T. Takeda

Neutron spin–echo investigations of membrane undulations in complex fluids involving amphiphiles

Abstract The intermediate functions I ( Q , t ) obtained from neutron spin–echo (NSE) experiments were well fitted to I(Q,t)=I(Q,0) exp [−(Γt) 2/3 ] for the bicontinuous microemulsion and the lamellar phases of the C 12 E 5 / n -octane/water system and also for the lamellar phase of the DPPC/water/CaCl 2 system. The relaxation rate Γ increased as Q 3 . These results support the theory presented by Zilman and Granek [Phys. Rev. Lett. 77 (1996) 4788]. Bending modulus of the membrane ϰ was estimated in the C 12 E 5 / n -octane/water system and in the DPPC/water/CaCl 2 system using their theory.

Bending modulus of lipid bilayers in a liquid-crystalline phase including an anomalous swelling regime estimated by neutron spin echo experiments

Abstract.Membrane fluctuations of dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) were investigated by neutron spin echo spectroscopy. The intermediate structure factor was analyzed in terms of the model proposed by Zilman and Granek (Phys. Rev. Lett. 77, 4788 (1996)), and the bending modulus of lipid bilayers was derived. The hardening of a lipid bilayer upon approaching the main transition point in the anomalous swelling regime was observed, which naturally connects the bending modulus in the gel phase below the main transition temperature.

Temperature and pressure effects on structural formations in a ternary microemulsion

Small angle neutron scattering experiments were conducted on a temperature-induced phase transition in a ternary microemulsion composed of AOT (dioctyl sulfosuccinate sodium salt), D2 O and n-decane and the results were compared with those of pressure-induced one. Although the static features of both the temperature- and the pressure-induced phase behaviour were similar, a temperature dependence of its characteristic repeat distance at high temperature was quite different from a pressure dependence of that at high pressure. Neutron spin echo experiments were also performed on both the phase transitions. The dynamics of the high temperature phase was different from that of the high pressure phase. These results indicated that the effect of pressure on the structural formation was different from that of temperature.

Advanced Soft Material Beamline Consortium at SPring-8 (FSBL)

Soft materials, such as polymers and fibers, are key industries in Japan and play a significant role in our daily lives [1–3]. These materials also contribute to our modern society in a wide range of applications, such as in aircrafts and automobiles, and in a diverse variety of medical, electronic, and optical devices. In the future, it is expected that polymer science and technology will continue to expand and play an important role in research related to the environment [4], energy science [5], green technology [6], and biotechnology [7].

Neutron Spin Echo Study on Slow Dynamics of Lipid Bilayers in the DPPC/D2O/CaCl2 System

In order to study slow dynamics of lipid bilayers, neutron spin echo (NSE) experiments were carried out on the dilute lamellar phase in the DPPC/D2O/CaCl2 system. From the NSE results, we estimated the bending modulus κ of the bilayer using the theory presented by Zilman and Granek (Phys. Rev. Letters 77 (1996) 4788). The estimated values of κ decrease monotonically with increasing temperature and with increasing the lamellar repeat distance d1. They depend strongly on d1 though d1 is longer than 500A. We discuss validity of the theory for the analysis of the NSE results.

NEUTRON SPIN ECHO STUDIES ON DYNAMICS OF POLYMERIC MICELLES

Abstract Neutron spin echo measurements were performed on polymeric micelles consisting of deuterated polystyrene (d-PS)-polyisoprene (PI) diblock copolymers in dilute and concentrated solutions. The scattering length density of the core of the micelles matched to the solvent so that dynamics of polymer chains in the corona were measured. The observed intermediate scattering functions in the dilute solution were analyzed by the theory for tethered chains proposed by de Gennes. In the concentrated solutions, motional slowing down was observed, which may be caused not only by increase of the viscosity but also by decrease of the osmotic compressibility.

Instrumentation of SAXS for the Analysis of Heterogeneous Structure in Polymer

Polymer materials have hierarchal structure in the very wide range of scale. It is well known that the property is dependent on the hierarchical structure. In order to improve the performance of the materials, clarifying the hierarchical structure in a wide range and the feed back to the manufacturing process are important. However, it is difficult to clarify the hierarchical heterogeneous structure of polymer materials using only single method. Therefore the combination of microbeam smalland wideangle X-ray scattering (SAXS/WAXS) is useful for evaluation of the hierarchical heterogeneous structural of polymer materials. The BL03XU, in alias, FSBL, in SPring-8 was constructed by consortium of industrial and academic groups and has been used from 20101),2). Structure characterization of advanced materials in the industrial field has been carried out using microbeam SAXS/WAXS method. In addition to the description of the SAXS/WAXS measurement system at BL03XU, we will report on the local structural evaluation of carbon fiber (CF). A hierarchal heterogeneous structure of CFs was visualized in the space resolution of 1 μm using a microbeam and an X-ray imaging technique. The image contrasts were identified by the difference in peak positions corresponding to the void size, the peak width corresponding to the crystallite size, and intensities corresponding to the amount of crystallites and voids. The X-ray scattering images of high-modulus CF are shown in a figure. Nanometer-size voids estimated by SAXS are abundant in the center of a fiber, on the other hand, the crystallite is abundant in the vicinity of a surface was revealed. It is suggested that the voids were generated near the center of the fiber to relax the strain during the crystallization process from the surface during the graphitization of fibers. We succeeded in visualizing the distribution of voids and crystallite of a few nanometers, which cannot be observed by an X-ray transmission imaging method.

Detector Area Expansion at iNSE Neutron Spin Echo Spectrometer

A 2D-detector and an analyzer had been installed on iNSE neutron spin echo spectrometer for wide-area data acquisition. Since the areas of the 2nd π/2 spin flipper and the last Fresnel coil were not wide enough for a full area measurement, only the center area of the detector had been used. In 2006, we renewed the spin flipper and the Fresnel coils to expand the detection area. To improve the efficiency of the data acquisition, we proposed a novel method for phase correction of NSE signals. Finally, the efficiency of the NSE measurement increased by approximately one order of magnitude.

Temperature‐ and Pressure‐dependences of a Bending Modulus of Surfactant Monolayers in a Ternary Microemulsion Composed of AOT / D2O / decane

A bending modulus of surfactant monolayers in a microemulsion system composed of AOT, D2O and deuterated decane were investigated by means of neutron spin echo. In this system, a water‐in‐oil droplet structure at ambient temperature and pressure decomposes into two‐phases both with increasing temperature and pressure. However, the bending modulus slightly decreased with increasing temperature while it increased with increasing pressure. This behavior was explained in terms of a microscopic model proposed by Wurger (Phys. Rev. Lett. 85 (2000) 337). It was confirmed that an increase of an interaction between hydrocarbon tails of AOT molecules with increasing pressure could be an origin of the pressure‐induced phase transition.

Volume Fraction Dependence of the Structure Function in Binary Systems Undergoing Phase Separation

Various binary systems, that are initially homogeneous, can be brought by a sudden change of temperature or pressure into an unstable state towards the decomposition of the constituents. The structure function S(k,t), which characterizes the inhomogeneous structure and evolves with real time t, has been found to be expressed by a timeindependent scaling function \(\tilde{s}(x)\) in a form