The intercalation reaction of aniline and alkylanilines into α-tin (IV) bis (hydrogenphosphate) (α-SnP) was conducted by mixing α-SnP and benzene solutions of the amines at 25°C for 4 days, where the amine/α-SnP molar ratio (r) was varied. Aniline was intercalated into α-SnP at r of 17.1 or higher, and its interlayer distance spreaded. In the case of toluidine and ethylaniline at r of 34.1, nitrogen/phosphorus (N/P) molar ratio and interlayer distaces of the products varied for a kind of isomers of guest molecule. That is to say, m-and p-isomers of toluidine and ethylaniline were intercalated and interlayer distance of α-SnP spreaded, whereas the corresponding o-isomers were not. The numbers of p-isomers intercalated were larger than those of m-isomers. It is considered that the steric hindrance of alkyl groups for bonding of amino groups with P-OH of α-SnP, and the differences of basicity of each isomer gave dependence of intercalation behavior of toluidine and ethylaniline into α-SnP on their isomers. In the case of intercalation of p-alkylanilines at r of 34.1, the N/P molar ratio of products decreased with increasing the number of carbon atoms in their alkyl chains. These amine molecules form a bilayer in the interlayer space of α-SnP, and their alkyl chains are inclined to the α-SnP layer by ca. 81°.

View full abstract

Ionically conductive thin films are prepared by utilizing a plasma polymerization technology. Sulfonic acid group is introduced into plasma polymer by designing starting monomers and controlling plasma conditions such as applied electric power of RF, monomer flow rate, and polymerization pressure. The produced films of thickness up to a few um adhere tightly on different kinds of substrates and are uniform and free from pinhole. Methyl benzenesulfonate and benzenesulfonyl fluoride are useful to introduce sulfonic acid group. To prepare ion-exchange films of hydrocarbon type the reaction pressure of 20-100 Pa and applied power of 10-30 W are adequate. A gaseous mixture of trifluoromethane sulfonic acid and hexafluoropropylene gives a perfluorinated cation-exchange thin film under the limited plasma conditions. The produced film is highly cross-linked leading to low water uptake and hence its ionic conductivity is low, while its ion-exchange is fairly high and comparable to that of Nafion.

View full abstract

There are many types of manganese oxides with tunnel and layered structures. We reviewed the preparation methods, metal ion extraction/insertion reactions, and ion-sieve properties of manganese oxide ion-sieves with tunnel and layered structures, mainly on the basis of our recent studies. The metal ion extraction/insertion reactions with the manganese oxide ion-sieves progress by two different reactions: redox-type and ion-exchange-type. The selective adsorptive sites for the metal ions can be classified into redox-type and ion-exchange-type.
The adsorptive selectivities for metal ions are dependent on the structures of the manganese oxide ion-sieves. Spinel-type, hollandite-type, and birnessite-type manganese oxide ion-sieves show specific selectivities for the adsorptions of Li⁺, K⁺, and Rb+ ions, respectively. The sizes of these ions correspond to the sizes of tunnels or interlayer space of the ion-sieves. The effective pore radii of the spinel-type, hollandite-type, birnessite-type, and todorokite-type manganese oxide ion-sieves are estimated as 0.7, 1.4, 1.5, and 2.7Å, respectively.
A hydrothermal soft chemical process, novel process for the preparation of ion-sieves, is suitable to obtain various kinds of manganese oxides with tunnel structures.

View full abstract

The authors' works on adsorption behavior for metal ions of chitosan which is one of the most abundant biomass resources on the earth is reviewed. It was stressed from the experimental results of the effects of pH and crosslinking on the adsorption and of the adsorption isotherms of copper (II) that chitosan exhibits interesting and excellent adsorption behavior with high selectivity and loading capacity much superior to commercial chelating resins. The driving force resulting in such excellent adsorption behaviors was discussed.

View full abstract