Conductometric study of the mixing behaviour of sodium benzoate and salicylate with an anionic surfactant sodium lauroylsarcosinate

Effects of two anionic hydrotropes – sodium benzoate (NaBz) and sodium salicylate (NaSal) – on the mixed-micelle formation with an amino-acid-based surfactant – sodium lauroylsarcosinate (SLS) – in water were investigated by the conductometric method. Specific conductivity was measured for SLS/NaBz/water and SLS/NaSal/water systems to determine the critical micelle concentration (cmc). Using the regular solution theory for non-ideal mixing, the pairwise interaction parameter, β₁₂, and micellar composition, χ, were estimated in the mixed micelle. The cmc values of the surfactant–hydrotropes mixtures were generally lower than those predicted from the ideal mixing theory. The β₁₂ values are generally negative for the two systems at all mole fractions with an average value of ?2.83 for the SLS/NaBz and ?3.31 for SLS/NaSal systems, respectively, indicative of a strong attractive interaction between the SLS/NaBz and SLS/NaSal mixed micelle. The calculated thermodynamic parameters of micellisation all indicated spontaneity in mixed-micelle formation for the systems studied.     

Alkyl Polyglycosides—Properties and Applications of a new Class of Surfactants

A new generation of nonionic surfactants that are widely applicable and simultaneously ecologically compatible has been developed in the alkyl polyglycosides. Their production from the renewable resources glucose and fatty alcohol and their ultimate biodegradation into carbon dioxide, water, and assimilated bacterial biomass is an example for a closed cycle. As a result of their physico-chemical properties and ecotoxicological evaluation, they have become very important as high-performance components of detergents and cosmetic preparations.     

Integrated Conversion of Lignocellulosic Biomass to Bio-Based Amphiphiles using a Functionalization-Defunctionalization Approach

Concerns over the sustainability and end-of-life properties of fossil-derived surfactants have driven interest in bio-based alternatives. Lignocellulosic biomass with its polar functional groups is an obvious feedstock for surfactant production but its use is limited by process complexity and low yield. Here, we present a simple two-step approach to prepare bio-based amphiphiles directly from hemicellulose and lignin at high yields (29 % w/w based on the total raw biomass and >80 % w/w of these two fractions). Acetal functionalization of xylan and lignin with fatty aldehydes during fractionation introduced hydrophobic segments and subsequent defunctionalization by hydrogenolysis of the xylose derivatives or acidic hydrolysis of the lignin derivatives produced amphiphiles. The resulting biodegradable xylose acetals and/or ethers, and lignin-based amphiphilic polymers both largely retained their original natural structures, but exhibited competitive or superior surface activity in water/oil systems compared to common bio-based surfactants.     

Order and chaos in soft condensed matter

Soft matter, like colloidal suspensions and surfactant gels, exhibit strong response to modest external perturbations. This paper reviews our recent experiments on the nonlinear flow behaviour of surfactant worm-like micellar gels. A rich dynamic behaviour exhibiting regular, quasi-periodic, intermittency and chaos is observed. In particular, we have shown experimentally that the route to chaos is via Type-II intermittency in shear thinning worm-like micellar solution of cetyltrimethylammonium tosylate where the strength of flow-concentration coupling is tuned by the addition of sodium chloride. A Poincaré first return map of the time series and the probability distribution of laminar length between burst events show that our data are consistent with Type-II intermittency. The existence of a ‘Butterfly’ intensity pattern in small angle light scattering (SALS) measurements performed simultaneously with the rheological measurements confirms the coupling of flow to concentration fluctuations in the system under study. The scattered depolarised intensity in SALS, sensitive to orientational order fluctuations, shows the same time-dependence (like intermittency) as that of shear stress.     

Ionic liquids in microemulsions

Ionic liquids (ILs) are being increasingly studied in many different chemical application areas, particularly in green solvent applications that are extending into microemulsion applications. We summarize herein these initial microemulsion formulations and applications where ILs are used as oil substitutes, water substitutes, co-surfactants (additives), and surfactants.     

