Abstract  The thermodynamic parameters of mixed micelle formation (Lambda(mic)G degrees, Lambda(mic)H degrees, Lambda(mic)S degrees) have been determined for a series of mixed micelles consisting of two isomeric hexanediols (1,2-hexanediol and 1,6-hexanediol) in sodium dodecylsulfate micellar solutions. The enthalpies of micellization were determined directly from isoperibol solution calorimetry. Gibbs energies and entropies of micelle formation were obtained from the application of the charged pseudo-phase model of micelle formation to the calorimetric critical micelle concentration values. The location of the alcohols in the micellar palisade layer has been determined from two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) experiments. The calorimetric titration data indicates that the placement of the hydroxyl groups on the six carbon backbone greatly affects the energetics of the micelle formation process. From the NMR data, the location of the cosurfactant in the micelle has been determined. These results indicate that the locus of solubilization affects the subtle balance of forces responsible for the formation of the mixed aggregates.

Abstract  The gemini surfactant N-N'bis(dimethyldodecyl)-1,4-butanediammonium dibromide (12-4-12) was synthesized and its critical micelle concentrations (CMCs) and degree of counterion dissociation (alpha) in aqueous solutions in the presence of alkanols viz ethanol, isomeric butyl alcohols, 1-hexanol and alkanediols (ethanediol, 1,4-butanediol, 1,2-hexanediol, 2,5-hexanediol 1,6-hexanediol, and 1,8-octanediol) determined from electrical conductivity are reported. While ethanol, ethanediol, 1,4-butanediol showed an increase in CMC, a decrease was seen for isomeric butyl alcohols, 1-hexanol, isomeric hexanediols and 1,8-octanediol. For butyl alcohols the CMC decrease showed the trend 1 degrees>2 degrees>3 degrees in C(6) diols, 1,2-hexanediol exerted more decrease as compared to 2,5-hexanediol and 1,6-hexanediol.The results are explained on the basis of the structure and hydrophobicity of alcohols that determine their effect as cosolvent or cosurfactant (partitioning in micelles). Two-dimensional nuclear overhauser enhancement spectroscopy (2D-NOESY) was used to examine the location for 1-butanol and 1,4-butanediol in micellar systems as representative additives from alkanols and alkanediols showing CMC decreasing and increasing effect respectively. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  Microemulsions (mu E) were prepared with palm fatty acid esters (PFAME) as solvents stabilised by fatty alcohol ethoxylates (hydrophilic-lipophilic balance, HLB value similar to 12.8), and 1,2 hexanediol as a co-surfactant. The effects of co-surfactant on the ternary phase systems were studied only at 10, 15, 20, 25, and 30% (w/w) of surfactant concentrations. The ratio of PFAME/water was chosen at 30:70 only. The mixtures were mixed vigorously and then kept at ambient temperature (25 degrees C) for few days. The emulsions (two-phase), mu E and liquid crystalline phases were observed using the polarised light. In addition, the physical stability (accelerated test/month at 45 degrees C),conductivity and viscosity for mu E solutions were measured. The effects of co-surfactant on the ternary phase systems for PFAME/non-ionic surfactant/water were constructed at 25 and 45 degrees C. The result showed that larger mu E region was formed with PFAME 1 than the PFAME 2 at 30:70 ratio of oil to water. The minimum concentration of surfactant for producing clear, low viscosity and thermodynamically stable mu E solutions was 10% (w/w) for both PFAME 1 and PFAME 2 at 25C. However, the concentration of co-surfactant used to produce mu E solutions was 12.5% for PFAME 1 but was 30% (w/w) for PFAME 2. Furthermore, the conductivity and viscosity measurements indicated types of mu E, that is, O/W or W/O formed.

