Mitsuyasu Kawahara

Synthesis and proton conductivity of thermally stable polymer electrolyte: poly(benzimidazole) complexes with strong acid molecules

Abstract We synthesized thermally stable proton-conducting polymers composed of poly(benzimidazole) (PBI) and strong acids. PBI films were doped with strong acids such as phosphoric, sulfuric, and hydrochloric acid by immersing them into a mixed solution of strong acid and methanol. We found that the PBI films and strong acids formed polymer complexes because they showed the acid–base or the hydrogen bonding interactions between imidazole groups of PBI and acid molecules. The PBI/H 3 PO 4 complexes were thermally stable up to 500°C, and the proton conductivity of anhydrous complexes reached 10 −5 S cm −1 at 160°C.

Relationship between absorbed water and proton conductivity in sulfopropylated poly(benzimidazole)

A novel proton-conducting polymer, sulfopropylated poly(benzimidazole) (PBI-PS), was synthesized by the ring-opening reaction of 1,3-propanesultone on the reactive N-H groups of PBI. Cast films of PBI-PS obtained from a dimethylsulfoxide solution of PBI-PS exhibited high water uptake, adequate mechanical strength, and flexibility. The temperature dependence of proton conductivity for PBI-PS films hydrated at 90% R.H. showed high proton conductivity of the order of 10−3 Scm−1 in the temperature range from room temperature to 140 °C, which is superior to those of conventional proton conducting polymers such as Nafion. The physical behavior of absorbed water in hydrous PBI-PS films was evaluated by differential scanning calorimetry (DSC), indicating that the absorbed water in PBI-PS mainly consisted of freezing bound water. Copyright

Ion conductivity of poly(ethylene oxide)/ligand complexes with the hydrogen-bond interaction

Abstract New polymer/ligand complexes could be easily obtained due to the molecular self-assembly of carboxylic acid and hydrogen acceptor fragments through the intermolecular hydrogen-bonding. The polymer/ligand complexes consisting of poly(ethyleneglycol)bis(carboxymethyl)ether (PEOCA), operating as a hydrogen-bonding donor, and pyrazine, 4,4′-bipyridine, or 1,3,5-triazine, serving as a hydrogen-bonding acceptor, exhibited a gel-like structure at room temperature. The high ion conductivity of the order of 10−4–10−6 S cm−1 was achieved for the PEOCA/ligand complexes with LiClO4. The decrease in their conductivity corresponded to the increase in the viscosity and glass transition temperatures of the polymer complexes, but their electrical properties were similar to those of conventional cross-linked PEO polymer electrolytes.

Novel Organic-Inorganic Hybrid Compounds Containing Alkyldiammonium Salts

Novel organic-inorganic hybrid compounds, C n N 2 PbBr 4 (n=4,6,8 and 10) and C 2 N 2 PbBr 4 · DMSO, were prepared by the self-organization of lead bromide and a variety of alkyldiammonium cations. The powder X-ray diffraction patterns of C n N 2 PbBr 4 demonstrated that the compounds form layered perovskite structures and the interlayer spacing are dependent on the length of alkyl chain. The absorption and fluorescence spectra of C n N 2 PbBr 4 and C 2 N 2 PbBr 4 · DMSO crystalline powder showed an excitonic absorption peak at around 390 nm, which suggests that the formation of two-dimensional inorganic sheets and quantum confinement structure.

Crystal Structure and Optical Properties of C 10 H 10 N 2 PbBr 4 and C 10 H 22 N 2 PbBr 4

Novel organic-inorganic hybrid compounds, C 10 H 10 N 2 PbBr 4 and C 10 H 22 N 2 PbBr 4 were prepared and characterized by X-ray and optical measurements. The result of single crystal X-ray analysis showed that the inorganic region of C 10 H 10 N 2 PbBr 4 consisted of one-dimensional chains of line-sharing PbBr 6 octahedra, whereas that of C 10 H 22 N 2 PbBr 4 consisted of two-dimensional sheets of corner-sharing PbBr 6 octahedra. Each crystal exhibited an excitonic band at 307 nm for C 10 H 10 N 2 PbBr 4 and 383 nm for C 10 H 22 N 2 PbBr 4 , which is attributed to the excitonic states of low-dimensional inorganic structures. These results indicate that the dimensional structure of these compounds can be systematically controlled by changing the chemical structure of organic ligands.