Persistence of the Antibacterial and Antiviral Effects after Skin Cleansing ~A New Approach to Suppress the Contact Infection~.

Handwashing represents an important personal hygiene measure for preventing infection. Herein, we report the persistence of antibacterial and antiviral effects after handwashing with fatty acid salt-based hand soap. To this end, we developed a new in vitro test method to measure persistence, utilizing coacervation formed by anionic surfactants and cationic polymers to retain highly effective soap components against each bacterium and virus on the skin. Coacervation with fatty acid salts and poly diallyldimethylammonium chloride (PDADMAC) as a cationic polymer allowed the persistence of antibacterial and antiviral effects against E. coli, S. aureus, and influenza virus even 4 h after handwashing. Furthermore, we confirmed an increase in the number of residual components effective against each bacterium and virus on the skin. In summary, the current findings describe an effective approach for enhancing the protective effects of handwashing.

Effect of Micellar Shape on Viscoelastic Behavior and Gel Network Structure of Hydrogel Formed by Surfactant-mediated Gelation Using Glutamic-acid-based Organogelator.

Surfactant-mediated gelation (SMG) is a technique used to form hydrogels by solubilizing water-insoluble low-molecular-weight organogelators in surfactant micelles. In this study, we investigated the viscoelastic behavior of SMG hydrogels and the effect of micellar shape on their gel network structure using a glutamic acid-based organogelator. Stress-strain curves obtained from static viscoelasticity measurements showed that a wormlike micelle-mediated gel (W-SMG) exhibited a higher stress than a spherical micelle-mediated gel (S-SMG). From the viscosity-shear rate curve (flow curve), we inferred that the SMG gel exhibited a shear thickening behavior, particularly W-SMG. Microscopic observations revealed that W-SMG formed a denser and more uniform gel network than S-SMG when subjected to strong shearing. W-SMG showed remarkable adhesiveness and a significantly higher tensile normal stress than S-SMG. The storage modulus and loss modulus of W-SMG and the wormlike micellar solution obtained from frequency sweep measurements of the dynamic viscoelasticity were analyzed by Maxwell fitting. The wormlike micellar solution produced a good fit with the single Maxwell model, whereas W-SMG produced the best fit with the generalized Maxwell model comprising two Maxwell elements. From the relaxation time characteristics obtained from the Maxwell model, W-SMG was found to be a viscoelastic material coexisting with a structure having a short relaxation time derived from the gel network and a long relaxation time derived from the wormlike micelle. Under the oscillation strain measured by a rheometer, W-SMG showed a greater normal stress than the wormlike micellar solution, indicating a significant Weissenberg effect.

Hydrogel Formation by Glutamic-acid-based Organogelator Using Surfactant-mediated Gelation.

Hydrogels formed by low-molecular-weight gelators have reversible sol-gel transition and responsiveness to various stimuli, and are used in cosmetics and drug applications. It is challenging to obtain hydrogels using novel gelators because subtle differences in their molecular architecture affect gelation. Organogelators (which form organogels) are insoluble in water, and their use as hydrogelators has not previously been considered. However, a surfactant-mediated gelation method was reported in which organogelators were solubilized in water by surfactants to form hydrogels using 12-hydroxyoctadecanoic acid. To investigate whether this method can be applied with other organogelators, the formation of hydrogel using a glutamic-acid-based organogelator was studied here. Hydrogels were formed by solubilizing 1:1 mixtures of glutamate-based organogelators, N-lauroyl-L-glutamic acid dibuthylamide, and N-2-ethylhexanoyl-L-glutamic acid dibutylamide in aqueous micellar solutions of anionic surfactant (sodium lauroyl glutamate) and cationic surfactant (cetyltrimethylammonium chloride). The minimum gelation concentration of the hydrogel was ~0.2-0.6 wt%. By changing the molar fraction of cetyltrimethylammonium chloride in the mixed surfactant, either spherical or wormlike micelles were formed. The hydrogel with wormlike micelles had a higher sol-gel transition temperature than that with spherical micelles and formed fine self-assembled fibrillar networks. Additionally, the hydrogel with the spherical micelles was elastic, whereas that with wormlike micelles was viscoelastic, suggesting that networks of the organogelators and wormlike micelles coexisted in the hydrogel from the wormlike micellar solution. Moreover, the hydrogel suppressed the reduction in the storage modulus at higher temperatures compared with the micellar aqueous solution, indicating that the elastic properties of the organogelator networks were maintained at high temperatures. The gel fibers of the hydrogel partially formed a loosely aggregated structure as the temperature increased, the fibers bundled via hydrophobic interactions, and new cross-linking points formed spontaneously. This phenomenon corresponded with an inflection point in the temperature-dependent storage modulus of the hydrogel.

