Quantitative evaluation of interfacial adhesion between fiber and resin in carbon fiber/epoxy composite cured by semiconductor microwave device

Interfacial adhesion between carbon fiber (CF) and epoxy resin in carbon fiber-reinforced epoxy composite, which was prepared by different heating process such as semiconductor microwave (MW) device and conventional electric oven, has been evaluated quantitatively. The interfacial shear strength (IFSS) between CF and epoxy resin, which was an indicator of adhesion on the interface, was measured by a single fiber fragmentation test. The single fiber fragmentation test showed that the IFSSs of the prepared specimens were different by heating methods. In the case of MW process, the curing reaction of epoxy resin on the CF interface would be progressed preferentially due to the selective heating of CF, resulting that the IFSSs of specimens prepared by MW irradiation were increased by enhancing the output power of MW. However, the IFSSs of the specimens were decreased by excessively high output power because the matrix resin on the CF interface was thermally degraded. As results, by optimizing the MW conditions of output power and irradiation time, the IFSS of the sample cured by MW was increased by 21% as compared to oven-heated one. It was found that the interfacial adhesion between CF and epoxy resin would be improved by the MW-assisted curing reaction on the surface of CF.     

Ultra-fast One-Handed Helix Induction and Its Static Helicity Memory in a Poly(biphenylylacetylene) with a Catalytic Amount of Chiral Ammonium Salts

We report an ultra-fast helix induction and subsequent static helicity memory in poly(biphenylylacetylene) (PBPA- A ) assisted by a catalytic amount of nonracemic ammonium salts comprised of non-coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF⁻) as a counter anion. The remarkable acceleration of the helix-induction rate in PBPA- A accompanied by the significant amplification of the asymmetry relies on the two methoxymethoxy groups of the biphenyl pendants, which can gain access to enfold the chiral ammoniums in a crown-ether manner in specific aromatic solvents, leading to ultra-fast helicity induction, which is completed within 30 s. In aromatic solvents, helicity memory is lost rapidly, but is quite stable in long-chain hydrocarbons. The best use of specific solvents for helicity induction and static helicity memory, respectively, provides a highly sensitive chirality sensing system toward a small amount of chiral amines and amino acids when complexed with BArF⁻.     

Development of In Situ Electrochemical Scanning Electron Microscopy with Ionic Liquids as Electrolytes

We report that ionic liquids (ILs) can be observed by electron microscopy without any charging of the liquid. Based on this, we present an in situ electrochemical scanning electron microscopy (in situ ECSEM) system. The key technology that enables in situ ECSEM is that charges can be removed from an IL by grounding it with a Pt wire, even if the IL is in an insulating glass cell. As a first demonstration, we describe the redox reaction of a polypyrrole (PPy) film accompanied by changes in its thickness when it is polarized by the film‐deposited Pt electrode in the IL. Furthermore, energy‐dispersive X‐ray fluorescence (EDX) analysis can be employed for the electrode polarized in the IL. The component analysis by EDX of PPy in an IL containing K⁺ as a marker, reveals doping of electrolyte cations into the PPy film upon the latter′s reduction and dedoping of cations from the film upon oxidation.     

Synthesis of CH2-linked alpha(2,3)sialylgalactose analogue: on the stereoselectivity of the key Ireland-Claisen rearrangement

A CH 2 -linked alpha(2,3)sialylgalactose analogue was efficiently synthesized using an Ireland-Claisen rearrangement, which was developed recently by our group for constructing a CF 2 -sialoside. The reaction conditions of the rearrangement were optimized for alpha-stereoselective formation of the CH 2 -sialoside. On the basis of the observed temperature effects, the origin of the stereoselectivity of the Ireland-Claisen rearrangement is discussed. Moreover, reconstruction of the 2alpha-hydroxyl group on the galactose unit of the rearrangement product was achieved by means of stereoselective dihydroxylation and deoxygenation.     

A new H2O2/acid anhydride system for the iodoarene-catalyzed C-C bond-forming reactions of phenols

We have succeeded in the first versatile iodoarene-catalyzed C-C bond-forming reactions by development of a new reoxidation system at low temperatures using stoichiometric bis(trifluoroacetyl) peroxide A in 2,2,2-trifluoroethanol (TFE). The catalytic system supplies a wide range of substrates and functional availabilities sufficient to be used in the key synthetic process of producing biologically important Amaryllidaceae alkaloids.     

Carbonylative Polymerization of Oxetanes Initiated by Acetyl Cobalt Complexes

Four acetyl cobalt complexes, [AcCo(CO)₃P(p‐tolyl)₃] ( 1 ; p‐tolyl=4‐Me‐C₆H₄), [AcCo(CO)₃P(OPh)₃] ( 2 ), [AcCo(CO)₃P(NMe₂)₃] ( 3 ), and [AcCo(CO)₂(dppp)] ( 4 ; dppp=1,3‐bis(diphenylphosphanyl)propane), were synthesized, characterized, and examined as catalysts for the unprecedented carbonylative polymerization of oxetanes. Copolymers containing ester (4‐hydroxyalkanoate) and/or ether units were obtained with complexes 1 and 2 , but not with complexes 3 and 4 either in the presence or absence of additional phosphorus ligands. The ester unit/ether unit ratio varied in the range 21:79–63:37, and the highest ester/ether ratio of 63:37 was achieved by using complex 1 in the presence of a further 5 equivalents of P(OPh)₃. Although direct carbonylative polymerization is possible, preformation and ring opening of the γ‐lactone is also suggested as an alternative pathway.