A conductometric study of interactions between gelatin and sodium dodecyl sulfate (SDS) in aqueous-rich mixtures of dimethylsulfoxide

Interaction of sulphone based reactive dyes with cationic surfactant: a spectroscopic and conductometric study

Interaction of sulphone based reactive dyes, designated as dye-1 and dye-2, with cationic micellar system of cetyltrimethylammonium bromide (CTAB), has been investigated by spectroscopic and conductometeric measurements. Efficiency of the selected micellar systems is assessed by the values of binding constant (K b ), partition coefficient (K x ) and respective Gibbs energies. Critical micelle concentration (CMC) of surfactant, electrostatic and hydrophobic interactions as well as polarity of the medium plays significant role in this phenomenon. The negative values of Gibbs energies of binding (∆G b ) and partition (∆G p ) predicts the feasibility and spontaneity of respective processes. Similarly negative values of ∆G m and ∆H m and positive values of ∆S m , calculated from conductometeric data, further, revealed the exothermicity, spontaneity and, thus, stability of system. The results, herein, have disclosed the strong interaction between dye and surfactant molecules. The dye-2 has been observed to be solubilized to greater extent, as compared to dye 1, due to strong interaction ith hydrophiles of CTAB and accommodation of its molecules in palisade layer of micelle closer to the micelle/water interface.

Influence of Ethylene Oxide Content in Nonionic Surfactant to the Hydrolysis of Reactive Dye in Silicone Non-Aqueous Dyeing System

Silicone reverse dyeing technology provides an important means of saving water and salts-free in the textile dyeing industry. The interactions between dyes and surfactants may influence the hydrolysis of dye during dyeing. In this investigation, the effect of ethylene oxide content in nonionic surfactant on the hydrolytic reaction of reactive dye was firstly investigated in a siloxane reverse emulsion dyeing system. Compared with no surfactants, the hydrolytic reaction of vinyl sulfone reactive dye was a slowdown when some nonionic surfactants were used during dyeing. Usually, the hydrophobic groups in nonionic surfactants were dodecyl chains but their polar head groups were different. The hydrolytic reaction of vinyl sulfone dye showed that the longer of EO (ethylene oxide) chains, the faster the hydrolytic reaction of vinyl sulfone dye. From the absorption spectrum of dye, it could be concluded that more of dyes would be solubilized into the formed micelles, and dye-surfactant complexes were adhered to the surface of micelles if the molecular structure of surfactant had a shorter EO chains. Furthermore, the intramolecular or intermolecular hydrogen bond could be formed between dye and surfactant, which would further influence the hydrolytic reaction of vinyl sulfone dye. However, the solubility of surfactant in siloxane non-aqueous media would decrease with the increase of EO chains. Meanwhile, the dispersion of dye was enhanced as well as the hydrolytic reaction of dye. From this investigation, some surfactant can be used to improve the fixation of reactive dye during dyeing. Furthermore, washing times after dyeing and the ecological problems can be decreased.

Physico-Chemical Studies of Glycine, L-Alanine, L-Phenylalanine and Glycylglycine in Aqueous Triton X-100 at Different Temperatures

The densities, ρ and viscosities, η of glycine (Gly), L-alanine (Ala), L-phenylalanine (Phe) and glycylglycine (Gly-Gly) in aqueous Triton X-100 (TX-100) solutions have been measured as a function of amino acid/peptide concentration at 298.15, 303.15, 308.15 and 313.15 K. The experimental data have been utilized to evaluate various thermodynamic parameters, viz., apparent molar volumes, V 2, partial molar volumes at infinite dilution, V 0 2, partial molar isobaric expansibilities, ϕ 0 2, partial molar volumes of transfer, Δ tr V 0 2 and A and B-coefficients of viscosity, respectively. The hydration numbers have also been calculated. The results have been discussed in terms of interactions taking place in the present systems. The structure-making/-breaking ability of the solute (amino acid/peptide) in the presence of surfactant, Triton X-100 has also been considered.

Conductivity Measurements as a Method for Studying Ionic Technical Grade Surfactants

The critical micellar concentrations (cmc) of cationic alkyltrimethylammonium bromides (C10TAB – C16TAB) and of anionic alkyl sulfates (SDS, technical grade Sulfopon 12G and Sulfopon 1214G) were determined using specific conductivity and surface tension measurements. While the cationic surfactants were purified, the anionic surfactants were used as received. In the former case, surface tension and conductivity measurements lead to the same cmc values. In the latter case, measuring the specific conductivities (bulk property) proved to be superior compared to measuring the surface tensions (surface property) because the presence of highly surface active impurities creates a pronounced minimum in the surface tension isotherm, which makes it impossible to determine an accurate value for the cmc. On the other hand, these impurities do not influence the conductivities, i. e. that the conductivities can be used to determine cmc values of impure and technical grade ionic surfactants, respectively. Moreover, an evaluation of the specific conductivities allows for the determination of the degree of micelle ionization (α) of the ionic surfactant solutions and thus provides additional useful information.