Abstract  Microemulsions formed with water, isopropyl myristate, PHS-PEO-PHS polymeric surfactant, and alkanediol have been investigated using small-angle X-ray scattering (SAXS) and conductivity at 25 degreesC. Isopropyl myristate has a low solubility in water; however, this molecule has some polar character because of its ester group. The conductivities of samples with some added NaCl (used here to increase the conductivity sensitivity) are low, but compared to the conductivity of water/alkanediol mixtures, the values are high for most of the samples. The X-ray scattering curves show a correlation peak if the water content is high enough. A two-phase model for the invariant calculation fits the experimental results reasonably well provided that the partition of the oil between the polar and nonpolar phases is taken into account. This partition can be obtained from the ternary water/isopropyl myristate/alkanediol system, which has some mutual-solubility regions. A hard-sphere model can be fitted to the SAXS scattering data. The volume fractions fitted from this model deviate from the volume fractions of the low-polarity phase, indicating that the structure of most of the samples is of the bicontinuous type.

Abstract  Liquid-liquid equilibria for hexafluorophosphate ionic liquids with 1-alkyl-3-methylimidazolium family of cations: 1-butyl-3-methylimidazolium, [bmim](+), 1-hexy1-3-methylimidazolium, [hmim](+), 1-octyl-3methylimidazolium, [omim](+) with polyhydric alcohols: 1,2-ethanediol, 1.2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol have been measured using the cloud point method. The influence of different characteristics of alcohols and ILs, including cation alkyl chain length, alcohol chain length, and relative position of the both OH groups in alcohol were studied. In general, the same type of the phase behavior is observed in all cases showing upper critical solution temperature but the impact of the above-mentioned factors is highly diversified. (c) 2011 Elsevier B.V. All rights reserved.

Abstract  A straight-chain alcohol or diol additive in the mobile phase was used to modify and improve the HPLC separation of organic acids and bases. Incorporation of 2% 1-butanol, 1% 1,2-hexanediol, or 0.25% 1,2-octanediol into an aqueous mobile phase greatly improved the separation of alkane carboxylic acids on a silica C18 column, both in terms of separation time and peak shape. When 1.5% 1-hexanol, 0.09% 1-decanol or 0.01% 1-dodecanol was added to an acetonitrile-water (30:70) mobile phase, much sharper peaks and better resolution were obtained for aromatic bases separated on an underivatized polystyrene-divinylbenzene column. The mobile phase additive is believed to coat the stationary phase surface by a dynamic equilibrium. The coated surface is more hydrophilic and facilitates the efficient partitioning of analytes between the mobile and stationary phases.

Abstract  Droplet evaporation of multicomponent droplets is essential for various physiochemical applications, e.g., in inkjet printing, spray cooling, and microfabrication. In this work, we observe and study the phase segregation of an evaporating sessile binary droplet, consisting of a miscible mixture of water and a surfactantlike liquid (1,2-hexanediol). The phase segregation (i.e., demixing) leads to a reduced water evaporation rate of the droplet, and eventually the evaporation process ceases due to shielding of the water by the nonvolatile 1,2-hexanediol. Visualizations of the flow field by particle image velocimetry and numerical simulations reveal that the timescale of water evaporation at the droplet rim is faster than that of the Marangoni flow, which originates from the surface tension difference between water and 1,2-hexanediol, eventually leading to segregation.

Abstract  Some polyols show micellar behavior in aqueous solutions at concentrations greater than the critical micellar concentration (cmc). The 1,2-alkanediols (C(n)H(2n+2)O2 with n=5,6,7), the 1,2,3-alkanetriols (C(n)H(2n+2)O3 with n=7,8,9), and the geminated alkanetriols (C(n)H(2n+2)O3 with n=8 and 9) are investigated by microcalorimetric techniques. Only the 1,2-hexanediol (n=6), the 1,2,3-octanetriol (n=8), and the 2,2-dihydroxymethyl 1-heptanol (n=9) possess, in aqueous solutions, an organized structure above the critical micellar concentration (cmc). The 1,2-pentanediol (n=5) and the 1,2,3-heptanetriol (n=7) would form weak associations, whereas the 2,2-dihydroxymethyl 1-hexanol (n=8) does not form any associations even at large concentration. The 1,2-heptanediol (n=7), being only very slightly soluble even at a temperature of 30 degrees C, could not be studied. The 1,2,3-nonanetriol (n=9) is not soluble at temperatures between 20 and 35 degrees C. The critical micellar concentrations are determined by specific heat capacity methods. The passage from the dispersed environment to the organized environment gives a constant quantity of specific heat capacities (about 50 JK(-1)mol(-1)) only for the 1,2-hexanediol (n=6), the 1,2,3-octanetriol (n=8) and the 2,2-dihydroxymethyl 1-heptanol (n=9), which form true micelles. Structural effects of these systems are discussed.

