Time-resolved AUSAXS at BL28XU at SPring-8.

An anomalous ultra-small-angle X-ray scattering (AUSAXS) system has been constructed at BL28XU at SPring-8 for time-resolved AUSAXS experiments. The path length was extended to 9.1 m and a minimum of q = 0.0069 nm-1 was attained. Scattering profiles at 0.0069 to 0.3 nm-1 were successfully obtained at 17 different X-ray energies in 30 s using the BL28XU optical setup, which enables adjustment of the energy of the incident X-rays quickly without the beam position drifting. Time-resolved measurements were conducted to investigate changes in the structure of zinc compounds in poly(styrene-ran-butadiene) rubber during vulcanization. A change in energy dependence of the scattered intensity with time was found during vulcanization, suggesting the transformation of zinc in the reaction.

Pseudomorphic amorphization of three-dimensional superlattices through morphological transformation of nanocrystal building blocks.

Nanocrystal (NC) superlattices (SLs) have been widely studied as a new class of functional mesoscopic materials with collective physical properties. The arrangement of NCs in SLs governs the collective properties of SLs, and thus investigations of phenomena that can change the assembly of NC constituents are important. In this study, we investigated the dynamic evolution of NC arrangements in three-dimensional (3D) SLs, specifically the morphological transformation of NC constituents during the direct liquid-phase synthesis of 3D NC SLs. Electron microscopy and synchrotron-based in situ small angle X-ray scattering experiments revealed that the transformation of spherical Cu2S NCs in face-centred-cubic 3D NC SLs into anisotropic disk-shaped NCs collapsed the original ordered close-packed structure. The random crystallographic orientation of spherical Cu2S NCs in starting SLs also contributed to the complete disordering of the NC array via random-direction anisotropic growth of NCs. This work demonstrates that an understanding of the anisotropic growth kinetics of NCs in the post-synthesis modulation of NC SLs is important for tuning NC array structures.

Neutron reflectivity study on the nanostructure of PMMA chains near substrate interfaces based on contrast variation accompanied with small molecule sorption.

In the case of poly(methyl methacrylate) (PMMA) thin films on a Si substrate, thermal annealing induces the formation of a layer of PMMA chains tightly adsorbed near the substrate interface, and the strongly adsorbed PMMA remains on the substrate, even after washing with toluene (hereinafter called adsorbed sample). Neutron reflectometry revealed that the concerned structure consists of three layers: an inner layer (tightly bound on the substrate), a middle layer (bulk-like), and an outer layer (surface) in the adsorbed sample. When an adsorbed sample was exposed to toluene vapor, it became clear that, between the solid adsorption layer (which does not swell) and bulk-like swollen layer, there was a "buffer layer" that could sorb more toluene molecules than the bulk-like layer. This buffer layer was found not only in the adsorbed sample but also in the standard spin-cast PMMA thin films on the substrate. When the polymer chains were firmly adsorbed and immobilized on the Si substrate, the freedom of the possible structure right next to the tightly bound layer was reduced, which restricted the relaxation of the conformation of the polymer chain strongly. The "buffer layer" was manifested by the sorption of toluene with different scattering length density contrasts.

Neutron Reflectivity Study on the Suppression of Interfacial Water Accumulation between a Polypropylene Thin Film and Si Substrate Using a Silane-Coupling Agent.

We measured the neutron reflectivity (NR) of isotactic polypropylene (PP) thin films deposited on Si substrates modified by hexamethyldisilazane (HMDS) at the saturated vapor pressure of deuterated water at 25 °C and 60 °C/85% RH to investigate the effect of HMDS on the interfacial water accumulation in PP-based polymer/inorganic filler nanocomposites and metal/resin bonding materials. We found that the amount of water accumulated at the PP/Si interface decreased with increasing immersion time of the Si substrate in a solution of HMDS in hexane prior to PP film deposition. During the immersion of the Si substrate, the HMDS molecules were deposited on the Si substrate as a monolayer without aggregation. Furthermore, the coverage of the HMDS monolayer on the Si substrate increased with increasing immersion time. At 60 ° C and 85% RH, only a slight amount of interfacial water was detected after HMDS treatment for 1200 min. As a result, the maximum concentration of interfacial water was reduced to 0.1 from 0.3, where the latter corresponds to the PP film deposited on the untreated substrate.