Effect of Adding Lecithin and Nonionic Surfactant on α-Gels Based on a Cationic Surfactant-Fatty Alcohol Mixture.

α-Gels are often used as base materials for cosmetics and hair conditioners. α-Gel-based commercial products typically contain many types of additives, such as polymers, electrolytes, oily components, and other surfactants, in addition to the three basic components. However, few systematic studies have been conducted on the effect of such additives on α-gels. In this study, we chose surfactant as an example to initiate the effect of such additives on the structure and rheological properties of α-gel samples formulated using cetyl alcohol (C16OH) and cetyltrimethylammonium chloride (CTAC). Optical microscopy analysis demonstrated that the size of the vesicles in the α-gel samples in this study was decreased via the addition of hydrogenated soybean lecithin (HSL) and penta(oxyethylene) cetyl ether (C16EO5), a nonionic surfactant, to them. Rheological measurements revealed that at high C16OH/CTAC ratios, the viscosity and yield stress of the α-gel samples decreased owing to the addition of surfactants to them. Conversely, at low C16OH/CTAC ratios, the opposite tendency was observed. Small-angle X-ray scattering analysis indicated that for the α-gel samples with high C16OH/CTAC ratios, the addition of HSL or C16EO5 to them decreased the interlayer spacing of their lamellar bilayer stack, which led to the changes in the rheological properties of the α-gel samples.

Effect of the Cationic Head Group on Cationic Surfactant-Based Surfactant Mediated Gelation (SMG).

The surfactant-mediated gelation (SMG) method allows us to formulate hydrogels using a water-insoluble organogelator. In this study, we formulated hydrogels using three cationic surfactants, hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC), and hexadecylpyridinium chloride (CPC)] and an organogelator (12-hydroxyoctadecanoic acid (12-HOA), and studied their structures and mechanical properties. A fiber-like structure similar to that found in the 12-HOA-based organogels was observed by optical microscopy. Small- and wide-angle X-ray scattering profiles showed Bragg peaks derived from the long- and short-spacing of the crystalline structures in the gel fibers and a correlation peak from the surfactant micelles in the small-angle region. Furthermore, the formation of micelles in the hydrogels was confirmed by UV-vis spectroscopic measurements of the gel samples in the presence of Rhodamine 6G. We concluded that the hydrogels prepared by the SMG method in the present systems are orthogonal molecular assembled systems in which two different molecular assembled structures coexist. Among the three surfactant systems, the CTAB system presented the lowest critical gelation concentration and highest sol-gel transition temperature and viscoelasticity. These differences in gel fiber formation and gel properties were discussed from the viewpoint of the degree of solubilization of the gelator molecules in micelles coexisting with gel fibers and diffusion of the gelator molecules in the gel formation process.

Coacervation in Cationic Polyelectrolyte Solutions with Anionic Amino Acid Surfactants.

