All-Perfluorosulfonated-Ionomer Composite Membranes Containing Blow-Spun Fibers: Effect of a Thin Fiber Framework on Proton Conductivity and Mechanical Properties

In this study, thin fiber composite polymer electrolyte membranes (PEMs) were prepared using short side-chain perfluorosulfonic acid (PFSA) ionomers, Aquivion, to create composite PEMs with improved proton conductivity and improved mechanical properties. PFSA thin fiber webs prepared by blow spinning and successive hot pressing were used as the porous substrate. Herein, PFSA ionomers were used for both the substrate and the matrix of the composite PEMs, and their structures, properties, and fuel cell performance were characterized. By adding the PFSA thin fiber webs to the matrix, the proton conductivity was enhanced and the mechanical properties were slightly improved. The prepared PFSA thin fiber composite PEM showed better FC performance than that of the pristine PFSA one for the high-temperature low-humidity condition in addition to the low-temperature high-humidity one. To the best of our knowledge, this is the first report on the all PFSA composite membranes containing a PFSA thin fiber framework.

Structures of Nanoconfined Liquids Determined by Synchrotron X-ray Diffraction

We have successfully performed X-ray diffraction measurements of the liquids octamethylcyclotetrasiloxane (OMCTS, a quasi-spherical-shaped molecule) and n-hexadecane (a normal alkane) confined between mica surfaces at surface separation distances (D's) from 500 nm to the hard-wall thickness (1.9 nm for OMCTS and 1.0 nm for hexadecane). At all of the studied D's, we observed diffraction peaks corresponding to their mean intermolecular spacing at q = 8.6 nm^-1 (d = 0.73 nm) for OMCTS and q = 13.6 nm^-1 (d = 0.45 nm) for n-hexadecane. The peak intensity increased at D < ca. 50 nm for OMCTS even with the decreasing distance and exhibited a local maximum at D = 17-13 nm, indicating the sharp increase in the molecular order in this distance range. The peak intensities normalized by the D and I_normalized values of OMCTS and n-hexadecane were nearly constant at D's greater than 100 nm, though they appeared to increase slightly. The increase then became more significant with decreasing D below 100 nm, and finally the I_normalized values became 120 (for OMCTS) and 160 (for n-hexadecane) at the hard wall. These results clearly demonstrated the significant increase in the structural order of OMCTS and n-hexadecane under nanoconfinement, especially below 100 nm. The fwhm values of the peaks of OMCTS and n-hexadecane showed no significant change until small distances when the confinement effect was significant. These results indicated that the increase in the structural order should be mainly ascribed to the ordering of the molecules in the parallel plane in the enhanced layered structure formed under the confinement. The viscous parameters (b₂) of OMCTS and n-hexadecane obtained from the resonance shear measurement showed no increase at D's down to ca. 7 nm. This indicated that a certain ordering of the confined molecules was required for the observable increase in the viscosity.

Analysis of the sol and gel structures of potato starch over a wide spatial scale

We analyzed edible potato starch and observed the interaction between its granular structure and water molecules. We studied the changes caused by gelatinization during heating and stirring using microscopy, micro-FT-IR spectroscopy, and X-ray scattering techniques. A wide range of spatial scales was revealed using these various techniques. The rate of gelatinization varied significantly and was dependent on the starch concentration. The process of adsorption of water on starch molecules was studied using the humidity-controlled FT-IR spectroscopy technique. Furthermore, by comparing the X-ray scattering profiles of dry and wet granules, the 9-nm repeat "cluster" structure was studied. A gradual collapse of the granules occurred during the processes of heating and stirring. A clustered smectic structure and a smectic-like structure were observed in the opaque gel after gelatinization. Upon further heating, a transparent gel was obtained after the melting of the cluster.

