Distribution analysis of epoxy groups in polymers by derivatization-electron probe X-ray microanalysis.

An analytical method, referred to as "derivatization-electron probe X-ray micro-analysis (XMA)", has been developed to determine the distribution of a small amount of the functional groups in a polymer. The suitable conditions for the derivatization reaction with epoxy groups, which contribute to the hardening reactions of polymers, were investigated. It was found that epoxy groups in polymers were derivatized selectively using gas-phase esterification with hydrochloric acid (HCI). The most suitable amount of HCl in a 50 ml vial was 300 microl. After setting a sample in the vessel without directly contacting the reagent, by reacting the reagent and the sample at 25 degrees C for 1 h, the highest reaction yield and selectivity were obtained. By derivatization-XMA using this reaction condition, the measurement of the distribution of epoxy groups in the polymer became feasible. Actual applications to a depth analysis of epoxy groups in the hardened acrylic coating and epoxy resin proved that this method is useful for the characterization of polymers and for the study of the hardening reaction of polymers.     

1:1 complexes of dimethylthio- and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides with CuBr2 as a new type of pi/d molecular system

The reaction of dimethylthio- (1) and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides (2) with CuBr2 gave 1:1 complexes between the donors and CuBr2, 1.CuBr2 and 2.CuBr2, in which the Cu atom of CuBr2 binds to the thiocarbonyl S atom in 1 and 2. The electrical conductivity (sigma) of 1.CuBr2 at room temperature was ca. 10(-5) S cm-1, while a comparatively high value of 4.0 S cm-1 was obtained for 2.CuBr2, whose temperature dependence of sigma exhibited, however, semiconducting behavior with a very small activation energy of 0.18 eV. The observed paramagnetic susceptibilities (chi p's) of the Cu complexes were composed of both a component due to the localized Cu spins obeying the Curie-Weiss law and a temperature-independent chi p due to the conducting pi electrons on the 1- or 2-stacked columns. From the Curie constants obtained, the degrees of intramolecular electron transfer from 1 and 2 to CuBr2 moieties were estimated at ca. 90% and 60%, respectively. The small, negative Weiss temperature suggest very weak antiferromagnetic interactions among the Cu spins on the CuBr2 moieties.     

Oxygen induced surface structure of Mo(1 1 0) studied by scanning tunneling microscopy

The oxygen induced surface structures formed on Mo(1 1 0) by oxygen exposure at 1300 K in UHV has been studied by scanning tunneling microscopy (STM). Two kinds of oxygen-adsorbed surface structures are observed. One consists of one-dimensional rows running along or directions at substrate molybdenum lattices, and another shows more complex structure including discrete arrangement of large protrusions and zig-zag alignments of small protrusions. This complex structure is probably a further oxygen-adsorbed structure than the well-known p(2 × 2) structure of 0.3 ML coverage. On the basis of STM image, an atomic model is proposed, where adsorbed oxygen atoms occupy both long-bridge and the quasi-threefold sites of molybdenum lattice (0.4 ML coverage). This structure is presumed to be a transient state during site-conversion with increase of oxygen exposure.     

Infrared study of proton-deuteron mutual diffusion in a CsHSO4/CsDSO4 solid under high pressure

Proton-deuteron mutual diffusion in a CsHSO₄/CsDSO₄ solid at 373 K was examined up to 3 GPa by an infrared mapping measurement. Phases HPHT1 and HPHT2 appeared at 1.5 and 2.3 GPa, respectively, after heating. These phases were found to be stable at room temperature, while phase IV, which appeared on compression at room temperature, was metastable. The pressure dependence of the proton-deuteron mutual diffusion coefficient was determined from the temporal change in the deuteron distribution of the solid. The coefficient decreased from 7×10⁻¹⁶ to 1×10⁻¹⁶ m²/s during the transition from phase II to HPHT1 at 1.5 GPa, and showed no significant change during the transition to phase HPHT2. These results suggested that in addition to the hydrogen bond length, other structural factors might also have had an influence on the rate of diffusion.     

Upconversion luminescence in Er-doped germanate-oxyfluoride and tellurium-germanate-oxyfluoride transparent glass-ceramics

Upconversion luminescence has been studied for Er³⁺ in a germanate-oxyfluoride and a tellurium-germanate-oxyfluoride transparent glass-ceramic using 800 nm excitation. Significantly increased upconversion luminescence was observed from transparent glass-ceramics compared with that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm from ⁴S_3/2 state and a weaker red emission centered at 662 nm from ⁴F_9/2 state generally seen from Er³⁺-doped glasses, a violet emission centered at 410 nm from ²H_9/2 state and a near-ultra-violet emission centered at 379 nm from ⁴G_11/2 state were also observed from transparent glass-ceramics. The upconversion luminescence of Er³⁺ ions in transparent glass-ceramics revealed sharp Stark-splitting peaks generally seen in a crystal host. The increased upconversion efficiency is attributed to the decreased effective phonon energy and the increased energy transfer between excited ions when Er³⁺ ions were incorporated into the precipitated β-PbF₂ nanocrystals.     