Coacervates formed by cationic polyelectrolytes and anionic surfactants are utilized to improve the user's tactile perception of shampooing hair during washing and after drying. In this study, we investigated the formation and structure of coacervates in aqueous systems containing anionic amino acid surfactants. The phase behaviors at constant temperature were investigated in aqueous systems combining cationic polyelectrolyte JR-400 with potassium cocoyl glutamate (CoGluK) or potassium cocoyl glycinate (CoGlyK) for a qualitative depiction of coacervate formation. The composition range of coacervate formation varied with the hydrophilic group of the surfactant. The surface tension was measured at different surfactant concentrations and constant polyelectrolyte concentration. The surface tension behavior revealed the critical association concentrations and critical micelle concentrations, indicating that coacervate was produced via complex formation through electrostatic interaction between opposite charges. Optical microscopy and small-angle X-ray scattering measurements revealed that the coacervates were composed of fibrous aggregates, a few microns thick, and those formed in the CoGlyK system had thicker fibers.

Formulation of Bicelles Based on Lecithin-Nonionic Surfactant Mixtures.

Bicelles have been intensively studied for use as drug delivery carriers and in biological studies, but their preparation with low-cost materials and via a simple process would allow their use for other purposes as well. Herein, bicelles were prepared through a semi-spontaneous method using a mixture of hydrogenated soybean lecithin (SL) and a nonionic surfactant, polyoxyethylene cholesteryl ether (ChEO10), and then we investigated the effect of composition and temperature on the structure of bicelles, which is important to design tailored systems. As the fraction of ChEO10 (XC) was increased, a bimodal particle size distribution with a small particle size of several tens of nanometers and a large particle size of several hundred nanometers was obtained, and only small particles were observed when XC ≥ 0.6, suggesting the formation of significant structure transition (liposomes to bicelles). The small-angle neutron scattering (SANS) spectrum for these particles fitted a core-shell bicelle model, providing further evidence of bicelle formation. A transition from a monomodal to a bimodal size distribution occurred as the temperature was increased, with this transition taking place at lower temperatures when higher SL-ChEO10 concentrations were used. SANS showed that this temperature-dependent size change was reversible, suggesting the SL-ChEO10 bicelles were stable against temperature, hence making them suitable for several applications.

Hydrogelation with a water-insoluble organogelator - surfactant mediated gelation (SMG).

The low-molecular-weight gelator (LMG) 12-hydroxyoctadecanoic acid (12-HOA) is insoluble in water, but can be solubilized in surfactant micelles. We therefore solubilized 12-HOA at 80 °C in an aqueous solution of cetyltrimethylammonium bromide (CTAB) containing spherical micelles. On cooling this system down to room temperature, a hydrogel is obtained. We will refer to this process as "surfactant-mediated gelation" (SMG). The hydrogels were formed at a lower 12-HOA concentration when sodium salicylate (NaSal) was added to the CTAB system, which induced the formation of wormlike micelles. Hydrogels obtained by SMG from spherical and wormlike micelles are referred to as gelled micellar phases (GMs) and gelled wormlike micellar phases (GWLMs), respectively. Optical microscopy and transmission electron microscopy (TEM) showed that 12-HOA forms self-assembled fibrillar networks (SAFiNs) in both GMs and GWLMs. The sol-gel transition temperature, Tsol-gel, of the GWLM samples was higher than that of the GM samples. Dynamic rheological measurements revealed gel properties (G' > G'' at all angular frequencies) for both gels; however, a higher viscoelasticity was observed for the GWLM samples, which in turn, was reflected in the higher Tsol-gel. Small- and wide-angle X-ray scattering (SWAXS) showed that micelles and gel fibers coexist in the GM and GWLM samples. Our study demonstrates the gelation of aqueous micellar solutions with water-insoluble LMGs.

Catastrophic Emulsion Inversion Process of Highly Viscous Isosorbide Biobased Polyester Monitoredin situ by Torque and Light Backscattering.