Stratum Corneum Function: A Structural Study with Dynamic Synchrotron X-ray Diffraction Experiments

Studies on the effectiveness of substances such as drugs and cosmetics that act on the skin require structural evidence at the molecular level in the stratum corneum to clarify their interaction with intercellular lipid and soft keratin. For this purpose, when applying the substances to the stratum corneum X-ray diffraction experiment is one of the powerful tools. To detect minute structural changes in a stratum corneum sample, using a "solution cell", dynamic synchrotron X-ray diffraction measurements were performed when applying aqueous solution of the substances to the stratum corneum: (1) It was found that a surfactant, sodium dodecyl sulfate, significantly disrupted the long-period lamellar structure. (2) To study the effects of water, structural modifications of the short-period lamellar structure and the soft keratin in corneocytes were measured as a function of time. At the initial water content of 15 wt%, the spacings of the short-period lamellar structure and the soft keratin increased toward those at the water content of 25 wt%, that is a key water content in the stratum corneum. (3) Nanoparticles composed of assembly of amphiphilic molecules are one of the leading pharmaceutical formulations. When the nanoparticles were applied, a new assembly of amphiphilic molecules originated from the nanoparticle appeared. This phenomenon suggests that the formation of the new assembly at the surface of skin is concerned with the release of the drug from the nanoparticles. (4) When ethanol was applied to the stratum corneum, only the liquid state in the intercellular lipid matrix was dissolved. After the removal of ethanol from this stratum corneum, the ordered hydrocarbon-chain packing structures appeared. From this fact we would propose that the liquid state region is the main pathway for hydrophobic drugs with a small molecular weight in connection with the so-called 500 Da rule. Here, not only the technique but also the background to these studies and the characteristic results obtained from these studies are explained.

Impact of the Composition of Alcohol/Water Dispersion on the Proton Transport and Morphology of Cast Perfluorinated Sulfonic Acid Ionomer Thin Films

The dispersion of perfluorinated sulfonic acid ionomers in catalyst inks is an important factor that controls the performance of catalyst layers in membrane electrode assemblies of polymer electrolyte fuel cells. Herein, the effects of water/alcohol compositions on the morphological properties and proton transport are examined by grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and electrochemical impedance spectroscopy. The thin films cast by a high water/alcohol ratio Nafion dispersion have high proton conductivity and well-defined hydrophilic/hydrophobic phase separation, which indicates that the proton conductivity and morphology of the Nafion thin films are strongly influenced by the state of dispersion. This finding is expected to further understand the morphology and proton transport properties of Nafion thin films with different water/alcohol ratios, which has implications for the performance of the Pt/Nafion interface.

Preparation of Perfluorosulfonated Ionomer Nanofibers by Solution Blow Spinning

In this work, we report the preparation of high-purity perfluorosulfonated ionomer (Nafion) nanofibers (NFs) via solution blow spinning (SBS). Fiber formation in solution jet spinning is strongly dependent on the structure of the spinning solution. Upon adding a small amount of poly(ethyleneoxide) (PEO) as a spinning aid to Nafion dispersion, most of the highly ordered Nafion aggregate disappeared, allowing the stable production of bead-free and smooth high-purity NFs (Nafion/PEO = 99/1) by SBS. The microstructure of the blowspun Nafion NFs differed from that of electrospun NFs. In the blowspun NFs, incomplete microphase separation between hydrophilic (ionic) and hydrophobic domains was observed, but the crystallization of CF2-CF2 chains was enhanced owing to the high extensional strain rate and rapid solidification during SBS. These findings provide fundamental information for the preparation and characterization of blowspun Nafion NFs.

Chiral Silica with Preferred-Handed Helical Structure via Chiral Transfer

A strategy to obtain chiral silica using an achiral stereoregular polymer with polyhedral oligomeric silsesquioxane (POSS) side chains is described herein. The preferred helical conformation of the POSS-containing polymer could be achieved by mixing isotactic polymethacrylate-functionalized POSS (it-PMAPOSS) and a chiral dopant. The array structure of POSS molecules, which are placed along the helical conformation, is memorized even after removing the chiral dopant at high temperatures, leading to a chiral silica compound with exclusive optical activity after calcination.

