Thermal cured epoxy resins using certain calixarenes and their esterified derivatives as curing agents

The acetyl esterified calixarene (CA) derivatives were prepared from calix[4]resorcinarene (CRA), and p‐tert‐butylcalixarene (BCA[n], n = 4, 6, 8), respectively. Using these CA derivatives as curing agents, the thermal curing reactions of two multifunctional epoxy resins (jER 828, 186 g/equiv., and ESCN, 193.7 g/equiv.) were investigated. The temperatures of glass transition (T_g) and decomposition (T) were measured by DSC and TGA, respectively. Based on the yields, T_gs, and T_ds of the thermal cured jER 828 epoxy resin with CRA‐E100, the curing conditions were optimized to be tetrabutylphosphonium bromide (TBPB) as catalyst in NMP at 160 °C for 15 h. Under this curing condition, the cured materials of jER 828 or ESCN using various CA derivatives as curing agents were prepared. Except for BCA4 derivatives, the yields of thermal curing reaction were higher than 90%. T_gs and Ts of the resultant cured materials were in the range of 113–248 °C and 363–404 °C, respectively. These results mean that the cured epoxy resins with excellent T_gs were successfully formed by using CA derivatives as curing agents. It was also found that the T_gs of cured epoxy resins were strongly affected by the degree of esterification of CA derivatives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1931–1942, 2010     

Characterization of certified reference material for quantification of polychlorinated biphenyls and organochlorine pesticides in fish

Fish certified reference material (CRM), NMIJ CRM 7404-a, for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) was developed by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial Science and Technology. Fish samples (Japanese seabass) used for the preparation of the CRM were collected from Tokyo Bay, and the edible part was freeze-dried, pulverized, sieved, homogenized, and sterilized by γ-irradiation. This sample is in the form of a powder comprising approximately 10 g stored in a brown glass bottle. The certification was carried out using multiple analytical methods such as pressurized liquid extraction, Soxhlet extraction, saponification, and homogenization to ensure the reliability of analytical results; the certified values of target PCBs (PCB 28, PCB 70, PCB 105, PCB 153, and PCB 170) and OCPs (trans-nonachlor, dieldrin, p,p′-DDE, p,p′-DDT, and p,p′-DDD) were 1.05–14.0 μg kg⁻¹ and 1.57–18.0 μg kg⁻¹ for PCBs and OCPs, respectively. This is the first fish powder CRM in which PCBs and OCPs were determined by isotope dilution mass spectrometry.     

Observation of charged excitons in hole-doped carbon nanotubes using photoluminescence and absorption spectroscopy

We report the first observation of trions (charged excitons), three-particle bound states consisting of one electron and two holes, in hole-doped carbon nanotubes at room temperature. When p-type dopants are added to carbon nanotube solutions, the photoluminescence and absorption peaks of the trions appear far below the E11 bright exciton peak, regardless of the dopant species. The unexpectedly large energy separation between the bright excitons and the trions is attributed to the strong electron-hole exchange interaction in carbon nanotubes.     

Non-synchronous oscillations in four-dimensional nonlinear semelparous Leslie matrix models

In a certain class of semelparous Leslie matrix models, either a positive equilibrium is stable and an invariant set on the boundary of the nonnegative cone is unstable or vice versa generically if the model dimension is two or three. This dynamic dichotomy is expected to be failed in the four-dimensional case. Our study focuses on a semelparous Leslie matrix model with specific nonlinearities and rigorously proves that the dynamic dichotomy does not hold in the four-dimensional case. This result is derived by showing that the four-dimensional semelparous Leslie matrix model can be uniformly persistent with respect to the boundary of the nonnegative cone even if there exists an unstable positive equilibrium. In such a situation, there are no missing age-classes but population oscillation occurs.     

Mass balance method for purity assay of phthalic acid esters: development of primary reference materials as traceability sources in the Japan Calibration Service System

Purity assay of high-purity materials (HPMs) of phthalic acid esters (PAEs) was carried out by means of a mass balance method. In this method, chromatographic methods such as gas chromatography-flame ionization detector (GC-FID) and/or high-performance liquid chromatography (HPLC) in combination with other methods such as Karl-Fischer (KF) titration and vacuum evaporation (VE) were applied. The sum of the impurities estimated by these methods allowed the estimation of the purity of the main component by difference. Seven PAEs with varying side chain structures and levels of impurities were analysed on a systematic way in which impurities were classified into several groups in terms of their abundance, availability of qualitative information and availability of authentic compounds, etc. The absolute quantity of each impurity was determined by GC-FID and/or HPLC based on the calibration made by the authentic compounds of impurities whenever available. The purities in mass fraction of these PAEs were certified at the National Metrology Institute of Japan (NMIJ), and the PAEs were registered as primary reference materials playing an essential role in linking the metrological traceability of the Japan Calibration Service System (JCSS) to the International System of Units (SI).     

Differences in the yields of polycyclic aromatic hydrocarbons by pressurized liquid extraction and the Japanese official method

To improve the extraction of polycyclic aromatic hydrocarbons (PAHs) from sediment samples, we optimized the conditions of pressurized liquid extraction (PLE). The yields increased as the extraction temperature increased from 100 to 190 degrees C, but the effect of increasing pressure (from 15 to 20 MPa) was small. Parameters of 190 degrees C and 20 MPa, near the maximum of the equipment, gave the highest yield. Under these conditions, the yields of 17 PAHs were 1.5 - 34 times those obtained by the Japanese official method (shaking and ultrasonic extraction with acetone at room temperature).     

Accurate Quantification of Polycyclic Aromatic Hydrocarbons in Environmental Samples Using Deuterium-labeled Compounds as Internal Standards

For the accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in environmental samples by isotope-dilution mass spectrometry (IDMS) and gas chromatography-mass spectrometry (GC-MS), we used deuterium-labeled PAHs (D-PAHs) as internal standards for microg g(-1)-level certified reference materials and corresponding calibration solutions. Although pressurized liquid extraction (PLE) causes significant biases in the analytical results for ng g(-1)-level samples (2.4 - 15%), biases in the analytical results by PLE (190 degrees C, 20 MPa, 2 cycles) were small (<2.3%) and negligible for microg g(-1)-level samples when expanded uncertainty (coverage factor k = 2) was considered.     

Trimethylsilylmethyl derivatives of thallium(III)

Some trimethylsilylmethyl derivatives of thallium(III) have higher stability and unusual coordination behavior in comparison with simple alkylthallim(III) analogs for steric reasons.