Method for measuring the phase error distribution of a wideband arrayed waveguide grating in the frequency domain

We describe a method for measuring the phase error distribution of an arrayed waveguide grating (AWG) in the frequency domain when the free spectral range (FSR) of the AWG is so wide that it cannot be covered by one tunable laser source. Our method is to sweep the light frequency in the neighborhoods of two successive peaks in the AWG transmission spectrum by using two laser sources with different tuning ranges. The method was confirmed experimentally by applying it to a 160 GHz spaced AWG with a FSR of 11 THz. The variations in the derived phase error data were very small at +/-0.02 rad around the central arrayed waveguides.     

Heat transfer and fluid dynamics of air–water two-phase flow in micro-channels

Heat transfer, pressure drop, and void fraction were simultaneously measured for upward heated air–water non-boiling two-phase flow in 0.51 mm ID tube to investigate thermo–hydro dynamic characteristics of two-phase flow in micro-channels. At low liquid superficial velocity j_l frictional pressure drop agreed with Mishima–Hibiki’s correlation, whereas agreed with Chisholm–Laird’s correlation at relatively high j_l. Void fraction was lower than the homogeneous model and conventional empirical correlations. To interpret the decrease of void fraction with decrease of tube diameter, a relation among the void fraction, pressure gradient and tube diameter was derived. Heat transfer coefficient fairly agreed with the data for 1.03 and 2.01 mm ID tubes when j_l was relatively high. But it became lower than that for larger diameter tubes when j_l was low. Analogy between heat transfer and frictional pressure drop was proved to hold roughly for the two-phase flow in micro-channel. But satisfactory relation was not obtained under the condition of low liquid superficial velocity.     

Rheology and morphology change with temperature of SEBS/hydrocarbon oil blends

The effect of hydrocarbon oil incorporation on the rheological and phase behaviors of poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) has been investigated. SEBS‐A1 (neat SEBS) shows a presence of very long relaxation time mode even at the highest temperature carried out here. On the other hand, G′ of SEBS‐A3 (oil concentration = 50 wt %) drastically decreases with increase of temperature at a critical temperature, which can be assigned to be order–disorder transition (ODT). The critical temperature was determined by two rheological criteria. Incorporation of hydrocarbon oil affects the ODT temperature. The rheological response is very sensitive to a few temperature increases around the ODT temperature. Above the critical temperature, G′ finally yields the terminal flow in the low frequency range. The morphological observation at various temperatures was determined using atomic force microscopy (AFM) equipped with environmental controller. This enabled in situ observation of structural change of SEBS induced by temperature and phase transition. We found that the layered texture, mostly aligned along the surface can be seen for SEBS‐A1 ranging from room temperature to 230 °C, though the image contrast reduced by an increase of temperature. SEBS‐A3 showed sphere domains at room temperature and also remains the structure at a critical temperature. The phase separated structure disappeared almost completely above ODT temperature, which was confirmed by the rheologial criteria. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 955–965, 2009     

Polymer electrolyte membrane based on poly(ether sulfone) containing binaphthyl units with pendant perfluoroalkyl sulfonic acids

A novel poly(ether sulfone) containing binaphthyl units with pendant perfluoroalkyl sulfonic acids ( BNSH‐PSA ) was developed for a polymer electrolyte membrane (PEM). The BNSH‐PSA was prepared by the aromatic nucleophilic substitution reaction of 1,1′‐binaphthyl‐4,4′‐diol and 4,4′‐dichlorodiphenylsulfone, followed by the bromination with bromine, and then the Ullman coupling reaction with potassium 1,1,2,2,‐tetrafluoro‐2‐(1,1,2,2‐tetrafluoro‐2‐iodoethoxy) ethanesulfonate ( PSA‐K ). The ion exchange capacity (IEC) of BNSH‐PSA was estimated to be 1.91 mequiv/g, which corresponded to full conversion to the perfluroalkyl sulfonic acids. The BNSH‐PSA membrane prepared by solution casting showed high oxidative and dimensional stability. High proton conductivity comparable to the Nafion 117 membrane was accomplished in the range of 30–95% relative humidity (RH) due to the high acidity of the perfluoroalkyl sulfonic acids. Furthermore, atomic force microscopic observation supported the formation of the phase‐separated structure that the hydrophilic domains were well dispersed and connected to each other. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011