Effects of surface and shear forces on nano-confined smectic-A liquid crystals studied by X-ray diffraction

The orientational behavior of a smectic-A liquid crystal (4-cyano-4'-octylbiphenyl, 8CB) confined between mica surfaces as well as between silica surfaces with a nanometer scale thickness was investigated by synchrotron X-ray diffraction measurement. The crystallographic axes of two confining mica sheets were adjusted parallel to each other to induce the preferential orientation of 8CB molecules along their crystallographic axis. The silica surfaces, which were hydrophilic and amorphous and had nanometer level smoothness, were prepared on mica surfaces using a sputtering technique. The X-ray diffraction measurement revealed that the 8CB molecules, confined between mica surfaces (DHW = 1.7 nm) and between silica surfaces (DHW = ca. 2 nm), took a planar orientation (oriented its long axis parallel to the surface) and formed a lamellar structure. However, the in-plane orientation of the confined 8CB changed depending on the confining surfaces. The lamellar axis of the 8CB confined between mica surfaces uniaxially oriented most probably due to the preferential alignment of its long axis along the principal crystallographic a-axis of the mica. On the other hand, 8CB between the silica surfaces formed lamellar domains in which the lamellar axis of 8CB omnidirectionally oriented in-plane. The effect of the shear on the orientation of the nano-confined 8CB was also investigated. The lamellar axis, corresponding to the long axis of the 8CB molecules confined between the mica surfaces, rotated only ca. 3 degrees within the plane parallel to the surface by perpendicularly applying shear to the axis. The lamellar axis of the 8CB molecules between the silica surfaces showed no noticeable change by applying the shear. These results indicated that the effect of shear to align the 8CB molecules was significantly suppressed due to the confinement effect which significantly reduces the mobility of molecules as well as the alignment effect along the crystallographic axis in the case of mica. We also observed a change in the orientation of nano-confined 8CB after shear treatment at large D (= 3.3 μm).

Polar-Nonpolar Interfaces of Normal Bicontinuous Cubic Phases in Nonionic Surfactant/Water Systems Are Parallel to the Gyroid Surface

We investigated the structures of normal (type I) bicontinuous cubic phases in hexa-, hepta-, and octaethylene glycol dodecyl ether/water mixtures by small-angle X-ray crystallography of single-crystal domains. Reconstructed electron densities showed that the hydrophilic chains with high electron density are confined to a film centered on the surface of the Gyroid (a triply periodic minimal surface), while hydrophobic chains with low electron density are distributed within the pair of interwoven labyrinths carved out by the Gyroid. Further, the local minimum within the high electron density region, due to bulk water, coincides precisely with the Gyroid. This minimum is less pronounced in mixtures with longer ethylene glycol chains, consistent with their decreased water content. Our analysis clearly shows that the polar-nonpolar interfaces are parallel to the Gyroid surface in all mixtures. The repulsive hydration or overlapping force between the pair of facing monolayers of ethylene glycol chains on either side of the Gyroid surface is the likely origin of the parallel interfaces.

Microbeam X-ray diffraction study of lipid structure in stratum corneum of human skin

Human skin, not previously frozen, was studied by small-angle X-ray diffraction. The samples were folded so that a 6μm X-ray beam passed through the top layer of skin, stratum corneum. Diffraction patterns recorded with this method consisted of peaks at about q = 0.5, 1.0 and 1.4 nm-1 in the direction perpendicular to the skin surface more clearly than in previous studies. These peaks are interpreted to arise from lipids between corneocytes. A simple unit of a linear electron density profile with three minima was used to account for the observed intensity profiles. Combinations of calculated diffraction from models with one, two and three units accounted for the major part of the observed diffraction pattern, showing the diversity in the structure of the intercellular lipids.

Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions

The morphological changes of Nafion thin films with thicknesses from 10 to 200 nm on Pt substrate with various annealing histories (unannealed to 240 °C) were systematically investigated using grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS). The results revealed that the hydrophilic ionic domain and hydrophobic backbone in Nafion thin films changed significantly when the annealing treatment exceeded the cluster transition temperature, which decreased proton conductivity, due to the constrained hydrophilic/hydrophobic phase separation, and increased the crystalline-rich domain. This research contributed to the understanding of ionomer thermal stability in the catalyst layer, which is subjected to thermal annealing during the hot-pressing process.

