Effects of Pluronics surfactants on morphology and porosity of hematite particles produced from forced hydrolysis reaction

The shape and porosity of hematite particles, produced from a forced hydrolysis reaction of acidic FeCl₃ solution, were controlled by using Pluronics as nonionic surfactants (0–4 wt.%). Pluronics possess a nominal formula of (PEO) _x –(PPO) _y –(PEO) _x . The effect of Pluronics with low hydrophilicity (PEO contents were less than 50 mol%) was small and provided spherical particles the same as that of the system without Pluronics (control system). However, Pluronics with higher hydrophilicity (PEO contents were over 50 mol%) gave ellipsoidal hematite particles. This effect on the particle morphology was enhanced by an increase in their molecular weight. On the other hand, the Pluronics possessing an opposite nominal formula [(PPO) _x –(PEO) _y –(PPO) _x ] exhibited no effect on the particle shape; it only depressed phase transformation from ?-FeOOH to hematite. Not only the morphology but also the pore size of hematite particles was controlled from nonporous to mesoporous by using Pluronics. The N₂ adsorption experiment and t-plot curve analysis revealed that the hematite particles changed from mesoporous to microporous by an increase in the concentration of Pluronics. On the other hand, in the presence of very low amounts of Pluronics molecules (0.1 wt.%), nonporous hematite particles were produced via strong aggregation of PN particles by their hydrogen bonding between hydroxyl and PEO or PPO groups. The dynamic light scattering measurement for the system with Pluronics clarified the existence of polynuclear (PN) particles with a hydrodynamic particle diameter (D _a) of ca. 40 nm after these were aged for 6 h. The size of PN particles remained constant at ca. 40 nm during aging time of 12 h～3 days, but the scattering intensity was decreased. This decrease in the scattering intensity reveals that the number of PN particles is reduced by aggregation. The transmission electron microscope, inductively coupled plasma atomic emission spectroscopy, and total organic carbon analysis measurements employed on the systems produced for ellipsoidal particles elucidated that the formation of ellipsoidal hematite particles is attributed to the adsorption of Pluronics on the surfaces of PN and growing hematite particles.     

Microscopic phase behavior of supercritical carbon dioxide + non-ionic surfactant + water systems at elevated pressures

The microscopic phase behavior of the supercritical carbon dioxide (scCO₂) + polyethylene oxide-2,6,8-trimethyl-4-nonyl ether (TMN) + water systems at about 3 wt% of TMN were investigated using a synthetic method with a microscope. The two types of TMN (TMN-3 and TMN-10) used in this work had molecular weight distributions caused by the distribution of the number of ethylene oxide groups. Two different types of phase transition were observed when pressure was decreased gradually at a constant temperature from the high pressure at which the transparent phase was observed to the low pressure at which the separate vapor–liquid phases were observed for the scCO₂ + TMN-3 + water system at 3 wt% of TMN-3. The transparent phase was colorless under all experimental conditions and the phase transition from a transparent phase to a turbidity phase with small, dispersed droplets was observed at the higher side phase transition (higher phase transition pressure). As the pressure continued to decrease, another phase transition was observed from the phase with small droplets to a state with an accelerating aggregation of droplets (lower phase transition pressure). In the turbidity phase between the higher and the lower phase transition, the degree of turbidity became higher with decreasing pressure. On the other hand, in the phase observed below the lower phase transition, a new liquid phase adhered to the sapphire windows and the wall inside the optical cell.     

Diastereoselective protonation on a radical anion in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane

Diastereoselectivity in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane in the presence of phenanthrene was dependent on the structures and stoichiometry of the added carboxylic acids. Diastereoselectivity increased up to 72% by the addition of equimolar amount of l-lactic acid based on the alkene.     

Ion-pair structure of vaporized ionic liquid studied by matrix-isolation FTIR spectroscopy with DFT calculations: a case of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate

The matrix-isolation infrared spectrum of a thermally evaporated ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][OTf]), was measured by FTIR spectroscopy and analyzed with the aid of DFT calculations. The main chemical species in the observed IR spectrum was mainly identified as the 1:1 cation-anion pair, which corresponds to the second stable ion-pair structure bonded through five hydrogen bonds between three O atoms of the anion side and four H atoms of the cation.     

Nuclear quadrupole resonance of norephedrine

Toward searching for illegal drugs, we investigated the pulsed nuclear quadrupole resonance (NQR) response of ¹⁴N in (1R,2S)-(-)-norephedrine, based on the predictions of quantum chemical calculations. Two pairs of spectral lines (ν₊=3.089, 3.093 MHz and ν₋=2.594, 2.608 MHz) were observed despite its molecule structure having only a single nitrogen atom. This indicates that the molecular crystal has two nonequivalent nitrogen atoms in the unit cell. The temperature dependence of the NQR frequencies and relaxation properties were investigated for the purpose of accurate remote sensing of the drugs. The NQR frequency shift was approximately 0.23 kHz/K around room temperature. The spin-lattice relaxation and spin-phase memory times were 5.2–10.2 ms and 0.6–1.5 ms, respectively.     

