Small-angle X-ray scattering analysis of poly(amic acid) dispersed in a liquid matrix to understand the size control of polyimide nanoparticles.

Poly(amic ‍acid) ‍nanoparticles ‍prepared ‍by ‍‍precipitation ‍polymerization with a dispersant were evaluated by small-angle X-ray scattering (SAXS) and field-emission scanning electron microscopy (FE-SEM). The particle size evaluation of poly(amic acid) nanoparticles in the liquid phase by SAXS was performed to gain insight into the size control of poly(amic acid) nanoparticles, and showed good agreement with visual observation by FE-SEM, explaining the effect of the dispersant in obtaining polyimide nanoparticles with small particle size. This indicates that the particle size is maintained without change during the solvent evaporation process.

Chiral Transfer of Linear Polysiloxane with Preferred-Handed Helical Conformation.

We report the preparation of chiral silica using a linear polysiloxane main chain with a preferred-handed helical structure as the template. Poly(methylvinyl siloxane) (PMVS) with a cysteine derivative side chain designated as PMVS-Cys was prepared using anionic polymerization and an ene-thiol reaction. PMVS-Cys forms a helical conformation in both solution and film via hydrogen bonding between amide groups at side chains.

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.

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 -hexadecane (a normal alkane) confined between mica surfaces at surface separation distances ('s) from 500 nm to the hard-wall thickness (1.9 nm for OMCTS and 1.0 nm for hexadecane).

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.

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 (-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.

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.

Microstructure Investigation of Polymer Electrolyte Fuel Cell Catalyst Layers Containing Perfluorosulfonated Ionomer.

Perfluorosulfonated ionomers are the most successful ion-exchange membranes at an industrial scale. One recent, cutting-edge application of perfluorosulfonated ionomers is in polymer electrolyte fuel cells (PEFCs). In PEFCs, the ionomers are used as a component of the catalyst layer (CL) in addition to functioning as a proton-exchange membrane.

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.

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.

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.

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.

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.

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.

Structure of Ultrafine Bubbles and Their Effects on Protein and Lipid Membrane Structures Studied by Small- and Wide-Angle X-ray Scattering.

Ultrafine bubbles (UFBs) are defined as small gas-filled bubbles with a diameter smaller than 1 μm. UFBs are stable for several weeks in aqueous solutions due to their small size. Although the mechanism of the stability of UFBs remains under intensive investigation, industrial applications of UFBs have recently arisen in various fields such as agricultural and fishery industries and medical therapy.

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.

Restoration of Myoglobin Native Fold from Its Initial State of Amyloid Formation by Trehalose.

Organisms having tolerances against extreme environments produce and accumulate stress proteins and/or sugars in cells against the extreme environment such as high or low temperature, drying, and so forth. Sugars and/or polyols are known to prevent protein denaturation and enzyme deactivation. In particular, trehalose has received considerable attention because of its association with cryptobiosis and anhydrobiosis.

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.

Preferential Intercalation of Human Amyloid-β Peptide into Interbilayer Region of Lipid-Raft Membrane in Macromolecular Crowding Environment.

This study focuses on the interaction of human amyloid β-peptide (Aβ) with a lipid-raft model membrane under macromolecular crowding conditions that mimic the intracellular environment. Aβ is central to the development of Alzheimer's disease (AD) and has been studied extensively to determine the molecular mechanisms of Aβ-induced cellular dysfunctions underlying the pathogenesis of AD. According to evidence from spectroscopic studies, ganglioside clusters are key to the fibrillization process of Aβ.

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.

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

X-ray diffraction measurement at the SPring-8 synchrotron was employed to investigate the structures of two types of imidazolium-based ionic liquids (ILs), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTF2]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), confined between silica surfaces by varying the surface separation distances of ca. 500 nm (bulk liquid), ca. 10 nm, and ca.

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

High-density syndiotactic poly(methyl methacrylate) (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/C and polymer brush/C 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.

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.