Mechanical Stabilization of Deoxyribonucleic Acid Solid Films Based on Hydrated Ionic Liquid

Solid films of deoxyribonucleic acid (DNA) containing a hydrated ionic liquid, choline dihydrogen phosphate (CDP), were prepared by a solvent-casting method. Thermal properties, aggregation structure, thermal molecular motion, and tensile properties of CDP-containing DNA films were examined by thermogravimetry (TG), wide-angle X-ray diffraction (WAXD) measurement, dynamic mechanical analysis (DMA), and tensile tests, respectively. The water retentivity of the films at room temperature was much improved with CDP. The packing density of DNA helical chains clearly depended on the amount of CDP in the film. A small amount of CDP contributed to the suppression of the B_I → B_II conformational transition and the cooperative motion of the DNA duplex in the film. The tensile properties of the film drastically changed in the presence of CDP. When the amount of hydrated CDP in the film increased, the mechanical response of the film changed from glassy-like to rubbery-like via a semicrystalline-like state. The above results make it clear that CDP plays two major roles as a water absorber and plasticizer in the DNA film. Thus, it can be concluded that the use of an ionic liquid as an additive significantly increases the possibility of using a DNA solid film as a structural material.

Unraveling the kinetics of the structural development during polymerization-induced self-assembly: decoupling the polymerization and the micelle structure

Upon extending a hydrophobic polymer chain from the end of a preceding hydrophilic chain in aqueous solutions, the resultant block copolymers may eventually undergo self-assembly.

Fluorination and chlorination effects on quinoxalineimides as an electron-deficient building block for n-channel organic semiconductors

The quinoxalineimide (QI) unit, containing the electron-withdrawing quinoxaline and imide groups, is an electron-deficient building block for organic semiconductor materials. In this study, three fluorinated or chlorinated QIs (QI-1F, QI-2F, and QI-2Cl), have been designed and developed. We report the impact of the fluorination or chlorination of the QI unit on the electronic structures and charge carrier transport properties as compared to unsubstituted QI (QI-2H) bearing the same n-hexyl side chains. The frontier molecular orbital energy levels downshifted with the incorporation of fluorine or chlorine atoms onto the π-framework of QI. Single-crystal structure analyses revealed that all QI-based molecules have an entirely planar backbone and are packed into two-dimensional slipped stacks with diagonal electronic coupling that enables two-dimensional charge carrier transport. Notably, the doubly fluorinated or chlorinated QIs formed compact molecular packing in the single-crystal structures through an infinite intermolecular network relative to unsubstituted QI (QI-2H). The field-effect transistor-based QI molecules exhibited typical n-channel transport properties. As compared to unsubstituted QI (QI-2H), the chlorinated QI exhibited improved electron mobilities up to 7.1 × 10⁻³ cm² V⁻¹ s⁻¹. The threshold voltages of the fluorinated or chlorinated QI devices were clearly smaller than that of QI-2H, which reflects the lowest unoccupied molecular orbital levels of the molecules. This study demonstrates that the fluorinated or chlorinated QIs are versatile building blocks in creating n-channel organic semiconductor materials.

Three fluorinated or chlorinated quinoxalineimide units (QI-1F, QI-2F, and QI-2Cl) have been designed and developed.

Polar-Nonpolar Interfaces of Inverse Bicontinuous Cubic Phases in Phytantriol/Water System are Parallel to Triply Periodic Minimal Surfaces

We investigated two distinct lyotropic liquid crystal inverse bicontinuous cubic phases of phytantriol/water mixtures by small-angle X-ray crystallography of the single-crystal regions. Reconstructed electron density maps revealed hydrophilic head and hydrophobic tail regions of the phytantriol bilayer membranes and water regions. The bilayer membranes are shown to be located on the D and gyroid triply periodic minimal surfaces. To investigate the structures of the polar-nonpolar interfaces, we optimized two models: a parallel surface model and a constant mean curvature surface model. The parallel surface model agreed well with the X-ray data, and the R factors, which show the degree of agreement between those structural models and the data, were less than 0.04. In stark contrast, the constant mean curvature surface model deviated significantly from the data, and the R factors were around 0.15. We therefore conclude that the polar-nonpolar interface of the inverse bicontinuous cubic phase of the phytantriol/water system is close to a parallel surface to a triply periodic minimal surface.

