Takakazu Yamamoto

Preparation and properties of π-conjugated poly(benzimidazole-4,7-diyl)s

Preparation, optical properties, and electrochemical redox behavior of poly(benzimidazole-4,7-diyl)s are reported. Dehalogenation polycondensation of 4,7-dibromobenzimidazole and its derivatives (2-heptyl and 2-phenyl derivatives) with zerovalent nickel complexes gives the corresponding polymers in 72-100% yield. Poly(benzimidazole-4,7-diyl) and its heptyl derivative have molecular weights of 1.3 × 10 4 and 3.8 × 10 4 , respectively, as determined by light scattering measurements. In non-acidic solvents the polymers give rise to one absorption peak at about 300 nm, which is assigned to a π-π * transition occurring in the benzimidazole monomeric unit, and another absorption peak at a longer wavelength, which is considered to originate from the π-π * transition occurring in the π-conjugated main chain. The π-π * absorption peak, as well as the photoluminescence peak of the polymers, are shifted in acidic media due to protonation. The polymers are electrochemically active regarding reduction (or n-doping) and show electrochromism.

π-Conjugated polymers bearing electronic and optical functionalities. Preparation, properties and their applications

Abstract Various π-conjugated polymers are obtained by using organometallic polycondensation mediated by organotransition-metal complexes. For example, Ni(0) complex-mediated dehalogenation polycondensation of dihaloaromatic compounds XArX affords poly(arylene)s (Ar) n . These polymers show interesting electronic and optical properties and have already found several useful future applications such as battery, EL, diode, nonlinear optical device, etc. In this review, preparation, basic properties and practical applications for electronic and optical devices of π-conjugated polymers will be described.

N-Oxides and N-ylides of π-conjugated poly(arylene)s. Preparation and properties of the polymers

Treatment of poly(pyridine-2,5-diyl) PPy, poly(quinoline-2,6-diyl) P(2,6-Q), and poly(naphthyridine-2,6-diyl) P(2,6-N) with H2O2 in acetic acid gives quantitatively N-oxidized products of the polymers, PPy-ox, P(2,6-Q)-ox, and P(2,6-N)-diox, respectively. π-π∗ absorption bands of the original polymers show a hypsochromic shift by 35–50 nm by the N-oxidation. Treatment of PPy and P(2,6-Q) with tetracyanoethylene oxide affords N-ylidated products with a 10–15% degree of N-ylidation. The N-oxidized and ylidated polymers undergo electrochemical reduction in a range of about −1.7 to −2.2V vsAgAg+. The electrochemical reduction is accompanied by colour change, and colours of the reduced polymers are considerably different from those of the original polymers (e.g. PPy). The N-oxidized and -ylidated polymers have a d.c. electrical conductivity of 2.8 × 10−7−3.4 × 10−6 S cm−1.

π-Conjugated polymers containing thiophene-1,1-dioxide-2,5-diyl unit in the main chain

Abstract An alternative π-conjugated copolymer of thiophene-1,1-dioxide and thiophene has been obtained by a Pd-catalyzed reaction, and basic properties of the copolymer are described. The copolymer has a number average molecular weight of 9980 as estimated by GPC, an absorption peak at 490 nm, and an electrical conductivity of 6×10−5 S cm−1 at the non-doped state. Poly(aryleneethynylene)-type polymers containing the thiophene-1,1-dioxide unit have also been prepared.

Electrochemical activity of polypyridine in aqueous acidic media

Abstract Polypyridine (PPy) cast on carbon fibre is reduced at about −0.20 V vs. Ag/AgCl in an aqueous solution of poly(vinyl sulfonic acid), PVSA. The cyclic voltammetric trace is stable for over a thousand scans and gives a discharge capacity of 117 C per gram of polypyridine.

Ultraviolet Photoelectron Spectroscopy of n-Type Conducting Polymers

Abstract Ultraviolet photoelectron spectra were measured using synchrotron radiation for four kinds of π -conjugated polymers, poly(pyridine-2,5-diyl)[Ppy], poly(2,2′-bipyridine-5,5′-diyl)[Pbpy], poly(2-methylantraquinone-1,4-diyl)[P(2Me-1,4-AQ)], and poly(antraquinone-1,5-diyl)[P(1,5-AQ)], which exhibit n-type electrically conducting properties. Upon K-doping of Pbpy, two new states appeared in the originally empty energy gap. This finding indicates that bipolaron bands are formed in K-doped Pbpy. While K-doped Ppy also shows similar gap states, it requires higher dopant concentration to create bipolaron bands than in the case of K-doped Pbpy. The UPS spectra of K-doped P(2Me-1,4-AQ) also show similar gap states, while it is almost absent in K-doped P(1,5-AQ). The changes in electronic structure of these polymers are discussed based on the conformational difference between these polymers.

PREPARATION OF ELECTRICALLY CONDUCTING POLYANILINES BY A NEW METHOD AND ELECTRICAL CONDUCTING PROPERTIES OF THE POLYMERS

Palladium-catalyzed polycondensation between N,N-dichloro-p-benzoquinone diimines and diorganometallic aromatic compounds provides a new route for the synthesis of polyanilines. A polymer composed of dimethyl-p-benzoquinone diimine and thiophene units has an electrical conductivity of about 1 Scm-1 at room temperature, and the temperature dependence of the electrical conductivity follows a variable-range-hopping-type equation.