Reference standards for negative ion mass spectrometry

The negative ion mass spectra of phosphonitrile chlorides (PNCl₂)_n (n≥3) are studied. Since this series of compounds give very intense negative [M]^? and [M? Cl]^? ions, they can be used as good reference standards for negative ion mass spectrometry.     

Nanostructure of a "carpet"-like dense layer/polyelectrolyte brush layer in a block copolymer monolayer at the air-water interface

The "carpet"/brush double layer structure in the polyelectrolyte layer in the amphiphilic diblock copolymer monolayer at the air-water interface was quantitatively studied by in situ neutron reflectometry in addition to X-ray reflectivity measurements. As a result of the higher contrast between polyelectrolyte [poly(methacrylic acid)] and solvent (D(2)O) for the neutron, the brush structure could be estimated more accurately as a function of surface pressure, that is, brush density. The thickness of the carpet layer, which is thought to be formed to reduce the interfacial free energy between water and the hydrophobic layer, was almost constant at 10-20 A at any surface pressure studied. Growth was clearly observed in the whole brush length with increasing surface pressure, and it was estimated to be almost 60% of the full-stretch length of the ionic polymer chain. Furthermore, by the comparison of density profiles by neutron and X-ray reflectometry, an anomalous hydration was suggested.     

Water adsorption on Rh(111) at 20 K: from monomer to bulk amorphous ice

The adsorption of water (D(2)O) molecules on Rh(111) at 20 K was investigated using infrared reflection absorption spectroscopy (IRAS). At the initial stage of adsorption, water molecules exist as monomers on Rh(111). With increasing water coverage, monomers aggregate into dimers, larger clusters (n = 3-6), and two-dimensional (2D) islands. Further exposure of water molecules leads to the formation of three-dimensional (3D) water islands and finally to a bulk amorphous ice layer. Upon heating, the monomer and dimer species thermally migrate on the surface and aggregate to form larger clusters and 2D islands. Based on the temperature dependence of OD stretching peaks, we succeeded in distinguishing water molecules inside 2D islands from those at the edge of 2D islands. From the comparison with the previous vibrational spectra of water clusters on other metal surfaces, we conclude that the number of water molecules at the edge of 2D islands is comparable with that of water molecules inside 2D islands on the Rh(111) surface at 20 K. This indicates that the surface migration of water molecules on Rh(111) is hindered as compared with the cases on Pt(111) and Ni(111) and thus the size of 2D islands on Rh(111) is relatively small.     

Association behavior of fluorine-containing and non-fluorine-containing methacrylate-based amphiphilic diblock copolymer in aqueous media

Fluorine-containing amphiphilic block copolymers, poly(sodium methacrylate)-block-poly(nonafluorohexyl methacrylate) (NaMAm-b-NFHMAn) (m:n = 61:12, 72:33, 64:57), and the corresponding non-fluorine-containing amphiphilic block copolymer, poly(sodium methacrylate)-block-poly(hexyl methacrylate) (NaMAm-b-HMAn) (m:n = 64:10, 69:37, 67:50), were synthesized. Both polyNaMA-b-polyNFHMA and polyNaMA-b-polyHMA formed micelles above critical micelle concentrations, (cmc's), around 3 x 10(-5) to 1 x 10(-4) mol/L, while neither polymer decreased surface tension of aqueous solutions. The size and shape of the micelles were examined by dynamic light scattering, small-angle neutron scattering, and small-angle X-ray scattering. PolyNaMA-b-polyHMA appeared to form only spherical micelles, while polyNaMA-b-polyNFHMA with a long NFHMA segment formed both spherical and rodlike micelles. The micelles of fluorine-containing block copolymers were obviously larger than those of non-fluorine-containing block copolymers with the same chain length and the same hydrophilic/hydrophobic chain ratio. The fluorine-containing block copolymer selectively solubilized fluorinated dye into the water phase when a mixture of decafluorobiphenyl and 2,6-dimethylnaphthalene was added to the micelle solution.     

Electron spin resonance study of poly-3,3-bis(chloromethyl) oxetane irradiated with electron beams and ultraviolet light

Poly-3,3-bis(chloromethyl)oxetane (poly-BCMO) was irradiated at ?196°C with electron beams and ultraviolet light, and observed ESR spectra were compared. A three-line spectrum (coupling constant of about 21 gauss) and a two-line spectrum (coupling constant of about 18 gauss) were observed after irradiation with electron beams in vacuo. They were attributed to free radicals and respectively. On the other hand, a three-line spectrum (coupling constant of about 20 gauss) and an asymmetric singlet spectrum were observed after ultraviolet irradiation in vacuum. They were assigned to free radicals and ? CH₂? O·, respectively. Mechanisms of radical formation were discussed in each case. When poly-BCMO was irradiated with electron beams at ?196°C in the presence of air, peroxy radicals were produced after subsequent treatment at ?78°C. The reaction between alkyl radicals and oxygen molecules was found to be diffusion-controlled.     

Multimetalated carboxylates in a filament in-beam electron impact mass spectrometer

An in-beam electron impact mass spectrometer has been modified using a tungsten or platinum filament as an in-beam probe. With this simple device, metalated organic molecular ion peaks of strong intensities are observed under electron impact conditions. New cluster ions, [(CH₃CO₂)_mLi_n]⁺ are detected, where m=3-6 and n=3, 4. Sodium and potassium acetates give stable dimetalated carboxylate ions, and less stable carboxylate ions are formed from benzoates.     

Synthesis of biotinylated sialoside to probe CD22-ligand interactions

Biotin conjugate of the most potent ligand for mouse CD22 was designed and synthesized. The key synthetic step involved the dual capability of Hanessian reaction for debenzylation and simultaneous conversion of the anomeric p-methoxyphenyl group into the corresponding phenylthioglycoside in one step. Competition enzyme-linked immunosorbent assay (ELISA) for testing the binding affinity of synthetic sialosides was developed based on this biotinylated ligand.