Abstract  Legumes such as alfalfa (Medicago sativa L.), barrel medic (Medicago truncatula), white sweet clover (Melilotus alba) and fenugreek (Trigonella graecum), normally accumulate (-)-medicarpin and its malonated glucose conjugate as natural inhibitors of fungal pathogens. These plants also accumulate the biosynthetic precursor formononetin as well as the malonated glycoside. We were interested in developing a robust high-throughput method to quantitate the levels of these two isoflavonoids, both free and conjugated, in legume root extracts, for use in screening for mutant plants accumulating altered levels of these compounds. Capillary electrophoresis was examined as an alternative to current high-performance liquid chromatography (HPLC) methods to generate isoflavonoid profiles. The developed assay used micellar electrokinetic capillary chromatography (MEKC) to provide the required selectivity in complex root extracts. The addition of 1,2-hexanediol to the sodium dodecyl sulfate (SDS) electrolyte provided improved resolution of adjacent isoflavonoids. We examined the role of several factors including sample preparation, buffer composition, buffer pH, and organic component in the injected sample. The use of capillaries with longer path lengths were also examined to increase sensitivity. A comparison of results obtained using MEKC and HPLC showed good correlation in the relative amounts of the isoflavonoids studied.

Abstract  Aliphatic, linear dicarboxylic acids and branched dicarboxylic acids are the subject of this article. These dibasic acids are referred to by their trivial names, IUPAC system or by adding the suffix “dicarboxylic acid“ to the name of the hydrocarbon skeleton. For example a 10‐carbon atom dibasic acid is designated sebacic acid, decanoic or 1,8‐octane‐dicarboxylic acid. Physical and chemical properties of the most common dibasic acids are discussed. Manufacture and uses for glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic acid, brassylic acid and C‐19, C‐20, and C‐22 dicarboxylic acids are given. These diacids are intermediates for the manufacture of diesters, polyesters, and polyamides. These derivatives have many applications ,eg, as plasticizing agents, lubricants, heat‐transfer fuids, inks and coatings, insecticides. Azaleic acid is used in acne preparations. Toxicities and environmental concerns are also discussed.

Abstract  The study reports pig-skin permeation and skin accumulation of miconazole nitrate (MCZ) from positively charged microemulsions containing water, 1-decanol/1-dodecanol (2:1, w/w), lecithin and/or decyl polyglucoside at different weight ratios, propylene glycol, 1,2 hexanediol and a cationic charge-inducing agent (stearylamine (ST), L-alanine benzyl ester (ALAB) or cetyltrimethylammonium bromide (CTAB)). Zeta-potential values of the positively charged microemulsions ranged from 14.2 to 37.5 mV and mean droplet size from 6.0 to 16.8 nm. In vitro pig-skin permeation of MCZ after a single 24 h application was negligible for all microemulsions; accumulation from positively charged microemulsions was nearly twice that from their negatively charged counterparts. The increased accumulation might be ascribed to the interaction between positive microemulsive systems and negatively charged skin sites; no significant difference was observed among the various cationic charge-inducing agents. Skin accumulation from the microemulsion containing most lecithin was lower than those of other microemulsions; this was ascribed to the phase transformation from microemulsion to a liquid crystal system after skin contact. These results suggest that positively charged microemulsions could be used to optimize drug targeting without a concomitant increase in systemic absorption; ALAB, an ester of a natural aminoacid, is an appropriate cationic charge-inducing agent. (C) 2007 Elsevier B.V. All rights reserved.

