Delamination of Organically Modified Layered Filler via Solid‐State Processing

Summary: Solid‐state processing for the preparation of poly(p‐phenylenesulfide) (PPS‐) based nano‐composites having finely dispersed layered fillers was conducted. The mixture of PPS and organically modified layered filler (OMLF) (95/5 wt./wt.) was subjected to the processing using thermostated hot‐press at 150 °C, below T_m of PPS (i.e., PPS is still at the solid‐state), and applying pressures of 33 MPa for 30 s. The mixture exhibited disorder and delaminated layer structure with the thickness of 10–20 nm into the PPS matrix. In contrast, a nano‐composite prepared by melt compounding at 300 °C for 3 min showed large stacked silicate layers in the PPS matrix. The processing led to delamination of the silicate layers and attained the discrete dispersion.

TEM bright field image and FFT spectrum of a solid‐state processed PPS nano‐composite.     

Induction and inversion of chirality in poly‐L‐lysine and methyl orange complex

The mechanism of complexation of poly‐L‐lysine (PLL) with methyl orange (MO) and the appearance of induced circular dichroism (ICD) were investigated as a function of dye concentration and temperature and compared with that of the PLL‐ethyl orange complex. The formation of stoichiometric complexes with uniform size and intensities of ICDs depended on the length of alkyl groups (methyl and ethyl) as determined from quartz crystal microbalance measurement, absorption spectra, and CD spectra data. Furthermore, at constant PLL concentration, a dependence of the inversion of the ICD on the MO concentration (CMO) was observed in the PLL‐MO complexes, which to our knowledge has not been reported for a constant dye concentration system. The positive ICD in the PLL‐MO complexes observed at CMO lower than 2.0 × 10^?5 M showed reversible changes in response to heating and cooling, whereas the negative ICD in PLL‐MO complexes observed at higher CMO inverted to positive ICD values in response to a decrease in temperature. These results demonstrate the alkyl group substituent in the dye, dye concentration, and temperature play important roles in the formation of PLL‐azo dye complex and ICD appearance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Characterization of heat-induced interaction of neutral liposome with lipid membrane of Streptomyces griseus cell

The interaction between the neutral 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) liposomes and cell membrane of Streptomyces griseus induced by the heat treatment at specific temperature was investigated, focusing on the internalization of the neutral POPC liposomes with S. griseus cells. In an attempt to clarify the modes of liposome internalization, various kinds of inhibitors of endocytotic pathways were used to treat S. griseus cells. The efficiency of the heat treatment on liposome–cell membrane interactions was finally characterized based on the hydrophobic, electrostatic interactions and hydration effect. In fact, the internalization of the neutral liposomes into these cells was found to show higher rate and greater amount at higher temperatures. The kinetic study showed that the maximum amount of the internalized liposomes was, respectively, 469 × 10⁵ and 643 × 10⁵ liposomes/cell at 37 and 41 °C. The internalization of the neutral liposomes induced by the heat treatment was characterized, implying that the endocytosis occurred. The interactions involving the internalization, adsorption, and fusion of these liposomes with S. griseus cells were mainly contributed by the hydrophobic interaction and the unstable hydrogen bonds caused by the loss of water of surface hydration of cell membrane rather than the electrostatic interaction under the specific heat condition.     

Excited states and electronic spectra of extended tetraazaporphyrins

Electronic excited states, electronic absorption, and magnetic circular dichroism (MCD) spectra of free-base tetraazaporphyrin (TAP), phthalocyanine (Pc), naphthalocyanine (Nc), and anthracocyanine (Ac) were studied by quantum chemical calculations using the symmetry-adapted cluster-configuration interaction (SAC-CI) method. Not only optically allowed states including the Q- and B-bands but also optically forbidden states were calculated for transitions whose excitation energies were lower than 4.5 eV. The present SAC-CI calculations consistently assigned the absorption and MCD peaks as optically allowed π→π(?) excitations, although these calculations using double-zeta basis limit quantitative agreement and discussion. For Nc and Ac, excited states beyond the four-orbital model appeared in the low-energy region. The low-energy shifts of the Q-bands with the extension of molecular size were explained by the orbital energies. The splitting of the Q-bands decreases with extension of the molecular size. This feature was reproduced by the SAC-CI calculations but the configuration interaction with single excitations and time-dependent density functional theory calculations failed to reproduce this trend. Electron correlation in the excited states is important in reproducing this splitting of the Q-bands and in describing the energy difference between the B(2u) and B(3u) states of free-base porphyrins.     