Diffracted X-ray Blinking Tracks Single Protein Motions

Single molecule dynamics studies have begun to use quantum probes. Single particle analysis using cryo-transmission electron microscopy has dramatically improved the resolution when studying protein structures and is shifting towards molecular motion observations. X-ray free-electron lasers are also being explored as routes for determining single molecule structures of biological entities. Here, we propose a new X-ray single molecule technology that allows observation of molecular internal motion over long time scales, ranging from milliseconds up to 10³ seconds. Our method uses both low-dose monochromatic X-rays and nanocrystal labelling technology. During monochromatic X-ray diffraction experiments, the intensity of X-ray diffraction from moving single nanocrystals appears to blink because of Brownian motion in aqueous solutions. X-ray diffraction spots from moving nanocrystals were observed to cycle in and out of the Bragg condition. Consequently, the internal motions of a protein molecule labelled with nanocrystals could be extracted from the time trajectory using this diffracted X-ray blinking (DXB) approach. Finally, we succeeded in distinguishing the degree of fluctuation motions of an individual acetylcholine-binding protein (AChBP) interacting with acetylcholine (ACh) using a laboratory X-ray source.

Depth-Resolved Characterization of Perylenediimide Side-Chain Polymer Thin Film Structure Using Grazing-Incidence Wide-Angle X-ray Diffraction with Tender X-rays

Polymers with a perylenediimide (PDI) side chain (PAc12PDI) consist of two kinds of crystalline structures with various types of orientations in a thin film. Understanding the population of the microcrystalline structure and its orientation along the thickness is strongly desired. Grazing-incidence wide-angle X-ray diffraction (GIWAXD) measurements with hard X-rays, which are generally chosen as λ = 0.1 nm, are a powerful tool to evaluate the molecular aggregation structure in thin films. A depth-resolved analysis for the outermost surface of the polymeric materials using conventional GIWAXD measurements, however, has limitations on depth resolution because the X-ray penetration depth dramatically increases above the critical angle. Meanwhile, tender X-rays (λ = 0.5 nm) have the potential advantage that the penetration depth gradually increases above the critical angle, leading to precise characterization for the population of crystallite distribution along the thickness. The population of the microcrystalline states in the PAc12PDI thin film was precisely characterized utilizing GIWAXD measurements using tender X-rays. The outermost surface of the PAc12PDI thin film is occupied by a monoclinic lattice with a = 2.38 nm, b = 0.74 nm, c = 5.98 nm, and β = 108.13°, while maintaining the c-axis perpendicular to the substrate surface. Additionally, the presence of solid substrate controls the formation of the crystallite with unidirectional orientation.

Preparation of High-Density Polymer Brushes with a Multihelical Structure

It is well-known that a mixture of isotactic and syndiotactic polymethyl methacrylate (PMMA) forms a stereocomplex consisting of a multihelical structure in which an isotactic chain is surrounded by a syndiotactic chain. Here, we report the basic structure of the stereocomplex formed when the syndiotactic PMMA chains are tethered to a silicon substrate and form a high-density polymer brush. The influence of geometric confinement was investigated by preparing the high-density polymer brushes on a flat and spherical substrate. In both cases, mixing the untethered isotactic PMMA with the grafted syndiotactic PMMA led to the formation of a stereocomplex with a multihelical structure. Static contact angle measurements showed a hindered surface mobility at the outermost surface of the polymer brush, indicating that the stereocomplex forms a crystalline structure. A syndiotactic polymer brush with substituted fluoroalkyl groups was prepared to increase the contrast for grazing incidence wide-angle X-ray diffraction (GIWAXD) measurements. The GIWAXD results verified that the stereocomplex forms a crystalline structure oriented perpendicular to the substrate with a relatively low degree of orientation.

Design of High-Density Helical Polymer Brush on Silica Nanoparticles for the Size Recognition of Fullerene Molecules

High-density syndiotactic poly(methyl methacrylate) (st-PMMA) brushes form a helical structure and encapsulate fullerene molecules in their helical cavities, leading to a PMMA brush/fullerene inclusion complex. The brushes recognize the size of guest molecules and spontaneously adapt their helical diameter to the guest molecules. Both polymer brush/C₆₀ and polymer brush/C₇₀ inclusion complex on the flat substrate were characterized on the basis of grazing incidence wide-angle X-ray diffraction (GIWAXD) measurements, and it is revealed that the main chains oriented perpendicular to the substrate. Moreover, high-density st-PMMA brushes grafted onto nanoparticles efficiently separate C₇₀ molecules from the mixture of C₆₀ and C₇₀ solution. Even after 5× repeating process, the selectivity for C₇₀ molecules remains at 99%.

