilic groups of surfactants. The degrees of counterion binding to micelles of these surfactants were also discussed. The thermodynamic parameters obtained from electric conductivity measurements show that the micelle formation of DHHAC is entropy-driven in the temperature range investigated. However, it is enthalpy-driven for DHDAC.

Indigenous kaolin was collected from Swat district and then activated. The samples were characterized by BET surface area, FTIR, XRD, SEM, EDS, TGA/DTA, zeta potential and particle size analysis. Adsorption of basic red 5 on each sample was studied by adsorption kinetics at 20 °C, 30 °C and 40 °C. The residual concentration of the dye was determined by using UV–Vis spectrophotometer. The removal of basic red 5 from water solution was studied with respect to dye concentrations and equilibration time. Adsorption kinetics on kaolinite surface were analyzed by using parabolic diffusion, Elovich and Bangham models. Thermodynamic parameters like ΔE # , ΔH # and ΔS # were calculated from the adsorption kinetics data. The results show that the adsorption is a spontaneous and endothermic process. The negative value of entropy shows that the dye molecules take a proper position on the surface.