Abstract  Microemulsions (mu E) were prepared with palm fatty acid methyl esters (PFAME) as solvents, and stabilised by ethoxylated non-ionic surfactants, i.e., Dehydol LS 7 and Dehydol LS 2 as S-A and S-B with the hydrophilic-lipophilic balance (HLB) values at similar to 12.8 and similar to 7.3, respectively. The co-surfactants chosen were 1,2-hexanediol, 1,2-butanediol, 1,2-ethanediol and glycerol. The effects of the co-surfactants on the partial ternary phase diagrams were studied at 10%, 15%, 20%, 25%, 30% and 40% (w/w) concentrations. The ratio of PFAME to water was either 25:75 or 50:50. The mixtures were agitated vigorously, and then kept at ambient temperature (25 degrees C) for one to two days. The emulsions (two-phase), the mu E and liquid crystalline phases were observed using polarised light. In addition, the physical stability of the mu E solutions was determined at 45 degrees C over a period of one month. The effects of the co-surfactants on the ternary phase systems for PFAME/non-ionic surfactants/water were studied and mapped out at 25 degrees C and 45 degrees C, respectively.

Abstract  Nickel supported on a variety of supports was evaluated in the batchwise hydrogenolysis of high-crystalline cellulose under hydrothermal conditions. The supports examined included Al2O3, kieselguhr, TiO2, SiO2, activated carbon (AC), ZnO, ZrO2 and MgO. All tested catalysts can effectively convert cellulose while the choice of supports plays a critical role in the product distribution and selectivity. The Ni catalysts favour the formation of industrially attractive 1,2-alkanediols such as 1,2-propanediol, ethylene glycol, 1,2-butanediol and 1,2-hexanediol. It was found that the bifunctional ZnO-supported Ni catalysts displayed superior activities and the best result was obtained on 20% Ni/ZnO which exhibited complete conversion of cellulose with up to 70.4% total glycol yields. The mechanism of the reaction involved was tentatively proposed by identifying the products formed.

Abstract  The aim of the current study was to investigate the effect of different co-surfactants on the phase behaviour of the pseudoternary system water:ethyl oleate:nonionic surfactant blend (sorbitan monolaurate/polyoxyethylene 20 sorbitan mono-oleate). Four aliphatic alcohols (1-propanol, 1-butanol, 1-hexanol and 1-octanol) and four 1,2-alkanediols (1,2-propanediol. 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol) were used. The co-surfactant-free system forms two different colloidal structures, a water-in-oil microemulsion (w/o ME) and lamellar liquid crystals (LC) and two coarse dispersions, water-in-oil (w/o EM) and oil-in-water (o/w EM) emulsions. Microemulsion region area (%ME), liquid crystalline region area (%LC), amount of amphiphile blend required to produce a balanced microemulsion (%AMPH) and amount of water solubilised (%W)were used as assessment criteria to evaluate the co-surfactants. Seven calculated physico-chemical descriptors were used to represent the different co-surfactants. 1-butanol, 1,2-hexanediol and 1,2-octanediol produced balanced MEs capable of solubilising a high percentage of both oil and water. A similarity was observed between the descriptors attributed to I-butanol and 1,2-hexanediol. The requirements of a co-surfactant molecule to produce a balanced microemulsion were: HLB Value 7.0-8.0, a carbon backbone of 4-6 atoms, percentage carbon of 60-65%, percentage oxygen of 20-30%, log P value 0.2-0.9 and log 1/S (S: aqueous solubility) close to zero. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract  Density and isobaric heat capacity per unit volume were determined for aqueous mixtures of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,2-hexanediol over the whole composition range in the temperature interval (283.15-313.15) K at atmospheric pressure. From these data, excess molar volumes and excess isobaric molar heat capacities were obtained. The comparison of experimental data with literature values shows quite good agreement, not only for absolute magnitudes, but also for excess quantities. Excess volumes are negative over the whole composition range and they become more ideal (less negative) as temperature increases. Excess isobaric molar heat capacity is mostly positive, although it is negative for some mixtures at several compositions and temperatures. Moreover, it was found that it presents a maximum at low mole fraction of the alcohol for most systems, as it was previously found for alkanol + water mixtures. As for temperature dependence, excess isobaric molar heat capacity increases with raising temperature in all cases. This increase is more pronounced for concentrated solutions of dialcohol, with the exception of the 1,2-hexanediol system. The obtained results are interpreted in terms of well-known arguments based on definition of excess magnitudes and chemical nature of the compounds. (C) 2013 Elsevier B.V. All rights reserved.

