Mamoru Soga

Novel organosynthetic routes to polythiophene and its derivatives

Abstract Polythiophene and its 3-alkyl derivatives have been synthesized by novel organosynthetic techniques. The organochemical syntheses were carried out by dehydrohalogenation of 2-halogenothiophene (or its 3-alkyl derivatives) or by dehydrogenation of thiophene (or its 3-alkyl derivatives). Copolymers can also be obtained from a solution involving two (or more) kinds of thiophene monomer species. The resulting polythiophene and its derivatives have well-defined chemical and electronic structure and molecular weights as large as 2.5 × 10 5 . The poly(3-alkylthiophenes) with long alkyl side groups, typically poly(3-hexylthiophene), are readily soluble in common organic solvents and can subsequently be processed into uniform films from their solution. These solution-cast films, furthermore, can be easily stretched up to a stretching ratio of about five. The stretched films exhibit excellent conductivity (as high as 200 S/cm) after doping. The effect of the copolymerization between two thiophene monomers is also discussed.

Development of a transparent and ultrahydrophobic glass plate

A transparent glass plate was roughened at the submicron level, and then a chemically adsorbed monolayer of a fluorocarbon compound was formed along the glass surface. The monolayer was prepared using the chemical coupling reaction accompanying dehydrochlorination between a chlorosilyl group of the heptadeca-fluorodecyltrichlorosilane (CF3(CF2)7(CH2)2SiCl3: HFTS) surface-active agent and a hydroxyl group on the glass surface. The contact angle of the glass surface relative to water was approximately 155 degrees with transmittance kept at 92%. This glass plate may be useful for various products, such as motor vehicles and building window glass.

13C NMR and Fourier transform infrared study of electrochemically prepared polythienylene film

Abstract The 13 C NMR and Fourier transform infrared (FTIR) spectra of an electrochemically prepared polythienylene film have been obtained. The polythienylene film displays only two sharp absorption bands, at 124.8 and 136.5 ppm downfield from TMS (tetramethylsilane) in the 13 C NMR, these being attributable to the carbon atoms in the β-position and the α-position, respectively, relative to the sulfur atom of poly(2,5-thienylene). The polythienylene film also shows a sharp absorption band at 789 cm −1 in the IR, which is definitely ascribable to the C-H out-of-plane vibration of poly(2,5-thienylene). The polythienylene film will be shown to have a highly defined structure with a dominance of poly(2,5-thienylene).

Electrochemically prepared poly(3-methylthienylene) films doped with iodine

Abstract Electrochemically prepared poly(3-methylthienylene) films doped with iodine have been investigated and the relationship between their conductivity and iodine content was studied. The conductivity of the films with various iodine contents was obtained in accordance with an Arrhenius equation with an activation energy equal to 0.17 to 0.033 eV. The highest conductivity was 5 S cm−1. The activation energy, which is dependent on the iodine content, shows discontinuous change, as is the case with polyacetylene doped with iodine. The relationship between conductivity and structure of the poly(3-methylthienylene) films will be discussed.

Applications of a Chemically Adsorbed Monomolecular Layer Having a Fluorocarbon Chain as an Anti-Contamination Film

Monomolecular layers having a fluorocarbon chain were developed and made suitable for practical use as anti-contamination films for glasses, such as front door window glass plates of automobiles and window glass plates of electric ovens or microwave ovens, and also for stainless steel applications, such as covers of electric rice cookers, by using a chemical adsorption technique for the first time in the world. The layer was anchored to the substrate surface through covalent bonds. Thus the layer did not peel off and was durable against rubbing and scratching. As the film thickness was from about 1 to 2 nm, the layer was also optically transparent and the luster and color tone of the substrates was maintained. The lowest surface tension obtained was 8.2 mN/m, which is about a half that of Teflon. Although thermo-durability was a little low in comparison with that of Teflon, the production cost was lower. Thus this anti-contamination film should be very useful in the field of anti-contamination surface treatment.

13C NMR spectrum analysis of electrochemically prepared poly(3-methylthienylene) films

Abstract The 13 C NMR spectrum analysis of electrochemically prepared poly(3-methylthienylene) films has been investigated. Both a film doped with ClO 4 ions (P3MT-ClO 4 ) and an undoped film (P3MT 0 ) give only two distinct absorption bands through the electrochemical reduction of P3MT-ClO 4 . These distinct bands are definitely attributable to the methyl group (upper field) and the thiophene ring (lower field), respectively, and are characteristic of well-defined poly(3-methylthienylene). The correlation between conductivity and 13 C NMR spectra will be discussed.