X-Ray diffraction and resonance shear measurement of nano-confined ionic liquids

The X-ray diffraction and resonance shear measurement (RSM) demonstrated the relation between the structure and lubrication properties of ionic liquid ([C₄mim][NTf₂], [C₄mim][BF₄]) films of nanometer thickness confined between silica surfaces.

Transformation of Coiled α-Helices into Cross-β-Sheets Superstructure

The fibrous silk produced by bees, wasps, ants, or hornets is known to form a four-strand α-helical coiled coil superstructure. We have succeeded in showing the formation of this coiled coil structure not only in natural fibers, but also in artificial films made of regenerated silk of the hornet Vespa simillima xanthoptera using wide- and small-angle X-ray scatterings and polarized Fourier transform infrared spectroscopy. On the basis of time-resolved simultaneous synchrotron X-ray scattering observations for in situ monitoring of the structural changes in regenerated silk material during tensile deformation, we have shown that the application of tensile force under appropriate conditions induces a transition from the coiled α-helices to a cross-β-sheet superstructure. The four-stranded tertiary superstructure remains unchanged during this process. It has also been shown that the amorphous protein chains in the regenerated silk material are transformed into conventional β-sheet arrangements with varying orientation.

Molecular Interaction between Intercellular Lipids in the Stratum Corneum and l-Menthol, as Analyzed by Synchrotron X-Ray Diffraction

l-Menthol increases drug partitioning on the surface of skin, diffusion of drugs in the skin, and lipid fluidity in the stratum corneum and alters the rigidly arranged lipid structure of intercellular lipids. However, l-menthol is a solid at room temperature, and it is difficult to determine the effects of l-menthol alone. In this study, we vaporized l-menthol in order to avoid the effects of solvents. The vaporized l-menthol was applied to the stratum corneum or lipid models comprising composed of ceramides (CER) [EOS], the longest lipid acyl chain of the ceramides in the stratum corneum lipids that is associated with the barrier function of the skin; CER [NS], the shorter lipid acyl chain of the ceramides, and the most components in the stratum corneum of the intercellular lipids that is associated with water retention in the intercellular lipid structure of the stratum corneum; cholesterol; and palmitic acid. Synchrotron X-ray diffraction, differential scanning calorimetry, and attenuated total reflection Fourier transform infrared spectroscopy analyses revealed that the lipid models were composed of hexagonal packing and orthorhombic packing structures of different lamellar periods. Taken together, our results revealed that l-menthol strongly affected the lipid model composed of CER [EOS]. Therefore, l-menthol facilitated the permeation of drugs through the skin by liquid crystallization of the longer lamellar structure. Importantly, these simple lipid models are useful for investigating microstructure of the intercellular lipids in the stratum corneum.

Platonic Micelles: Monodisperse Micelles with Discrete Aggregation Numbers Corresponding to Regular Polyhedra

The concept of micelles was first proposed in 1913 by McBain and has rationalized numerous experimental results of the self-aggregation of surfactants. It is generally agreed that the aggregation number (N_agg) for spherical micelles has no exact value and a certain distribution. However, our studies of calix[4]arene surfactants showed that they were monodisperse with a defined N_agg whose values are chosen from 6, 8, 12, 20, and 32. Interestingly, some of these numbers coincide with the face numbers of Platonic solids, thus we named them “Platonic micelles”. The preferred N_agg values were explained in relation to the mathematical Tammes problem: how to obtain the best coverage of a sphere surface with multiple identical circles. The coverage ratio D(N) can be calculated and produces maxima at N = 6, 12, 20, and 32, coinciding with the observed N_agg values. We presume that this “Platonic nature” may hold for any spherical micelles when N_agg is sufficiently small.

Elastomers built up through the π–π stacking association of polycyclic planar aromatic diimides

Polymers composed of polycyclic aromatic planar diimide (PCAD) units and flexible rubbery poly(propylene glycol) (PPG) chains were synthesized, and the morphology and viscoelasticity were investigated.