Highly viscous hydrophobic isosorbide biobased polyester O/W emulsions are prepared through catastrophic phase inversion. The process is followed in situ with two different methods: torque and light backscattering (LBS). Considering high viscosity of the system, only discontinuous conductivity monitoring is performed for comparison. Torque and LBS allow to highlight the emulsion inversion point (EIP) with relatively close water weight fraction values (fw≈0.20). The torque and LBS signals are rather noisy before inversion (evolution of different structures) and more smooth after phase inversion (continuous aqueous phase). Torque gives a more macroscopic information, representative of the global state of the dispersion. Consistent conductivity and torque measurements suggest indeed an inversion pathway through multiple o/W/O emulsions leading to multiple complex structures before getting continuous aqueous final emulsion. This hypothesis is confirmed with continuous LBS monitoring and microscopic observations. LBS signal seems more complete because it combines the information of conductivity and torque and allows to clearly follow in situ the inversion from the beginning to the end of the process.

Demonstration of a Novel Charge-Free Reverse Wormlike Micelle System.

We demonstrate a novel charge-free reverse wormlike micelle (RWLM) consisting of a ternary mixture of a nonionic amphiphilic block copolymer, fatty acid alkyl ester oil, and water under ambient conditions. Nonionic amphiphile tetra-[poly(oxyethylene)-poly(oxybutylene)]pentaerythrityl ether (TEBPE) self-assembled into spheroid-type micelles in nonaqueous media isopropyl myristate (IPM) with viscosity comparable to that of IPM. The addition of water increases viscosity only slightly up to a certain concentration of water and then drastically, demonstrating the sphere-to-wormlike micelle transition as confirmed by small-angle X-ray scattering. Further increase in water decreases the viscosity after attaining a maximum value. The zero shear viscosity (η0) of the 10 wt % TEBPE/IPM system reached the maximum at 2.6 wt % water and ca. 56 Pa·s, which is ∼fivefold higher than that of water. Dynamic rheological measurements on the highly viscous solutions confirmed the viscoelastic behavior and could be described by the Maxwell model. Conductivity, measured in the presence of a conductive probe, 1-ethyl-3-methylimidazolium tetrafluoroborate, was found to be higher for viscous samples compared to the nonviscous samples, suggesting the static percolation caused by the RWLM formation. Decrease in η0 and conductivity beyond a maximum suggests the shortening of reverse micelles. A similar behavior has been observed in other fatty acid alkyl ester oils of different alkyl chain lengths. Note that most of the RWLM systems previously reported are based on phosphatidylcholine (PC). Formulation and structure-properties related to non-PC-based RWLMs have been rarely explored. Non-PC-based RWLMs using chemically stable and low-cost synthetic molecules can be applied not only in pharmaceuticals and cosmetics but also in a wide range of applications including drag reduction agents for nonaqueous fluids and as a template for nanomaterial synthesis.

Cholesterol-Induced Formation of Liquid Ordered Phase-Like Structures in Non-Phospholipid Systems.

The formation of liquid ordered (Lo) phase-like structures in stearyltrimethylammonium chloride/cholesterol/1,3-butanediol/water and hepta(oxyethylen) octadecyl ether/cholesterol/1,3-butanediol/water systems was investigated. Differential scanning calorimetry and X-ray scattering measurements confirmed that Lo phase-like structures were formed in both surfactant/cholesterol systems, similar to the lysophospholipid/cholesterol system. It was revealed that the concentration of cholesterol at which only Lo phase-like structures are formed increases in the order stearyltrimethylammonium chloride < lysophospholipid < hepta(oxyethylen) octadecyl ether. In addition, for both surfactants, the interlayer spacing, d, was larger for Lo phase-like structures than for α-gel structures. These results suggest that the ionicity and structure of the hydrophilic group of each surfactant play important roles.

Gelling Lamellar Phases of the Binary System Water-Didodecyldimethylammonium Bromide with an Organogelator.