Abstract  Using biomass-derived ethylene glycol (bio-EG) to synthesize poly(ethylene terephthalate) (PET) is of notable significance for alleviating the dependence on fossil energy resources. Bio-EG readily contains a small amount of miscellaneous diols, which derive from the side reactions in the catalytic conversion of biomass. To disclose the effects of miscellaneous diols on the synthesis and properties of PET, EG feedstock containing four 1,2-diols, i.e., 1,2-propylene glycol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 0-10% concentrations was used for the synthesis of PET. The molecular weights, intrinsic viscosities, and thermal and mechanical properties of obtained PET materials were measured. It was found that when the overall content of miscellaneous diols in EG was lower than 5%, the molecular weights and thermal properties of the prepared PET materials were very similar to that of PET synthesized from pure EG. The miscellaneous diols were less likely to be incorporated into PET resin because of the steric hindrance of the alkyl group in diols to the esterification and polycondensation reactions. Instead, they preferred to undergo dehydration reactions to form low-boiling-point aldehydes and hemiacetals, which could be removed from the reaction system during the reactions. Three bio-EG samples at purities of 99.9, 98.5, and 95.8 wt % were used for the bio-PET synthesis. Transparent and colorless bio-PET samples were obtained, demonstrating that the presence of miscellaneous diols does not have negative effects on the color quality of PET. The physical properties of bio-PET prepared with bio-EG at a purity of higher than 98 wt % were nearly the same as those of PET derived from pure EG. At a lower bio-EG purity of 95.8 wt %, the tensile strength of the obtained bio-PET sample was slightly decreased. The comprehensive results of property characterization show that bio-PET materials prepared with bio-EG at purity higher than 95 wt % could be used as widely as the conventional petro-PET resin without notable deterioration in their performance.

Abstract  To study the potential for delayed Type IV dermal sensitivity of a new preservative system containing 1,2-hexanediol and caprylyl glycol, 200-subject repeat insult patch tests were performed with a 15% mixture of 1,2-hexanediol and caprylyl glycol (equal parts of the 2 ingredients) in carbomer gel and a cosmetic formulation at an actual use concentration. No delayed Type IV hypersensitivity reactions were observed.

Abstract  Atmospheric aerosol particles are often partially or completely composed of inorganic salts, such as ammonium sulfate and sodium chloride, and therefore exhibit hygroscopic properties. Many inorganic salts have well-defined deliquescence and efflorescence points at which they take up and lose water, respectively. Field measurements have shown that atmospheric aerosols are not typically pure inorganic salt, instead, they often also contain organic species. There is ample evidence from laboratory studies that suggests that mixed particles exist in a phase-separated state, with an aqueous inorganic core and organic shell. Although phase separation has not been measured in situ, there is no reason it would not also take place in the atmosphere. Here, we investigate the deliquescence and efflorescence points, phase separation and ability to exchange gas-phase components of mixed organic and inorganic aerosol using a flow tube coupled with FTIR (Fourier transform infrared) spectroscopy. Ammonium sulfate aerosol mixed with organic polyols with different O : C ratios, including 1,4-butanediol, glycerol, 1,2,6-hexanetriol, 1,2-hexanediol, and 1,5-pentanediol have been investigated. Those constituents correspond to materials found in the atmosphere in great abundance and, therefore, particles prepared in this study should mimic atmospheric mixed-phase aerosol particles. Some results of this study tend to be in agreement with previous microscopy experiments, but others, such as phase separation properties of 1,2,6-hexanetriol, do not agree with previous work. Because the particles studied in this experiment are of a smaller size than those used in microscopy studies, the discrepancies found could be a size-related effect.

