Platinum Nanosheets between Graphite Layers

Two‐dimensional platinum nanosheets were obtained by the hydrogen reduction of platinum tetrachloride intercalated between graphite layers, the latter was prepared by the treatment of the mixture of platinum tetrachloride and graphite powder under chlorine atmosphere. The size of platinum nanosheets was 1–3 nm in thickness with a width in the range of 5–300 nm. These nanosheets contain a number of hexagonal holes and edges with an angle of 120°. This review discusses the reduction and oxidation behavior of platinum species and structure of platinum nanosheets between graphite layers. The selective hydrogenation catalyzed by these platinum nanosheets entrapped between the graphite layers is also demonstrated.     

Synthesis,characterization, and physical properties of new copolymers of poly(amino acid)–urethane—copolymers of γ‐methyl‐L‐glutamate‐N‐carboxyanhydride and urethane prepolymer

New copolymers of amino acid and urethane (PAU), in which a polyurethane segment was combined with poly(γ‐methyl‐L‐glutamate) (PMLG) of various contents, were synthesized by the copolymerization of the polyurethane prepolymer (UPP) having isocyanate groups at both terminals of the chain and γ‐methyl‐L ‐glutamate‐N‐carboxyanhydride (NCA) to improve the elastic recovery and adhesion of PMLG for application of PMLG to synthetic leather. The copolymerization of the UPP with NCA was carried out by applying the reactivity of isocyanate and the polymerization mechanism of NCA using the primary amine and tertiary amine as initiators. Infrared (IR) and ¹³C‐NMR spectra of these PAUs as well as the chemical analysis of the PAU intermediates showed that the PAUs would have a multiblock–triblock structure: namely, the PAUs consisted of the block copolymer segments of urethane and a small amount of PMLG at the center of the copolymer chain and most of the PMLG at both terminals of the copolymer chain. The elastic recovery and adhesion of these PAUs were significantly larger than those of the PMLG with the maintenance of a good sense of touch, which was a unique asset of PMLG. Furthermore, it was found that the PAUs had intermediary moisture permeability between that of PMLG and polyurethane. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 383–389, 1999     

Polycondensation of Terephthalic Acid and 3,3′‐Dimethyl Bisphenol A with TsCl/DMF/Py in the Presence of Salts

When activated with TsCl/dimethylformamide/pyridine in the presence of lithium, ammonium, or phosphonium salts, activated terephthalic acid of difficult solubility in pyridine became soluble. Depending on the kind and amount of the salt, terephthalic acid reacted smoothly with 3,3′‐dimethyl bisphenol A to yield the corresponding polymer having high molecular weight. However, this reaction could not be successfully applied to the preparation of polyesters from other dicarboxylic acids of difficult solubility.     

Molecular orientation of paramagnetic metal complex by melt-drawing thermotropic liquid crystalline polymers

New liquid-crystalline polyesters and paramagnetic vanadyl complex were prepared as host polymer and guest complex. Melt-drawn fibers were made from the blend of host polymer and guest complex at the mesophase temperature. ESR spectra of the melt-drawn fibers indicated that the base of pyramidal vanadyl complex is completely oriented parallel to the fiber axis.