Intramolecular SN'-type aromatic substitution of benzylic carbonates at their para-position

The benzylic carbonates, which connect with an active methine through an o-phenylene tether at their meta-position, are cyclized by Pd(η(3)-C(3)H(5))Cp-S-Phos catalyst, yielding 3-methyl-9,10-dihydrophenanthrenes. In the catalytic cyclization, the internal nucleophile attacks not the ortho-carbon but the para-carbon of the benzylic ester. The [3 + 2] cycloaddition of m-(silylmethyl)benzyl carbonates with alkylidene malonates was developed from the palladium-catalyzed intramolecular S(N)'-type aromatic substitution.     

Catalytic asymmetric hydrogenation of 3-substituted benzisoxazoles

A variety of 3-substituted benzisoxazoles were reduced with hydrogen using the chiral ruthenium catalyst, {RuCl(p-cymene)[(R,R)-(S,S)-PhTRAP]}Cl. The ruthenium-catalyzed hydrogenation proceeded in high yield in the presence of an acylating agent, affording α-substituted o-hydroxybenzylamines with up to 57% ee. In the catalytic transformation, the N-O bond of the benzisoxazole substrate is reductively cleaved by the ruthenium complex under the hydrogenation conditions. The C-N double bond of the resulting imine is saturated stereoselectively through the PhTRAP-ruthenium catalysis. The hydrogenation produces chiral primary amines, which may work as catalytic poisons, however, the amino group of the hydrogenation product is rapidly acylated when the reaction is conducted in the presence of an appropriate acylating agent, such as Boc?O or Cbz-OSu.     

Direct numerical simulations of electrophoresis of charged colloids

We propose a numerical method to simulate electrohydrodynamic phenomena in charged colloidal dispersions. This method enables us to compute the time evolutions of colloidal particles, ions, and host fluids simultaneously by solving Newton, advection-diffusion, and Navier-Stokes equations so that the electrohydrodynamic couplings can be fully taken into account. The electrophoretic mobilities of charged spherical particles are calculated in several situations. The comparisons with approximation theories show quantitative agreements for dilute dispersions without any empirical parameters; however, our simulation predicts notable deviations in the case of dense dispersions.     

Electronic spectra and photodissociation of vinyl chloride: a symmetry-adapted cluster configuration interaction study

The vertical absorption spectrum and photodissociation mechanism of vinyl chloride (VC) were studied by using symmetry-adapted cluster configuration interaction theory. The important vertical pi --> pi* excitation was intensively examined with various basis sets up to aug-cc-pVTZ augmented with appropriate Rydberg functions. The excitation energy for pi --> pi* transition obtained in the present study, 6.96 eV, agrees well with the experimental value, 6.7-6.9 eV. Calculated excitation energies along with the oscillator strengths clarify that the main excitation in VC is the pi --> pi* excitation. Contrary to the earlier theoretical reports, the results obtained here support that the C-Cl bond dissociation takes place through the n(Cl-)sigma(C-Cl)* state.     

Effect of Bi surfactant on the heteroepitaxial growth in Fe/Cr(100) multilayers

This study was to investigate the surfactant effect of Bi on the heteroepitaxial growth of Fe/Cr(100) multilayers by reflection high-energy electron diffraction (RHEED) measurements. With predeposition of submonolayer Bi on Fe(100) prior to evaporation of Fe/Cr multilayer, more long-lasting RHEED intensity oscillations were observed. This implies that the layer-by-layer growth of Fe/Cr multilayer is enhanced. The observations of grazing incidence X-ray reflectivity confirmed that the interface structures of Fe/Cr multilayer with Bi were sharper than that of multilayer without Bi. The study was also to investigate the magnetotransport properties between Bi surfactant-mediated multilayers and normal ones. The magnetoresistance (MR) ratio of the multilayers was enhanced by predeposition of Bi.