Takashi Fukuda

IR and ram-an studies in three polyanilines with different oxidation levels

Summary form only given. FT-IR and non-resonance FT-Raman spectra have been measured in three kinds of polyanilines (PANIs) chemically synthesized, i.e., leucoemeraldine base (LB), emeraldine base (EB) and pernigraniline base (PB) with different oxidation levels. In Raman spectra shown in Fig. 1, the peaks at about 1600 cm/sup -1/ and 1176 cm/sup -/ are attributed to benzenoid unit (B), while the peak at 1380 cm/sup -1/ are to benzenoid unit (Q). In IR spectra, we also observed several characteristic peaks in three PANIs, which are attributed to N-H stretching (3380 cm/sup -1/), C=C and C-C streching and bending modes (B : 1600, 1500, 1150 cm/sup -1/, Q : 1380, 1300 cm/sup -1/). The variations of oscillator strength at each IR and Raman peak among three PANIs are consistently interpreted in the viewpoint of the ratio of benzenoid and quinoid moieties.

POLYQUINOXALINE AS AN EXCELLENT ELECTRON INJECTING MATERIAL FOR ELECTROLUMINESCENT DEVICE

Electron injecting properties have been studied for one of polyquinoxaline (PQx) derivatives. PQx was clarified to be an excellent electron injecting material for electroluminescent (EL) device because it has many advantageous properties such as high electron affinity, good thermal stability, good processability, and sufficiently low refractive index. On the other hand, since poly(p‐phenylenevinylene) (PPV) was known as a good hole injecting material, an EL device with ITO/PPV/PQx/metal type structure was suggested. It was shown that the quantum efficiency of the cell was higher than that of ITO/PPV/metal cell. Related physical and optical properties of PQx derivatives are also investigated.

Polyquinoxaline as an electron injecting material for electroluminescent device

Abstract A series of 2,3-disubstituted poly(quinoxaline-5,8-diyl) (PQx) was clarified to be an excellent electron injecting material for electroluminescent (EL) devices, since these have many advantageous properties such as high electron affinity (Ea:3.3 ~ 3.4 eV), good thermal stability, good processability and sufficiently low refractive index. On the other hand, since poly( p -phenylenevinylene) (PPV) was known as a good hole injecting material (ionization potential, Ip :5.1eV), an EL device with ITO/PPV/PQx/Metal type structure was suggested. It was shown that the quantum efficiency of the cell was about twice as high as that of ITO/PPV/Metal cell. Related physical and optical properties of PQx derivatives are also investigated.

WEBER'S CLASS NUMBER PROBLEM IN THE CYCLOTOMIC ℤ2-EXTENSION OF ℚ, III

Let hn denote the class number of which is a cyclic extension of degree 2n over the rational number field ℚ. There are no known examples of hn > 1. We prove that a prime number l does not divide hn for all n ≥ 1 if l is less than 109 or l satisfies a congruence relation l ≢ ± 1 (mod 32).

Orientation of linear π-conjugated poly(p-phenylene), poly(thiophene-2, 5-diyl) and poly(2, 2′-bipyridine-5, 5′-diyl) perpendicularly to the surface of carbon and metal substrates. Factors controlling the orientation.

Abstract Vacuum evaporation of π-conjugated poly(p-phenylene), poly(thiophene-2, 5-diyl) and poly(2, 2′-bipyridine-5, 5′-diyl) on carbon substrates affords highly oriented crystalline thin films of the polymer with the polymer chain perpendicular to the surface of the substrates. Electron diffractometory reveals that the order of the orientation of the thin film is affected by substrate temperature, strength of interaction between the polymer molecules and the substrates, and linearity of the polymer molecules.

Photocarrier-transporting kinetics in poly(2,3-di(p-tolyl)quinoxaline-5,8-diyl)

Abstract Photocarrier-transporting kinetics in poly(2,3-di( p -tolyl)quinoxaline-5,8-diyl) are studied by measuring the photocurrent as a function of electric field and temperature in a wide range (70–300 K). The experimental data can be interpreted in terms of a hopping process between localized charge-transporting sites. It is shown that the Poole-Frenkel model is not suitable, but Basslers model is applicable for elucidation of the carrier-transporting mechanism in a high-temperature region (240–300 K). On the other hand, the variable-range-hopping model is adopted to elucidate the photocurrent at low temperatures (70–200 K).

A capitulation problem and Greenberg's conjecture on real quadratic fields

We give a sufficient condition in order that an ideal of a real quadratic field F capitulates in the cyclotomic Z 3 -extension of F by using a unit of an intermediate field. Moreover, we give new examples of Fs for which Greenbergs conjecture holds by calculating units of fields of degree 6, 18, 54 and 162.

Weber's Class Number Problem in the Cyclotomic ℤ2-Extension of ℚ

Let h n denote the class number of ℚ(2 cos(2π/2 n+2)). Weber proved that h n is odd for all n ≥ 1. We claim that if ℓ is a prime number less than 107, then for all n ≥ 1, ℓ does not divide h n .

An algorithm for computing p -class groups of abelian number fields

For an abelian number field F and an odd prime number p which does not divide the degree [F:ℚ], we propose a new algorithm for computing the p-primary part of the ideal class group of F using Gauss sums and cyclotomic units.

On a unit group generated by special values of Siegel modular functions

There has been important progress in constructing units and S-units associated to curves of genus 2 or 3. These approaches are based mainly on the consideration of properties of Jacobian varieties associated to hyper-elliptic curves of genus 2 or 3. In this paper, we construct a unit group of the ray class field k6 of Q(exp(2πi/5)) modulo 6 with full rank by special values of Siegel modular functions and circular units. We note that k6 = Q(exp(2πi/15), 5√-24). Our construction of units is number theoretic, and closely based on Shimuras work describing explicitly the Galois actions on the special values of theta functions.