Electrochemically stable fluorohydrogenate ionic liquids based on quaternary phosphonium cations

Fluorohydrogenate ionic liquids of quaternary phosphonium cations, tri-n-butylmethylphosphonium (P₄₄₄₁) fluorohydrogenate, tetra-n-butylphosphonium (P₄₄₄₄) fluorohydrogenate, and tri-n-butyl-n-octylphosphonium (P₄₄₄₈) fluorohydrogenate, have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium chloride precursors. All the obtained salts have melting points below room-temperature with a vacuum-stable composition of P_444m(FH)_2.3F (m = 1, 4, and 8) and were characterized by density, conductivity, and viscosity measurements. Linear sweep voltammetry with a glassy carbon working electrode shows that the P_444m(FH)_2.3Fs have wide electrochemical windows exceeding 5.2 V. In particular, P₄₄₄₁(FH)_2.3F has an electrochemical window of 6.0 V, which is the widest among fluorohydrogenate ionic liquids reported to date. The thermal stability of these ionic liquids is also improved compared to the salts of N-heterocyclic ammonium cations.     

Effect of Anomeric Linkage on the Sialylation of Glycosides by Cells

The synthesis of sialylated glycosides using saccharide primers and cells was investigated. α · and β · Saccharide primers were chemically synthesized and introduced into B16 melanoma cells to prime oligosaccharide synthesis. Incorporation of α‐ and β‐dodecyl lactosides into B16 cells resulted in the sialylation of the galactose residue to give GM3‐type oligosaccharides. The β‐dodecyl galactoside primer was sialylated but the α‐dodecyl galactoside primer was not. Both the α‐ and β‐dodecyl glucoside primers were not elongated. In the glycosylation of primers by cells, this research confirmed that sialyl transferases tolerate acceptor modifications and are permissive to primer elongation regardless of the α‐ or β‐linkage to the aglycon unit. However, the presence of the terminal galactose residue that is β‐linked to the adjacent saccharide or aglycon unit is essential for sialylation by cellular enzymes to occur.     

Analysis of liquid structure without construction of any structure models by the X-ray scattering method.

A simple approach for determining a liquid structure using X-ray scattering data, in which a liquid structure is uniquely evaluated without construction of any plausible structure models, has been applied to liquid acetonitrile, acetone and cyclohexane. For a pair of molecules, a given point within a molecule is located at the origin with a given molecular orientation. The site of the given point of another molecule is defined by the polar coordinates and the molecular orientation is treated by three Eulerian angles. These parameters are optimized by a non-linear least-squares calculation applied to X-ray scattering data. The reliability of the method was examined by determining the liquid structure of polar acetonitrile and the obtained intermolecular interatomic distances are in good agreement with the previously reported values. The method was then successfully applied to the determination of the liquid structure of acetone and cyclohexane. Especially for nonpolar cyclohexane, the construction of a variety of plausible structural models is very difficult. It was revealed that acetone has an ordered liquid arrangement similar to that found in its crystal, although the intermolecular distances in liquid acetone are different from those in the crystal. On the other hand, the liquid structure of cyclohexane is disordered.     

Copolymerization of ethylene or propylene with α‐olefins containing hydroxyl groups with zirconocene/methylaluminoxane catalyst

Copolymerization of olefins (ethylene and propylene) and 5‐hexen‐1‐ol pretreated with alkylaluminum was performed using [dimethysilylbis(9‐fluorenyl)]zirconium dichloride/methylaluminoxane as the catalyst. The copolymerization required extra addition of alkylaluminum to prevent deactivation of the catalyst when 5‐hexen‐1‐ol was pretreated with trimethylaluminum, whereas the triisobutylaluminum‐treated system did not require any addition of alkylaluminum. The molecular weight of the copolymer depended on the kind of alkylaluminum compound (masking reagent, additive, and cocatalyst). ¹³C NMR analysis proved that poly(ethylene‐co‐5‐hexen‐1‐ol) containing 50 mol % of 5‐hexen‐1‐ol acted as an alternating copolymer, whereas the poly(propylene‐co‐5‐hexen‐1‐ol) acted as a random copolymer. The surface property of the copolymers was simply evaluated by means of water drop contact angle measurement. It was found that the copolymers containing large amounts of 5‐hexen‐1‐ol units showed good hydrophilic properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 52–58, 2004