Fracture mechanism of liquid‐crystalline epoxy resin systems with different phase structures

A liquid‐crystalline epoxy resin was cured at two different temperatures. The phases of the cured systems clearly showed isotropic and nematic polydomain structures, which depended on the curing temperature. The fracture toughness of the systems was measured, and the fracture mechanism was investigated with polarized IR measurements. The nematic polydomain structure system showed considerably higher fracture toughness than the isotropic structure. Moreover, both systems exhibited a reorientation of the network chains near the fracture surface during the fracture process, and the region of the network reorientation in the nematic polydomain structure system was larger than that in the isotropic structure system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4044–4052, 2004     

Synthesis of 3-hydroxyindolin-2-one alkaloids, (±)-donaxaridine and (±)-convolutamydines A and E, through enolization-Claisen rearrangement of 2-allyloxyindolin-3-ones

Claisen rearrangement triggered by enolization of 2-allyloxyindolin-3-ones with DBU was performed in order to prepare 3-allyl-3-hydroxyindolin-2-ones. Total synthesis of 3-hydroxyindolin-2-one alkaloids, (±)-donaxaridine, as well as (±)-convolutamydines A and E, was achieved by transformation of the allyl moiety of 3-allyl-3-hydroxyindolin-2-ones.     

Influence of the network chain orientation on the fracture toughness of a mesogenic epoxy resin modified with CTBN

A biphenol‐type epoxy resin, which had a mesogenic group in the backbone moiety, was modified with carboxy‐terminated butadiene acrylonitrile copolymer (CTBN) as a reactive elastomer, and its fracture toughness was measured. With the addition of CTBN, the fracture toughness of the biphenol‐type epoxy resin significantly increased and became significantly higher than that of a bisphenol A‐type epoxy resin modified with CTBN. The network chain orientation in the cured biphenol‐type epoxy resin system was clearly observed during the fracture process with polarized microscopy Fourier transform infrared measurements, although such a phenomenon was not observed in the bisphenol A‐type epoxy resin system. The high toughness of the cured biphenol‐type system was clearly due to the consumption of the mechanical energy by a large deformation of the matrix resin due to the orientation of the network chains during the fracture process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1198–1209, 2003     

Precise synthesis of porphyrin array scaffolding polyisocyanides

Aryl isocyanides bearing free‐base and metallo‐porphyrins were prepared and polymerized with a Pd–Pt μ‐ethynediyl complex as the initiator to give polymers with narrow polydispersity indices. The molecular weights of the resulting polymers were precisely controlled by the initial feed ratio of the porphyrin monomer to the initiator. The UV–VIS spectra suggested that the porphyrin pendants are regularly arranged to form stacked columns. Metallo‐porphyrin polymers were also prepared by reacting free‐base porphyrin polymers with metal salts. The successive reactions of free‐base and zinc‐porphyrin monomers resulted in the formation of diblock polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 585–595, 2006     

Thermal properties and fracture toughness of a liquid‐crystalline epoxy resin cured with an aromatic diamine crosslinker having a mesogenic group

A mesogenic‐type curing agent was synthesized to introduce a mesogenic group not only into epoxy resin backbones but also into the crosslink units. In the mesogenic curing agent system, the domain size became larger, and the network arrangement in each domain existed to a greater extent than that in a system cured with the ordinary diamine curing system according to the evidence from polarized optical micrographs and polarized Fourier transform infrared mapping measurements. Moreover, the fracture toughness of the system was considerably improved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2486–2494, 2006     

Über die Konzentrationsabhängigkeit der Viskosität bei organischen Hochpolymeren

Zusammenfassung Es wird eine Korrekturformel zur 8. Potenzformel von Philippoff-Heß vorgeschlagen, die auch die Fälle gut wiedergibt, wo die einfache 8. Potenzformel ebenso wie andere Viskositätsgleichungen bisher versagten. Im einzelnen wird die Gleichung geprüft an folgenden bisherigen Ausnahmen: Cellit in Eisessig (Philippoff-Heß), polymere-Hydroxydekansäuren in sym-Tetrachloräthan(Kraemer-von Natta), polymere Polystyrole in Benzol (Dane). In jedem Falle stellen diek-Werte gute Konstanten dar.Die charakteristische Viskositätskonstantek zeigt eine lineare Zunahme mit dem Molekulargewicht der Polymerhomologen.Die Temperaturabhängigkeit vonk unda wird geprüft.     

Quantitative estimation of interaction between carbohydrates and concanavalin A by surface plasmon resonance biosensor

We measured the affinity of more than 20 sugars with concanavalin A (ConA) by an optical biosensor (surface plasmon resonance sensor) using asialofetuin (ASF) as an immobilized binding partner of ConA. We determined kinetic parameters of the effects of sugars on the dissociation of ConA from ASF quantitatively, and the structural requirements of the functional groups of sugars for binding with ConA. We found that the affinity of ConA for sugars is dependent on its conformation induced by interaction with the binding partner. In addition, the results showed that optical biosensor system is well mimics the interaction of ConA with sugars in biomembrane.     

Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate

An overoxidized polypyrrole colloid, which can recognise enantiomers of amino acids has been prepared by a newly developed molecular imprinting technique. A polypyrrole colloid, which had been polymerised from a mixture of pyrrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and L-lactate (dopant), was overoxidized to create a dopant-complementary cavity. The enantioselectivity of the overoxidized colloid was evaluated by comparing the uptake of L-alanine and L-cysteine with that of the respective D-enantiomers. The L/D uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantiomers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by L-lactate. In contrast, a colloid templated with L-phenyllactate took up L-phenylalanine with a higher enantioselectivity of about 7. A colloid templated with L-lactate was applied to surface chirality analysis through enantioselective adsorption on cysteine-modified gold surfaces. Quartz microbalance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surface modified with L-cysteine than to one modified with D-cysteine.     

Synthesis, crystal structure and thermoelectric properties of a new carbide Zr2[Al3.56Si0.44]C5

A new quaternary layered carbide, Zr₂[Al_3.56Si_0.44]C₅, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and thermopower and electrical conductivity measurements. The crystal structure was successfully determined using direct methods, and further refined by the Rietveld method. The crystal is trigonal (space group R3m, Z=3) with lattice dimensions of a=0.331059(5), c=4.09450(5) nm and V=0.38864(1) nm³. The final reliability indices calculated from the Rietveld refinement were R_wp=6.24%, R_p=4.21% and R_B=0.82%. The crystal structure is composed of electroconductive NaCl-type ZrC slabs separated by Al₄C₃-type [Al_3.56Si_0.44]C₃ layers. This material had thermoelectric properties superior to those of the ternary layered carbides Zr₂Al₃C₄ and Zr₃Al₃C₅, with the power factor reaching 7.6×10⁻⁵W m⁻¹ K⁻².