Contact angle and atomic force microscopy study of reactions of n-alkyltrichlorosilanes with Muscovite micas exposed to water vapor plasmas with various power densities

Monolayers of n-alkyltrichlorosilanes (CH3(CH2)n -1SiCl3: Cn) were formed on the surface of Muscovite micas after various numbers of reactive sites were formed on the mica surfaces by exposing the micas to water vapor plasmas whose power, P, varied from 0 to 100 W. Contact angle measurements of the monolayers showed that the coverages of Cn molecules at n8 on the mica surfaces increased with an increase in the plasma power on the micas. On the other hand, the coverages of Cn molecules at n>8 on the micas were not so sensitive to the plasma power as those at n8. The atomic force microscopy (AFM) observations of the growth process of the monolayers from C18 showed that island structures were formed on the mica surfaces at the low coverages of the monolayers and that each island grew and eventually came into contact with the other islands as the coverage increased. In contrast, island structures were not observed on the mica surfaces during the growth process of C4 monolayers. These results propose a reaction model of Cn molecules with micas, where Cn molecules at n>8 are hydrolyzed with adsorbed water on the micas in the Cn solutions, followed by condensing to form two-dimensional polymerized network domains; Cn molecules at n8 are hydrated with the adsorbed water on the micas in the Cn solutions, but the domain sizes of the two-dimensional polymerized network are not so large as those at n>8 because of a limitation of the condensation among the molecules.

New Method for Fabricating a Mixed Monolayer Using Self-assembly of Trichlorosilanes and Mapping of Different Molecules in the Mixed Monolayer Using a Frictional Force Microscopy with a Tip Chemically Modified with Fluoroalkyltrichlorosilanes for Chemical Sensing

An alkyltrichlorosilane/fluoroalkyltrichlorosilane mixed monolayer was fabricated by the self-assembly of an octadecyltrichlorosilane (OTS) monolayer having pinholes with 10–200 nm radii and following adsorption of (2-(perfluorooctyl)ethyl)trichlorosilane (FS-17) into the pinholes. The adsorption of FS-17 into the pinholes was confirmed using an atomic force microscope (AFM) by measuring the hole depths in the OTS monolayer, which decreased by a molecular length of FS-17 after the adsorption of the FS-17. The OTS and FS-17 molecules in the mixed monolayer were mapped using a frictional force microscope (FFM) whose tip was chemically modified with FS-17 molecules. In the case of the conventional observation using a FFM whose tip is not chemically modified, the frictional forces of the tip on the FS-17 molecules in the pinholes were smaller than those on the OTS monolayer. In contrast, the frictional forces of the chemically modified tip on FS-17 molecules in the pinholes were larger than those on the OTS monolayer. These results indicate that the FS-17 molecules on the tip have a critical influence on the frictional force between the tip and the molecules, and that the chemically modified tip may be used for discriminating different chemical groups in the monolayer. We propose that our new techniques for fabricating and estimating molecular distributions of the mixed monolayer will be useful in the development of molecular electronic devices.

Preparation of fluorocarbon multilayers by a chemical adsorption technique

Preparing fluorocarbon multilayers by chemical adsorption or self-assembly was investigated. 1,10-Bis (trichlorosilyl) dodecafluorodecane (bis-trichlorosilane) was chemically adsorbed on aluminum coated glass plates in nonaqueous solution. The plates were washed with chloroform and deionized water, and then dried. The electrical properties of the multilayers, such as capacitance, tan δ, leak current, and breakdown voltage were evaluated. The capacitance measurements imply that the multilayers of the bis-trichlorosilane molecules can be formed by repeating the chemical adsorption process.

Preparation of a Polyacetylene Derivative Monolayer for Molecular Wire

A polyacetylene derivative monolayer was investigated for application as a molecular wire. First, an acetylene derivative monolayer was prepared by chemically adsorbing (self-assembling) 19-trimethylsilyl-18-nonadecynyl- trichlorosilane on a silica substrate. Then, the monolayer was polymerized in the presence of Ziegler-Natta catalyst of triethyl aluminum and tetra-n-butoxy titanium. The polyacetylene derivative monolayer thus synthesized was covalently bonded to the silica substrate and showed conductivity as high as 1×10-4 S/cm after being doped with iodine. The method of preparing a conductive polymer monolayer by combination of chemical adsorption and catalytic polymerization leads to a molecular wire which is one of the key technologies for molecular devices.