Does the presence of a gel network influence the properties of a lyotropic liquid crystal? Does the replacement of oil by a lyotropic liquid crystal influence the properties of an organogel? To answer these questions we study gelled lyotropic liquid crystals (LLC). In the present study we show that it is possible to gel the lamellar phase of the binary system water-didodecyl dimethylammonium bromide (2C12DAB) with the organogelator 12-hydroxyoctadecanoic acid (12-HOA). We compare various properties of the gelled LLC phases with the "parent systems", i.e., with the binary organogel consisting of n-decane-12-HOA and with the nongelled LC phases, respectively. Optical and electron microscopy, differential scanning calorimetry (DSC), rheometry, as well as small and wide-angle X-ray scattering (SWAXS) proved the coexistence of an Lα phase and a 12-HOA gel network in the gelled Lα phase. However, a small influence of the Lα phase on the gel properties was seen, namely slightly lower sol-gel transition temperatures and viscoelastic moduli of the gelled Lα phase compared to the binary gel. On the other hand, the presence of the gel also has an influence on the Lα phase: the interlayer spacing of the surfactant bilayers in the gelled Lα phases is slightly larger compared to the nongelled Lα phases, which is due to mixing part of the 12-HOA molecules in the Lα bilayers. Despite this mutual influence the structures of both the Lα phase and the gel network are hardly disturbed in the gelled Lα phase, i.e., that the self-assembly of the surfactant and of the gelator molecules clearly occur in an orthogonal way.

One-step formulation of nonionic surfactant bicelles (NSBs) by a double-tailed polyglycerol-type nonionic surfactant.

Bicelles are generally formed by phospholipid-based systems and are useful for various applications, such as nanocarriers or membrane protein crystallization. The same disc-like assemblies, nonionic surfactant bicelles (NSBs), can also be formed using nonionic amphiphiles, but this has not been reported extensively. We report a novel NSB system that employs the double-tailed nonionic amphiphile, polyglyceryl dialkyl ether (C12CmGn), which has two alkyl chains and a polyglyceryl group. A symmetric-tail molecule, C12C12G13.8, formed vesicles, whereas an asymmetric-tail molecule, C12C14G15.5, formed NSBs through a simple one-step process using ultrasonication. The 1 wt% aqueous solution of C12C14G15.5 was in a two-phase equilibrium of a lamellar phase and a water phase. Transparent dispersion was obtained through ultrasonication treatment. The size distribution in the dispersion was obtained by dynamic light scattering (DLS), resulting in a narrow distribution of around 20 nm in diameter. A negatively-stained transmission electron microscopy (TEM) image showed oblong and spherical shapes, which are typically observed in bicelle-forming systems. A small angle neutron scattering (SANS) measurement well proved bicelle formation by fitting a core-shell bicelle form factor model. The disc thickness and diameter were in agreement with the values obtained by DLS and TEM, respectively. A larger shell thickness at the rim part than at the flat disc part suggested that NSB aggregates have inhomogeneous molecular distribution. Similar to phospholipid systems, the bicelle-forming C12C14G15.5 system produced a defective lamellar phase formation at high surfactant concentrations, whereas a general lamellar phase was formed in the vesicle-forming C12C12G13.8 system.

Effects of Temperature and Humidity History on Brittleness of α-Sulfonated Fatty Acid Methyl Ester Salt Crystals.

α-Sulfonated fatty acid methyl ester salts (MES), which were made from vegetable sources, are attractive candidates for eco-friendly washing detergents because they have various special features like excellent detergency, favorable biodegradability, and high stability against enzymes. To overcome some disadvantages of powder-type detergents like caking, sorting, and dusting, we studied how temperature and humidity history, as a model for long-term storage conditions, can affect crystalline structures and reduce the brittleness of MES powder. We characterized the crystalline structure of MES grains using small-angle X-ray scattering, wide-angle X-ray scattering, differential scanning calorimetry, and Fourier transform infrared spectroscopy measurements and determined the yield values, which measure the brittleness of MES grains, in shear stress using dynamic viscoelasticity measurements. This study confirmed that MES crystals form three pseudo-polymorphs via thermal or humidity conditioning: metastable crystals (αsubcell), anhydrous crystals (ß subcell), and dihydrate crystals (ß' subcell). Further, we found that the yield value increases upon phase transition from the ß subcell to the ß' subcell and from the ß' subcell to the αsubcell. Therefore, controlling the thermal and humidity conditioning of MES grains is an effective way to decrease the brittleness of MES powders and can be used to overcome the above mentioned disadvantages of powder-type detergents in the absence of co-surfactants.