Effect of Nerolidol and/or Levulinic Acid on the Thermotropic Behavior of Lipid Lamellar Structures in the Stratum Corneum

Permeation enhancers are required to deliver drugs through the skin efficiently and maintain effective blood concentrations. Studies of the barrier function of the stratum corneum using l-menthol, a monocyclic monoterpene widely used in medicines and foods, have revealed an interaction between characteristic intercellular lipid structures in the stratum corneum and permeation enhancers. The variety of permeation enhancers that can be used to contribute to transdermal delivery systems beyond l-menthol is increasing. In this study, we focused on nerolidol and levulinic acid and investigated their influence on stratum corneum lipid structures. Nerolidol, a sesquiterpene, has been reported to enhance the permeation of various drugs. Levulinic acid is reported to enhance the permeability of buprenorphine and is used as a component of the buprenorphine^® patch. Synchrotron X-ray diffraction and attenuated total reflectance Fourier transform IR spectroscopy measurements revealed that nerolidol disturbs the rigidly arranged lipid structure and increases lipid fluidity. Levulinic acid had a smaller effect on stratum corneum lipid structures, but did increase lipid fluidity when co-administered with nerolidol or heat. We found that nerolidol has an effect on stratum corneum lipids similar to that of l-menthol, and levulinic acid had an effect similar to that of oleic acid.

Identification of a Plasmid-Mediated Quinolone Resistance Gene in Salmonella Isolates from Texas Dairy Farm Environmental Samples

A recent increase in plasmid-mediated quinolone resistance (PMQR) has been detected among Salmonella isolated from humans in the United States, and it is necessary to determine the sources of human infection. We had previously isolated Salmonella from dairy farm environmental samples collected in Texas, and isolates were tested for anti-microbial susceptibility. Two isolates, serotyped as Salmonella Muenster, showed the discordant pattern of nalidixic acid susceptibility and intermediate susceptibility to ciprofloxacin. For this project, whole-genome sequencing of both isolates was performed to detect genes associated with quinolone resistance. The plasmid-mediated qnrB19 gene and IncR plasmid type were identified in both isolates. To our knowledge, this is the first report of PMQR in Salmonella isolated from food animals or agricultural environments in the United States.

Two Distinct Cylinder Arrangements in Monodomains of a Lyotropic Liquid Crystalline Hexagonal II Phase: Monodomains with Straight Cylinders and Ringed Cylinders in Capillaries

We report a method to produce two different monodomains of an inverse hexagonal II (HII) phase in capillaries. Capillaries filled with glyceryl monooleyl ether (GME) in an inverted micellar phase were soaked in water. After a week, a monodomain of the HII phase with straight cylinders was observed in a capillary with a diameter of 1.0 mm. The axis of the straight cylinders was almost parallel to the capillary axis, and the cylinders were slightly undulated. The lattice constant of the HII phase was 5.85 nm, which indicated the monodomain was fully hydrated. Another monodomain with ringed cylinders was observed in a 0.2 mm diameter capillary. The ringed cylinders aligned to the round capillary wall, where one of the ⟨10⟩ directions in the hexagonal lattice always faced the wall. The lattice constant was 4.89 nm, from which the estimated water content of the monodomain was almost the lowest reported for the HII phase. The monodomain with ringed cylinders is stabilized by the capillary wall and the low water content. This method to produce specific monodomains is expected to be of benefit for basic and applied research on the HII phase.

In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts

A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated by in situ ultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis of in situ USAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction in proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress-strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.

Molecular Orientation Enhancement of Silk by the Hot-Stretching-Induced Transition from α-Helix-HFIP Complex to β-Sheet

Enhancing the molecular orientation of the regenerated silk fibroin (RF) up to a level comparable to the native silk is highly challenging. Our novel and promising strategy for the poststretching process is (1) creating at first an α-helix-HFIP complex with a hexagonal packing as an intermediate state and then (2) stretching it at a high temperature to induce the helix-to-sheet structural phase transition. Here we show for the first time the significantly high stretching efficiency of the proposed technique compared with the conventional wet-stretching techniques and the successful achievement of higher crystalline orientation and higher Young's modulus compared even with the native silk. The detailed structural analysis based on the time-resolved simultaneous measurement of stress-strain curve, synchrotron X-ray scatterings, and FTIR has revealed the structural transition mechanism from the hexagonally packed α-helix-HFIP complex to the highly oriented β-sheet crystalline state as well as the critical level of crystal orientation needed for the helix-to-sheet transition.