Taiki Hoshino

Surface tension of room temperature ionic liquids measured by dynamic light scattering

Using dynamic light scattering techniques, we obtained the surface tension sigma, surface excess entropy S(sigma), surface excess enthalpy H(sigma), and viscosity eta for the following seven room temperature ionic liquids in a wide temperature range from 30 to around 140 degrees C: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, and 1-octyl-3-methyl imidazolium hexafluorophosphate. We have found that sigma increases systematically with decreasing the anion size and the alkyl side chain length. On the other hand, S(sigma) and eta increase with decreasing the anion size but decrease with decreasing the alkyl chain length. H(sigma) seems to decrease with increasing the anion size, but it has no clear dependence on the alkyl chain length. We discuss the bulk and surface properties, referring to the Coulomb interactions and van der Waals interactions.

X-ray photon correlation spectroscopy using a fast pixel array detector with a grid mask resolution enhancer

The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy experiments.

Sound Velocity and Attenuation in the Semiconductor-Metal Transition Region of Fluid Selenium

We have measured the sound velocity, v , and sound attenuation, α, in fluid selenium up to 1700 °C and 1666 bar including the semiconductor–metal (SC–M) transition region for the first time. The ultrasonic measurements were performed by an ultrasonic pulse transmission/echo method. A coherent phase-detection technique was used for a precise velocity measurement. Anomalous changes in the temperature dependence of v were observed at pressures above 294 bar. The inflections of v were closely related to the electronic properties and served as good indicators of the SC–M transition region except for the vicinity of the liquid–gas critical point. v along isochores decreases with increasing temperature in the transition region, which means an increase in density fluctuations. Moreover, in addition to the critical attenuation, we also observed an anomalous increase in α in the transition region. The increase in α was attributed to an increase in bulk viscosity. On the basis of these results, we point out that a m...

Characterization of Surface Microstructures on Bio-based Polymer Film Fabricated with Nano-imprint Lithography by Synchrotron Radiation Small Angle X-ray Scattering

Nano-imprint lithography (NIL) is a simple, low cost and high-resolution patterning method. However the precise evaluation method of nano-imprinted structure has not been established. Synchrotron radiation small angle X-ray scattering (SR-SAXS) measurement is a nondestructive and high resolution characterization method. In this study, we attempt to fabricate nanostructures on the poly(lactic acid) (PLA) film by NIL and evaluated with microscopic and scattering techniques. The mold with line/space pattern was used for NIL. Scanning electron microscope observation confirmed the formation of surface nano-structure in large areas. Also, nano-imprinted PLA film was evaluated using SR-SAXS measurement. The scattering patterns obtained from nano-imprinted PLA films were clearly observed up to higher order scattering spots. These results suggested that highly regular structure was fabricated on the surface of PLA films.

X-ray Photon Correlation Spectroscopy of Silica Particles Grafted with Polymer Brush in Polystyrene Matrix

X-ray photon correlation spectroscopy system was setup at SPring-8, BL19LXU, and the partial coherence scattering data from the silica particles grafted with polymer brush in polystyrene matrix were measured. Firstly, the static speckle patterns were checked. Below the glass transition temperature of polystyrene (Tg), speckles were clearly observed, on the other hand, above Tg, the scattering patterns became smooth and speckles were hardly observed. These variances of the speckle patterns result from the particle motion. Secondly, from the time variance of the speckle data, time autocorrelation functions g2(q,t) are calculated. While the flat behaviour of g2(q,t) without relaxation were observed below Tg, the relaxation behavior with relaxation time~100–101 were observed above Tg

Static and Dynamic Scattering from Polysulfobetaine Immobilized on Silica Nanoparticle in Ionic Liquid

Monodisperse silica nanoparticles were immobilized with poly[3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate)] (SiNP-PMAPS) by surface-initiated atom transfer radical polymerization. SiNP-PMAPS was characterized in 1-hexyl-3-methylimidazolium chloride (HMImCl) solution by dynamic light scattering (DLS) and synchrotron small angle X-ray scattering (SAXS) measurements. The relaxation spectrum of DLS and SAXS profile for SiNP-PMAPS solutions showed a unimodal distribution attributed to the homogeneous dispersion of SiNP-PMAPS in the HMImCl without any aggregations. The scattering factor from the SiNP-PMAPS in HMImCl was described by the core-shell model considering interacting excluded-volume chains and assuming Schulz distributed core with the thickness of polymer layer of 56 nm.

Meso-scale fluctuations in liquid chalcogens near the metal-nonmetal transition

Liquid Te-Se mixtures exhibit a metal-nonmetal (M-NM) transition, which is accompanied by various anomalies in thermodynamic properties such as the thermal expansion coefficient, compressibility and sound attenuation coefficient. These anomalies may be explained by the coexistence and the relaxation of the metallic and non-metallic regions in the liquid, and it is interesting to study the space and time-structure of the meso-scale fluctuations. In the present work, we performed small angle neutron scattering (SANS) and neutron spin-echo (NSE) measurements for liquid Te-Se mixtures near the M-NM transition. We observed that SANS intensity increases with temperature. The NSE intermediate scattering function can be expressed by a superposition of fast and slow exponential relaxation process, whose relaxation times are estimated as Tfast ~ 0.1nsec and Tslow > 10 nsec, respectively. The slow component becomes dominant in the low-Q region, and this process may be related to the anomalous sound attenuation.