Formation of bilayer membrane and niosomes by double-tailed polyglyceryl-type nonionic surfactant.

Vesicles with synthetic nonionic surfactants are called niosomes or NSVs, and these have been the focus of attention as an alternative to phospholipid liposomes as drug carriers. Especially it is demanded to discover novel niosomal systems with polyol-type nonionic surfactants from the viewpoint of environmental aspects. In this paper, a novel series of double-tailed nonionic surfactants, polyglyceryl dialkyl ethers, (C12)2Gn (n = 2.3, 5.4, 9.4, and 13.8), was synthesized, and its aqueous phase behavior and niosome formation were studied. Because of its double-tailed molecular structure, a lamellar liquid crystalline phase was dominant in the binary phase diagrams for different polyglyceryl chain lengths. The single lamellar liquid crystalline phase region was expanded as the polymerization degree in the hydrophilic moiety increased. Small-angle X-ray scattering spectra revealed the lamellar structure for the (C12)2G2.3 was extremely loose. Molecular packing in the lamellar phase was analyzed except for the (C12)2G2.3 system by using a geometrical model of the lamellar phase. The effective cross-sectional area per molecule at the interface increased extensively as dilution for the (C12)2G13.8 system but remained almost unchanged for the (C12)2G5.4 system. From the molecular parameters, water-holding ability in the lamellar phase was evaluated, and the results indicated strong hydration ability of the long polyglyceryl chain. In a dilute region, micron-sized giant niosomes and small niosomes of about 100 nm were formulated by vortex mixing and ultrasonication, respectively. The multilamellar structure of the small niosomes was confirmed by transmission electron microscopy. Cholesterol addition in the present surfactant lamellar phase induced the phase transition to the liquid ordered phase, which is the same phenomenon in a phospholipid-cholesterol mixture. The stability of niosomes with/without cholesterol was monitored by the niosome size change. In both cases, the niosomes were stable for at least 100 days.

Preparation of O/I1-type Emulsions and S/I1-type Dispersions Encapsulating UV-Absorbing Agents.

Oil-in-cubic phase (O/I1) emulsions encapsulating the cosmetic UV absorbing agents 2-ethylhexyl 4-methoxycinnamate (EHMC), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (octocrylene, OCR) and 1-(4-tertbutylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione (Avobenzone, TBMP) were prepared by vortex mixing accompanied by a heating-cooling process. A ternary phase diagram in a water/C12EO25/EHMC system at 25°C was constructed and the two-phase equilibrium of an oil phase and an I1 phase, which is necessary to prepare the O/I1-type emulsions, was confirmed. Also, the melting of the I1 phase into a fluid micellar solution phase was confirmed, allowing emulsification by a heating-cooling process. The O/I1-type emulsions were formulated in the ternary system as well as a quaternary system. The four-component system contained an additional cosolvent, isopropyl myristate (IPM). The use of the cosolvent allows the use of reduced amounts of EHMC, which is desirable because EHMC can cause temporary skin irritation. Formulation of the O/I1-type emulsions with other UV absorbing agents (OCR and TBMP) was also possible using the same emulsification method. When IPM was changed to tripalmitin, which has a melting point greater than room temperature, a solid-oil dispersion in I1 phase was formed. We have termed this a "solidin-cubic phase (S/I1) type dispersion". These novel emulsions have not been reported previously. The UV absorbability of the O/I1-type emulsions and S/I1-type dispersions that encapsulate the UV absorbing agents was confirmed by measurement of UV absorption spectra.

Nonionic amphiphile nanoarchitectonics: self-assembly into micelles and lyotropic liquid crystals.

