Efficient Transformation of Polymer Main Chain Catalyzed by Macrocycle Metal Complexes via Pseudorotaxane Intermediate

Post-synthesis modification of polymers streamlines the synthesis of functionalized polymers, but is often incomplete due to the negative polymer effects. Developing efficient polymer reactions in artificial systems thus represents a long-standing objective in the fields of polymer and material science. Here, we show unprecedented macrocycle-metal-complex-catalyzed systems for efficient polymer reaction that result in 100 % transformation of the main chain functional groups presumably via a processive mode reaction. The complete polymer reactions were confirmed in not only intramolecular reaction (hydroamination) but also intermolecular reaction (hydrosilylation) by using Pd- and Pt-macrocycle-catalyzed systems. The most fascinating feature of the both reactions is that higher-molecular-weight polymers reach completion faster. Various studies suggested that the reactions occur in the catalyst cavity via the formation of a supramolecular complex between the macrocycle catalyst and polymer substrate like pseudorotaxane, which should be of characteristic of the efficient polymer reactions progressing in a processive mode.     

Synthesis of bi-fluorescence-labeled lactoside: A substrate for continual assay of ceramide glycanase

A bi-fluorescence labeled derivative suitable for analysis of ceramide glycanase activity was constructed from 4-pentenyl lactoside. Selective modification of the galactosyl residue was attained by formation of 4′,6′-naphthylmethylidene derivative, which was followed by regioselective reductive ring opening. The aglycon was extended by Michael addition of 2-aminoethanetiol, and dansylated at the terminal amino group. Excitation of the naphthyl group results in emission from the dansyl group, while the emission from the naphthyl group is quenched by the dansyl group. Upon digestion with ceramide glycanase, the energy transfer is severed and a decrease in the dansyl emission concommitant with an increase in the naphthyl emission was observed. This substrate was successfully used to analyze ceramide glycanase activity.     

Fluorescence study of polyelectrolyte complex formation III: Mobility of probes in microdomains

The mobility of fluorescent probe molecules in the microdomains formed by polyelectrolyte complexes (PEC) in aqueous solution was investigated by the fluorescence polarization method. The degree of fluorescence polarization (p) for the anthracene (Anth) chromophores attached to anionic polyelectrolytes increased with complexation, indicating the restricted mobility of probe molecules in the PEC microdomains. These p values depended on the properties of added polycations, which were not in parallel with the fluorescence intensities of the Anth chromophores.     

HRTEM study of new superconducting lead cuprate (Pb, Cu) (Eu, Ce)2(Eu, Sr)2Cu2Oz

Crystallographic properties of a new lead cuprate superconducting material (Pb, Cu) (Eu, Ce)₂(Eu, Sr)₂Cu₂O_z are examined by electron probe micro-analysis and transmission electron microscopy. It is confirmed that although the sample examined here is not of single-phase, the composition of the superconducting phase is close to the nominal composition. From TEM observations, it follows that the crystal structure of the new phase is similar to that of Tl-1222 which consists of a fluorite type block, a rock salt type layer and a perovskite block.     

Conductance of Electrolytes in Wet Pulp Webs

The electric conductivity of wet pulp webs was measured at various water contents, after the water was replaced with KCl solutions of various concentrations. A specific KCl concentration in the wet pulp web equivalent to the total amount of electrolytes and dissociative groups that existed originally in the wet pulp fibers was determined from the linear relationship between the electric conductivity and the concentration of KCl added. Molar conductivity of the KCl in the wet pulp web is lower than that of the KCl solution. The amount of nonconductive water (W_non) was estimated from the difference in molar conductivity between the wet pulp web and the KCl solution. W_non is a kind of bound water and increases with degree of beating of the pulp.     

Optical Computed Tomography Imaging of Absorbers in a Highly Scattering Medium by Detection of Photons Preserving Initial Polarization

A method utilizing light polarization was applied to take the projection data of absorbers in a highly scattering medium. The floor level of the projection data due to diffused light was significantly suppressed by detection of photons which preserved initial polarization. An optical computed tomgraphy image was reconstructed from the projection data taken by this method and exhibited higher spatial resolution than the image reconstructed from the projection data by conventional method.