TOF-SIMS analysis of polystyrene/polybutadiene blend using chemical derivatization and multivariate analysis

Chemical imaging with high spatial resolution is one of the features of TOF-SIMS. However, degradation of the sample due to primary ion bombardment becomes problematic when the analysis area is small. Although polystyrene (PS) and polybutadiene (PB) separately show relatively distinct spectra, observation of their phase separation in PS/PB blends is difficult when the analysis area is small because degradation of both polymers and especially PS leads to disappearance of their characteristic peaks, resulting in low chemical image contrast. We therefore investigated the application of various forms of multivariate analysis (MVA) to the TOF-SIMS image data to improve the chemical image contrast. PCA, MCR, and the other forms of MVA provided improvement in contrast, but the images were still obscure and observation of phase separation remained difficult. Chemical derivatization using osmium tetroxide was also investigated, and found to give clear images of phase separation in the PS/PB blend. In quantitative determinations with MVA and chemical derivatization, PLS demonstrated the best predictive capability and chemical derivatization resulted in large deviations from both the bulk chemical composition and the determinations with MVA, particularly in regions of low PB content.     

Hilltop curvatons

We study “hilltop” curvatons that evolve on a convex potential. Hilltop curvatons evolving on the Hubble-induced potential are generic if supergravity is assumed in the theory. We do not consider curvatons whose potential is protected from O(H)$O(H)$ corrections, where H   is the Hubble parameter. We assume that the effective mass of a curvaton is expressed as mσ=cH$m_{\sigma }=cH$, where the coefficient varies within 0.2?c?5$0.2?c?5$ depending on the circumstances. A negative mass term may lead to enhancement of curvaton fluctuation, which has a significant impact on the energy bound for low-scale inflation. Using a simple curvaton model and following the conventional curvaton hypothesis, we demonstrate the generality of this enhancement.     

An Mo theoretical study on the reaction of benzocyclobutene with ethylene. Concerted vs stepwise

In an attempt to determine the reaction mechanism of the Diels-Alder type cycloaddition reaction of benzocyclobutene with dienophiles, the stabilities for the assumed intermediate structures were examined by using MINDO/3, STO-3G, and 4-31G methods. The potential energies of the ring-opening reaction of the benzocyclobutene and cycloaddition reaction of quinodimethane with a dienophile were obtained by MINDO/3 and discussed in relation to the controversial reaction mechanism of the cycloaddition, concerted vs stepwise mechanisms. The results lead to a conclusion that the reaction involves a biradical intermediate followed by a stepwise cycloaddition.     

New agents for alkoxycarbonylation of amines

Alkoxycarbonylated pyrazinols and pyrazinethiols were prepared. These compounds were shown to be convenient agents for alkoxycarbonylation of aliphatic amines.     

Syntheses and properties of halato-telechelic polyurethane-ureas from divalent metal salts of p-aminobenzoic acid,diamine, dialkylene glycols,and diisocyanate

Halato-telechelic polyurethane-ureas were synthesized from divalent metal salts of p-aminobenzoic acid, 4,4′-diaminodiphenylmethane (4,4′-methylenedianiline, MDA), dialkylene glycols, and 2,4-toluylene diisocyanate (TDI). As the divalent metal, Mg and Ca were used, and diethylene glycol and dipropylene glycol were the glycols used. The halatotelechelic polyurethane-ureas obtained showed better solubilities in dimethylformamide (DMF) and dimethylsulfoxide (DMSO) than previously reported halato-telechelic polyureas from the metal salts, MDA, and TDI. The reduced viscosities of the polyurethane-ureas in DMF and DMSO were very low at very low concentrations but increased as the concentration increased. The increase was higher in DMF having lower dielectric constant, due to lower depression of ionic association. Introducing the metal into the urethane-urea backbone resulted in a considerable decrease in decomposition temperature. In dynamic mechanical property measurements, they exhibited no sharp decrease in relative shear modulus and no peak of tan δ, probably due to aggregation of ionic groups in the polymer main chain.     

Structure and C-13 signal assignments of new methylsterols from nervilia purpurea by two-dimensional NMR spectroscopy

The structures of cyclonervilasterol (1a) and its analogs (2a, 3a, and 4a), isolated from Nervilia purpurea, were confirmed by application-of 2-D NMR spectroscopy including INADEQUATE and also their ¹³C NMR signals were assigned.     

Electron transport properties of amorphous Mg80.4Cu19.6 alloy

The Hall coefficient, thermoelectric power and electrical resistivity of the liquid quenched amorphous Mg_80.4Cu_19.6 alloy have been measured over a wide temperature range below room temperature. The 2k_F value deduced from the observed Hall coefficient agrees well with the free electron value. The thermoelectric power is positive and increases linearly with increasing temperature above approximately 180 K. The downward deviation is evident in the lower temperature range. This behaviour is in sharp contrast with the negative thermoelectric power observed in the amorphous Mg-Zn alloy. Nevertheless, the overall temperature variation of the electrical resistivity resembles the previously reported data of the amorphous Mg_72.5Zn_27.5 alloy in various aspects; (1) the room temperature resistivity value, (2) the negative TCR and its magnitude, (3) the appearance of a broad maximum at about 50 K and a minimum at about 10 K and (4) T²-dependence in the range of 10～30 K and $\text{-(T-T}{}_{\max }\text{)}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$-dependence in the range of 50～220 K. The results are discussed in connection with $\text{2k}{}_{\mathrm{F}}\text{K}{}_{\mathrm{P}}$ criterion and Mooij correlation.     

Radical terpolymerization of sulfur dioxide,hexene-1, and methyl acrylate or methyl methacrylate

The radical terpolymerization of sulfur dioxide, hexene-1, and methyl acrylate has been investigated, and from the dilution effects on composition of the terpolymer it would seem reasonable to rule out the possibility of the participation of the charge-transfer complex in the propagation process. We have also carried out terpolymerization of sulfur dioxide, hexene-1, and methyl methacrylate and obtained a terpolymer having the block nature.