A 1D- and 2D-NMR Study of an Anionic Surfactant/Neutral Polymer Complex

NMR chemical shifts and linewidth measurements were examined for mixtures of sodium 10-phenyldecanoate (Na ω-PhDec) in deuterated aqueous solutions in the presence of varying compositions of poly(ethylene oxide) (PEO) polymers of 2000 and 4000 molecular weight. In addition, variable temperature NMR spectra and NMR spin lattice relaxation times (T ₁) were obtained for the PEO-4000/Na ω-PhDec system as a function of varying polymer concentrations. As expected, the polymer/surfactant systems exhibit the behaviour typical of that of an anionic surfactant/neutral polymer system with well defined critical aggregation concentrations (CMC) corresponding to the formation of polymer/surfactant complexes below the CMC of the free surfactant. The ¹H-NMR linewidths acquired for the Na ω-PhDec/PEO-4000 system before and after the CMC region of the surfactant indicate that the maximum in the linewidth of the PEO proton peak is reached at approximately twice the CMC of the free surfactant. 2D-NMR NOESY measurements on this system exhibit cross peaks between the PEO protons and the protons on the surfactant backbone, consistent with the location of the phenyl group in the micellar interior. All these NMR experiments are interpreted in terms of the structure of the polymer/surfactant complexes as a function of the system composition.

Review on Anionic/Cationic Surfactant Mixtures

It is commonly known that cationic and anionic surfactants cannot be mixed without the risk of precipitation or instability. However, many studies have shown that not only is it possible to combine cationic and anionic surfactants, but also that this combination can present synergic properties. Mixtures of anionic and cationic surfactants have many unique properties that can be very useful when used properly. The aim of this report is to present relevant information concerning the interaction between anionic and cationic surfactants. A bibliographic review on anionic/cationic mixtures is presented here in order to better understand their properties and possible synergic effects, as this is of practical importance for the chemical industry.

Interaction Between an Anionic and an Amphoteric Surfactant. Part II: Precipitation

Use of amphoteric and anionic surfactants is very common in practical formulations such as shampoos and hand dishwashing products. Precipitation of mixtures of dimethyldodecylamine oxide (DDAO) as an amphoteric surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant were studied at different pH levels. The DDAO is a pH-sensitive surfactant and its protonation can be expressed in terms of a pK _a similar to an acid dissociation constant. The protonated form of DDAO carries a positive charge and precipitates with the oppositely charged SDS. Therefore, precipitation phase boundaries are pH dependent due to the varying degree of DDAO protonation. By combining the use of regular solution theory and the pseudophase separation model to describe micellar mixing nonidealities with the precipitate solubility product constant and the protonation dissociation constant, a model to predict the precipitation phase boundary is presented here. The model agrees well with experimental phase boundaries at different pH levels.

Removal of Direct Yellow 27 Dye by Ionic Flocculation: The Use of an Environmentally Friendly Surfactant

The presence of dyes is one of the main contributors to the organic load in textile effluents. In this study a mixture of surfactants, produced from animal/vegetable fats, was used to remove the Direct Yellow 27 dye from a synthetic wastewater through an ionic flocculation process. It was evaluated the effect of contact time, temperature, and surfactant concentration on dye removal efficiency. It was also evaluated the kinetics, equilibrium, and diffusion mechanism of the process. The kinetics of the process was well described by both Pseudo-second order and Elovich models. The transport of dye molecules to the surfactant flocs is controlled by the external layer. Equilibrium data showed a good fit to the Langmuir model. A removal rate of 93% was achieved in a single stage, after 5 h of contact time.     

Dissolution of Soap Scum by Surfactant Part I: Effects of Chelant and Type of Soap Scum

The equilibrium solubilities of two model soap scums [calcium stearate and magnesium stearate: Ca(C₁₈)₂ and Mg(C₁₈)₂] were measured in aqueous solutions containing three different types of surfactants: methyl ester sulfonate (MES) as an anionic; alcohol ethoxylate (EO9) as a nonionic; and dimethyldodecylamine oxide (DDAO) as an amphoteric with and without a chelating agent [disodium ethylenediaminetetraacetate (Na₂EDTA)]. The solubility of calcium soap scum was generally higher than that of magnesium soap scum, the exception being some DDAO systems. The use of the DDAO surfactant with the Na₂EDTA chelating agent at high pH gives the highest solubilities of both studied soap scums. The soap scum solubility is on the order of 2,000 times that in water at high pH. The DDAO is the most effective surfactant under all conditions. The MES is more effective than the EO9 at low pH with the opposite trend observed at high pH. The synergism from added chelant is generally greater at higher pH and is greatest for DDAO followed by EO9.