Investigation of Interfacial Water Accumulation between Polypropylene Thin Film and Si Substrate by Neutron Reflectivity.

We performed neutron reflectivity (NR) measurements of isotactic polypropylene (PP) thin films deposited on a Si substrate at the saturated vapor pressure of deuterated water to investigate interfacial water accumulation between the PP and metal surfaces in PP-based polymer/inorganic filler nanocomposites and metal/resin bonding materials. The PP thin films prepared on a Si substrate by a spin-coating technique were adequate as a model system for the PP/metal interface in these materials. A water-rich layer with a maximum water concentration of 0.5, which was considerably higher than those reported in previous studies of organic/inorganic interfaces, was observed within a width of approximately 3 nm at the interface under saturated vapor conditions. This could be attributed to the weak interaction between the PP thin film and the Si substrate. The pathway of moisture transport to the interfacial region was along the interface rather than through the PP film because the hydrophobic PP thin film does not entirely swell with water vapor.

Unique arrangement of bone matrix orthogonal to osteoblast alignment controlled by Tspan11-mediated focal adhesion assembly.

During tissue construction, cells coordinate extracellular matrix (ECM) assembly depending on the cellular arrangement. The traditional understanding of the relationship between the ECM and cells is limited to the orientation-matched interaction between them. Indeed, it is commonly accepted that the bone matrix (collagen/apatite) is formed along osteoblast orientation. Nonetheless, our recent findings are contrary to the above theory; osteoblasts on nanogrooves organize formation of the bone matrix perpendicular to cell orientation. However, the precise molecular mechanisms underlying the orthogonal organization of bone matrix are still unknown. Here, we show that mature fibrillar focal adhesions (FAs) facilitate the perpendicular arrangement between cells and bone matrix. The osteoblasts aligned along nanogrooves expressed highly mature fibrillar FAs mediated by integrin clustering. Microarray analysis revealed that Tspan11, a member of the transmembrane tetraspanin protein family, was upregulated in cells on the nanogrooved surface compared with that in cells on isotropic, flat, or rough surfaces. Tspan11 silencing significantly disrupted osteoblast alignment and further construction of aligned bone matrix orthogonal to cell orientation. Our results demonstrate that the unique bone matrix formation orthogonal to cell alignment is facilitated by FA maturation. To the best of our knowledge, this report is the first to show that FA assembly mediated by Tspan11 determines the direction of bone matrix organization.

Control of Phase Separation in Polystyrene/Ionic Liquid-Blended Films by Polymer Brush-Grafted Particles.

Immiscible composite materials with controlled phase-separated structures are important in areas ranging from catalysis to battery. We succeeded in controlling the phase-separated structures of immiscible blends of polystyrene (PS) and two ionic liquids (ILs), namely, N, N-diethyl- N-(2-methoxyethyl)- N-methylammonium bis(trifluoromethylsulfonyl)imide (DEME-TFSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, by adding precisely designed concentrated polymer brush-grafted (CPB-grafted) silica nanoparticles (CPB-SiPs) prepared by surface-initiated atom-transfer radical polymerization. We discuss relationships between chemical species and molecular weights of the CPB and phase-separated structures. When the CPB was composed of a PS homopolymer of an appropriate molecular weight, the IL phase formed a continuous structure and a quasi-solid-blended film was successfully fabricated because the CPB-SiPs were adsorbed at the PS/IL interface and prevented macroscopic phase separation. We propose that CPB-SiP adsorption and the fabrication of quasi-solid films are governed by the degree of penetration of the matrix PS chains into the CPB and deformability of the CPB-SiPs. We found that the DEME-TFSI domain size can be controlled by the CPB-SiP content and that only 1 wt % of the CPB-SiPs was needed to fabricate a quasi-solid film. In addition, we investigated the ionic properties of the quasi-solid PS/DEME-TFSI-blended film. Owing to continuous ion channels composed only of DEME-TFSI, the film exhibited an ionic conductivity of 0.1 mS/cm, which is relatively high compared to previously reported quasi-solid electrolytes. Finally, we demonstrated that an electric double-layer capacitor fabricated using this film as the electrolyte exhibited high charge/discharge cycling stability and reversibility.

