Kinetics of vesicle formation

 The kinetics of vesicle formation from a hydrotrope (sodium xylenesulfonate) solution of a surfactant (Laureth 4) is studied by the use of a stopped-flow apparatus combined with a dynamic light scattering device to determine vesicle size in the system. The hydrotrope system studied presents a system with a high surfactant solubilization combined with vesicle formation simply by dilution with water. The kinetic results show a single exponential decay time. The kinetic analysis indicates that the vesicles are formed from a molecular solution which resulted from the shear in the stopped-flow device and grow by monomeric association. Received: 1 October 1996 Accepted: 22 November 1996     

The Hydrotrope Action of Vitamin C

The effects of vitamin C are determined in the oil-in-water(0/ W) and water-in-oil(W/ 0) microemulsion regions of CTAB/ pentanol/ p-xylene/ H20 system. The addition of Vc joins the O/ W and W/ O areas in the phase diagram and expands the bicontinous region by reducing the lamellar liquid crystal one. The results show that the “ coupling action” of Vc is in fact a structural transition from lamellar crystal to isotropic phase with W/ O, O/ W and bicontinous structure.     

Hydrotropic Behavior of Sodium Salicylate in Presence of Additives

It is well known that, like surfactants aggregating at a certain concentration (called critical micelle concentration, CMC), hydrotropes also have minimum hydrotrope concentration (MHC). However, unlike surfactant CMC, this MHC value is usually very high, thereby reducing their application. In this paper we report the results of conductivity and viscosity measurements with a well known hydrotrope sodium salicylate (NaSal) solutions in presence and absence of additives (propanol, PrOH; butanol, BuOH; pentanol, PeOH and tetrabutylammonium bromide, Bu₄NBr). We have found that MHC value of NaSal decreases in presence of additives. Alcohols increase the hydrophobic interactions and decrease the MHC while Bu₄NBr, in addition to ameliorating the hydrophobic interactions, reduces the charge on head groups and MHC decreases more steeply in its presence. Increased solubility of riboflavin in NaSal containing the above additives corroborates the results.     

Formulating Middle Phase Microemulsions Using Extended Anionic Surfactant Combined with Cationic Hydrotrope

The phase behavior of systems containing sodium alkyl polypropylene oxide sulfate with equimolar ratio of polypropylene oxide ammonium chloride was determined as a function of salt concentration and alkane carbon number at ambient temperature. Visual inspection as well as cross polarizers were used to detect anisotropy. Solubilization ratios for oil and brine in the middle phases were measured and used to calculate the interfacial tension (IFT) between the microemulsion and oil or brine. The fish diagram is presented showing a minimum amount of 0.20 wt% surfactant needed to form the middle phase. Swelling increases with decreasing the alkane carbon number of the oil. Ultra low IFT values were predicted for the systems investigated.     

Hydrotrope induced synthesis of 1,8-dioxo-octahydroxanthenes in aqueous medium

Abstract

Hydrotrope induced synthesis of 1,8-dioxo-octahydroxanthenes from aromatic aldehydes and dimedone/1,3-cyclohexadione in aqueous medium is reported. The remarkable features of the new procedure are high conversions, shorter reaction times, cleaner reaction profiles, and simple experimental and work-up procedures.     

Minimum Hydrotrope Concentration Behavior of Aqueous Solution of Sodium Salicylate in Presence of Additives

Hydrotropes are regaining importance in the currently blossoming field of self-organizing molecular systems. Their hydrophile-lipophile balance being on the higher side, their water solubility is significantly more than that of traditional surfactants, and, yet, they provide a sequestered niche or microenvironment for the solubilizate. Hydrotropes start aggregating at a certain concentration known as minimum hydrotrope concentration (MHC). The MHC values fall in the molar range because of which hydrotropes applications are reducing. In this article, the effect of various additives such as alcohols, electrolytes, surfactants, amines, and organic compounds on the behavior of sodium salicylate (NaSal) was investigated using viscosity measurement.     

Microemulsion Phase Behavior of Aerosol-OT Combined with a Cationic Hydrotrope in the Dilute Region

The phase behavior of systems containing minimum amounts of sodium bis (2-ethylhexyl) sulfosuccinate with equimolar ratio of tetra ethyl ammonium chloride were studied as a function of salt concentration and alkane carbon number at ambient temperature. Visual inspection as well as cross polarizers were used to detect anisotropy. Solubilization ratios for oil and brine in the middle phases were measured and used to calculate the interfacial tension. Ultra-low interfacial tension values were predicted for the systems containing heptane, octane and nonane as model oil. Different phase behavior was observed for systems with higher alkane number.     

Small angle neutron scattering studies of mixed micelles of sodium cumene sulphonate with cetyl trimethylammonium bromide and sodium dodecyl sulphate

The aqueous solutions of sodium cumene sulphonate (NaCS) and its mixtures with each of cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) are characterized by small angle neutron scattering (SANS). NaCS when added to CTAB solution leads to the formation of long rod-shaped micelles with a dramatic increase in the CTAB aggregation number. Its addition to SDS on the other hand results in the formation of smaller mixed micelles where part of SDS molecules in the micelle is replaced by NaCS molecules.      

Eco-conception of Highly Salt-Tolerant Alkyl Ether Carboxylate Hydrotropes with a Glyceryl Spacer

New alkyl ether carboxylates with a glyceryl spacer instead of ethylene glycol units have been synthesised using environmentally friendly methodology. A cascade synthesis of acetalisation and hydrogenolysis was developed to obtain products containing an alkyl chain linked to a glycerol unit bearing a polar carboxylate head. These products were methylated by using trimethyl phosphate to observe the influence of a free or methoxylated alcohol on the physicochemical properties. Finally, saponification gave the carboxylate anionic group of the new hydrotropes. Studying the amphiphilicity, the tolerance to sodium and calcium ions, and the solubilising power of these bio-based ionic/nonionic hydrotropes has shown that they exhibit significantly improved application properties compared to similar petro-based hydrotropes.