Abstract  The micelle formation process for a typical anionic surfactant. sodium dodecyl sulfate, and a typical cationic surfactant, dodecyltrimethylammonium bromide, has been investigated in a series of mixed solvents consisting of different concentrations of isomeric hexanediols (1,2-hexanediol and 1,6-hexanediol) in water. The critical micelle concentrations and the degrees of counterion dissociation of the mixed micelles were obtained from conductance experiments. Luminescence probing experiments have been used to determine the concentration of micelles in solution and, hence, the micellar aggregation numbers of the surfactants in the mixed solvent systems. The alcohol aggregation numbers were determined by combining the partition coefficients (obtained using NMR paramagnetic relaxation enhancement experiments) with the micellar concentrations from the luminescence probing experiments. All these results are interpreted in terms of the difference in the interaction of the isomeric hexanediols with the surfactant as a function of the position of the hydroxyl groups on the six-carbon chain of the alcohol.

Abstract  Long chain aliphatic 1,2-diols like 1,2-hexanediol and 1,2-octanediol can be converted to the corresponding alpha-hydroxy-alkanoates with total chemoselectivity, in an oxidation catalyzed by an aqueous gold sol under O-2 atmosphere. The sol is stabilized with poly(vinylalcohol), and the reaction is performed in alcohol solvents. Two methods are proposed for the efficient recycling of the colloidal Au catalyst. Firstly a solvent-resistant membrane filtration can be applied. As the membrane material, poly(dimethylsiloxane) is chosen. Secondly, in appropriate conditions, the reaction proceeds in the liquid biphasic mode, and the aqueous Au sol can be recycled by phase separation. Using either of both approaches, the colloidal stability and catalytic activity can be preserved over several recycles.

Abstract  Background: Traditional preservation systems currently used in cosmetic and skin care products are safe and effective. New ingredients with similar efficacy are continually being introduced to fulfill this function. Objective: To study the potential for delayed type IV allergic hypersensitivity and irritation of a new preservative system containing 1,2-hexanediol and caprylyl glycol. Methods: A 200-subject repeat insult patch test (RIPT) was performed. A 15% mixture of 1,2-hexanediol and caprylyl glycol (equal parts of the two ingredients) in carbomer gel was placed under a series of 9 continuous occlusive induction patches, each 48 hours in duration. Three induction patches were applied each week, for a total of 3 weeks. Following a 10-day rest period during which no patches were applied, a single challenge application using the same mixture was applied and left on for 48 hours and read at 48 and 72 hours postapplication. A cosmetic formulation containing this same preservation system at an actual use concentration was tested by the same RIPT protocol. Results: Two hundred and twelve subjects completed the study. One hundred and sixty-eight were female and 44 were male ranging in age from 18 to 70 years. No reactions were seen during the induction or challenge phases. An additional 212 subjects were enrolled in a separate RIPT that evaluated the cosmetic formulation containing the same preservation system. No delayed type IV allergic hypersensitivity or irritation reactions were observed. Conclusion: A new preservative system utilizing 1,2-hexanediol and caprylyl glycol did not induce delayed type IV allergic hypersensitivity or irritation in human subjects.

Abstract  A study has been made of the acetoxylation of 1-hexene and cyclohexene in the presence of PdCl42- and a nitrate-iodate reoxidative system ensuring high yields of the corresponding acetoxyalkanes. It has been established that a binuclear pi-olefinic bridge-type palladium complex is a catalytically active particle. It is assumed that the mechanisms of formation of 1,2-hexanediol monoacetate and diacetoxycyclohexane differ at the final stage of transformation of the acetoxonium ion. Acetoxylation is retarded by the reaction products, which screen the coordination sphere of palladium.

Abstract  Aqueous dilute solutions of 2-butoxyethanol, 1,2-hexanediol, tert-butanol, 1-pentylamine and 1-butylamine are analized through the dynamic light scattering technique. The mutual diffusion coefficient is determined against amphiphile composition, showing, in all cases, clear minima in the dilute region. Using the Stokes-Einstein relation, the mean size of the aggregates is also obtained as a function of mole fraction. For enough concentrated solutions, structures in the range 2-20 angstrom are observed. It is found that both their size and the minimum amphiphile mole fraction for which aggregation is observed are strongly correlated with the hydrophobic character of the amphiphile. (C) 2017 Elsevier B.V. All rights reserved.