USAXS analysis of concentration-dependent self-assembling of polymer-brush-modified nanoparticles in ionic liquid: [I] concentrated-brush regime.

Using ultra-small angle X-ray scattering (USAXS), we analyzed the higher-order structures of nanoparticles with a concentrated brush of an ionic liquid (IL)-type polymer (concentrated-polymer-brush-modified silica particle; PSiP) in an IL and the structure of the swollen shell layer of PSiP. Homogeneous mixtures of PSiP and IL were successfully prepared by the solvent-casting method involving the slow evaporation of a volatile solvent, which enabled a systematic study over an exceptionally wide range of compositions. Different diffraction patterns as a function of PSiP concentration were observed in the USAXS images of the mixtures. At suitably low PSiP concentrations, the USAXS intensity profile was analyzed using the Percus-Yevick model by matching the contrast between the shell layer and IL, and the swollen structure of the shell and "effective diameter" of the PSiP were evaluated. This result confirms that under sufficiently low pressures below and near the liquid/crystal-threshold concentration, the studied PSiP can be well described using the "hard sphere" model in colloidal science. Above the threshold concentration, the PSiP forms higher-order structures. The analysis of diffraction patterns revealed structural changes from disorder to random hexagonal-closed-packing and then face-centered-cubic as the PSiP concentration increased. These results are discussed in terms of thermodynamically stable "hard" and/or "semi-soft" colloidal crystals, wherein the swollen layer of the concentrated polymer brush and its structure play an important role.

Visualization of Individual Images in Patterned Organic-Inorganic Multilayers Using GISAXS-CT.

Using grazing-incidence small-angle scattering (GISAXS) with computed tomography (CT), we have individually reconstructed the spatial distribution of a thin gold (Au) layer buried under a thin poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) layer. Owing to the difference between total reflection angles of Au and PS-b-P2VP, the scattering profiles for Au nanoparticles and self-assembled nanostructures of PS-b-P2VP could be independently obtained by changing the X-ray angle of incidence. Reconstruction of scattering profiles allows one to separately characterize spatial distributions in Au and PS-b-P2VP nanostructures.

ε subunit of Bacillus subtilis F1-ATPase relieves MgADP inhibition.

MgADP inhibition, which is considered as a part of the regulatory system of ATP synthase, is a well-known process common to all F1-ATPases, a soluble component of ATP synthase. The entrapment of inhibitory MgADP at catalytic sites terminates catalysis. Regulation by the ε subunit is a common mechanism among F1-ATPases from bacteria and plants. The relationship between these two forms of regulatory mechanisms is obscure because it is difficult to distinguish which is active at a particular moment. Here, using F1-ATPase from Bacillus subtilis (BF1), which is strongly affected by MgADP inhibition, we can distinguish MgADP inhibition from regulation by the ε subunit. The ε subunit did not inhibit but activated BF1. We conclude that the ε subunit relieves BF1 from MgADP inhibition.

Nonuniversal nature of dynamic critical anomaly in polymer solutions.

Critical anomaly of viscosity has been studied for ideal polymer solutions, focusing on its dependence on the molecular weight of polymer M(w). According to the conventional understanding that polymer solutions should belong to the same dynamic universal class as classical fluids, the critical exponent of viscosity y(c) should be a universal constant (approximately 0.04). Contrary to this, we find that y(c) significantly decreases with increasing M(w). This unusual behavior can be explained by the dynamic coupling of critical concentration fluctuations with an additional slow viscoelastic mode intrinsic to polymer solutions. Our dynamic light scattering measurements support this picture.