Amphiphiles, molecules that possess both hydrophilic and hydrophobic moieties, are architecturally simple molecules that can spontaneously self-assemble into complex hierarchical structures from lower to higher dimensions either in the bulk phase or at an interface. Recent developments in multifunctional nanostructure design using the advanced concept of nanoarchitectonics utilize this simple process of assembly. Amphiphilic self-assemblies involving lipids or proteins mimic the structure of biological systems, thus highlighting the necessity of a fundamental physical understanding of amphiphilic self-assembly towards a realization of the complex mechanisms operating in nature. Herein, we describe self-assembled microstructures of biocompatible and biodegradable tetraglycerol lauryl ether (C12G4) nonionic surfactant in an aqueous solvent system. Temperature-composition analyses of equilibrium phases identified by using small-angle x-ray scattering (SAXS) provide strong evidence of various spontaneously self-assembled mesostructures, such as normal micelles (Wm), hexagonal liquid crystal (H1), and reverse micelles (Om). In contrast to conventional poly(oxyethylene) nonionic surfactants, C12G4 did not exhibit the clouding phenomenon at higher temperatures (phase separation was not observed up to 100 °C), demonstrating the greater thermal stability of the self-assembled mesophases. Generalized indirect Fourier transformation (GIFT) evaluation of the SAXS data confirmed the formation of core-shell-type spherical micelles with a maximum dimension ca. 8.7 nm. The shape and size of the C12G4 micelles remained apparently unchanged over a wide range of concentrations (up to 20%), but intermicellar interactions increased and could be described by the Percus-Yevick (PY) theory (after Carnahan and Starling), which provides a very accurate analytical expression for the osmotic pressure of a monodisperse hard sphere.

Study on the formation of liquid ordered phase in lysophospholipid/cholesterol/1,3-butanediol/ water and lysophospholipid/ceramide/1,3- butanediol/water systems.

Formation of a liquid ordered phase in lysophospholipid/cholesterol/1,3-butanediol/water and lysophospholipid/ceramide/1,3-butanediol/water systems was investigated. Differential scanning calorimetry confirmed that a liquid ordered phase was formed in the lysophospholipid/cholesterol/1,3-butanediol/water system similar to that in phospholipid systems. The structure of liquid ordered phase was analyzed by using X-ray scattering measurements. It was revealed that the liquid ordered phase has a lamellar structure in which the hydrophobic chains are less ordered than in α-type crystals. On the other hand, in the lysophospholipid/ceramide/1,3-butanediol/water system, a liquid ordered phase was not formed.

Liquid crystal-based emulsions: progress and prospects.

Recent progress in lyotropic liquid crystal (LC)-based emulsions over the last few years has been reviewed. The tuning parameters for the formation, stability, rheology and transparency of LC-based emulsions are addressed. Recent applications of LC-based emulsions to the fabrication of dual meso/macroporous materials are also included.

Formation and cleansing performance of bicontinuous microemulsions in water/poly (oxyethylene) alkyl ether/ester-type oil systems.

Phase behaviors in water/poly(oxyethylene) dodecyl ether (C12EO(n), n = 4, 6, 8)/cetyl isooctanoate (CIO) systems were studied. In the C12EO6 and C12EO8 systems, self-assembled structures with positive curvatures, such as O/W microemulsions, and micellar cubic and hexagonal phases, were observed. A wider region of a lamellar liquid-crystalline phase, which included a narrow microemulsion region joined by a miscibility gap, was observed in the C12EO4 system. The structure of the microemulsion phase in the C12EO4 system was characterized by pulsed-field-gradient NMR (PFG-NMR) and small angle X-ray scattering (SAXS) techniques. PFG-NMR measurements indicated that the structure of the microemulsion was bicontinuous; both water and oil phases were continuous within the microemulsion. Pair-distance distribution function, p (r), and structure factors obtained by Generalized Indirect Fourier Transformation (GIFT) analysis of the SAXS data showed that the microemulsion domain sizes decreased with an increase in the oil content. The structure of the bicontinuous microemulsion was consistent with the results of a detergency test, in which the microemulsion samples were applied to lipstick dirt on an artificial skin plate. Detergency was observed to be better for the microemulsion at lower oil contents because of the larger oil domain size at these low concentrations.