Amphiphilic Heterografted Molecular Bottlebrushes with Tertiary Amine-Containing Side Chains as Efficient and Robust pH-Responsive Emulsifiers

By combining the unique characteristics of molecular bottlebrushes (MBBs) and the properties of stimuli-responsive polymers, we show that MBBs with randomly grafted poly(n-butyl acrylate) and pH-responsive poly(2-(N,N-diethylamino)ethyl methacrylate) (PDEAEMA) side chains are efficient and robust pH-responsive emulsifiers. Water-in-toluene emulsions were formed at pH 4.0 and disrupted by increasing the pH to 10.0. The emulsion generation and disruption was reversible over the ten cycles investigated, and the bottlebrushes remained intact. The exceptional emulsion stability stemmed from the high interfacial binding energy of MBBs, imparted by their large molecular size and Janus architecture at the interface, as evidenced by the interfacial jamming and wrinkling of the assemblies upon reducing the interfacial area. At pH 10.0, PDEAEMA became water-insoluble, and the MBBs desorbed from the interface, causing de-emulsification. Consequently, we have shown that the judicious design of MBBs can generate properties of particle emulsifiers from their large size, while the responsiveness of the MBBs enables more potential applications.     

Minimising oil droplet size using ultrasonic emulsification

The efficient production of nanoemulsions, with oil droplet sizes of less than 100 nm would facilitate the inclusion of oil soluble bio-active agents into a range of water based foods. Small droplet sizes lead to transparent emulsions so that product appearance is not altered by the addition of an oil phase. In this paper, we demonstrate that it is possible to create remarkably small transparent O/W nanoemulsions with average diameters as low as 40 nm from sunflower oil. This is achieved using ultrasound or high shear homogenization and a surfactant/co-surfactant/oil system that is well optimised. The minimum droplet size of 40 nm, was only obtained when both droplet deformability (surfactant design) and the applied shear (equipment geometry) were optimal. The time required to achieve the minimum droplet size was also clearly affected by the equipment configuration. Results at atmospheric pressure fitted an expected exponential relationship with the total energy density. However, we found that this relationship changes when an overpressure of up to 400 kPa is applied to the sonication vessel, leading to more efficient emulsion production. Oil stability is unaffected by the sonication process.     

丁基罗丹明B-表面活性剂体系荧光光谱法测定人血清蛋白

研究了阳离子染料丁基罗丹明 B在阴离子表面活性剂十二烷基苯磺酸钠存在时的吸收光谱和荧光性能 ,发现随蛋白质浓度增大荧光强度逐渐增强 ,在一定范围内增强程度与蛋白质浓度成正比 ,据此建立了一种测定人血清蛋白的新方法 ,线性范围 0— 6 .0 mg·L-1 ,检出限为 4 .4 μg/ L。用于合成样品测定 ,结果令人满意。     

Role of cetyltrimethylammonium bromide (cationic surfactant) on the tryptophan–MnO4 reaction

Upon addition of permanganate to a solution of tryptophan (Trp), yellow-brown color species appears within the time of mixing of tryptophan in absence and presence of cetyltrimethylammonium bromide (CTAB), which was stable for some days. Spectroscopic and kinetic evidences suggest the formation of water-soluble colloidal MnO₂ as the most stable reduction product of MnO₄⁻. Carbon dioxide and ammonia are not formed as the oxidation products. Carbon–carbon double bond of indole moiety of Trp is responsible for the fast reduction of permanganate. Cetyltrimethylammonium bromide catalyses the permanganate oxidation of Trp with a rate enhancement of ca. 200-fold. Sub- and postmicellar catalytic effect of CTAB ascribed to the association/incorporation/solubilization of both reactants (MnO₄⁻ and Trp) with the CTAB aggregates and into the Stern layer of cationic micelles. Quantitative kinetic analysis of the rate constant–[CTAB] data has been performed on the basis of modified pseudo-phase model of the micelles. A comparison was made of the oxidation rates of different amino acids by permanganate. The order of the effectiveness was as follows: tryptophan  tyrosine  phenylalanine.     

Scattering from polymer-like micelles

Polymer-like micelles are analogs to polymer solutions and provide an exciting class of materials for both applications and fundamental understanding of polyelectrolyte systems. Small angle neutron and X-ray scattering have been key to the characterization of these materials from the first observations of linear micelle growth. As new materials are developed, these techniques continue to be utilized and combined with other analytical tools to characterize the length and time scales of polymer-like micelle behavior. Recent reports on the use of small-angle scattering to characterize polymer-like and wormlike micelles are reviewed, with focus on new materials, improvements in analytical approaches and anisotropic structures.