Yasuo Shirai

Ab initio MO investigations of molecular structures in the ground and first excited states of heterocyclic pyridinium betaine

Abstract The molecular structure in the first excited state of the simplest heteorcyclic pyridinium betaine, (1-pyridinio)benzimidazolate, was investigated through ab initio molecular orbital calculations. The central C-N bond shortens to a nearly double bond character in contrast to the case for the ground state, and the pyridinium ring takes a para-quinoid-like structure. The dipole moment direction in the excited state and the ground state are anti-parallel, and the benzimidazole ring acts as an electron-donating group and the pyridinium ring acts as an electron-withdrawing group, and the first excited state is characterized by an intramolecular charge transfer state. Based on these characteristic features of heterocyclic pyridinium betaines, a new concept for manipulating the molecular dipole moment and molecular first-order hyperpolarizability is proposed.

A new class of second-order non-linear optical material: stilbazolium benzimidazolate derived from alkylsulfonyl substituted stilbazole

A novel stilbazolium benzimidazolate derivative,i.e. 2-(4-{2-[4-(octylsulfonyl)phenyl]ethenyl}pyridinio)benzimidazolate 4a, was prepared by the quaternization reaction of 4-{2-[4-(octylsulfonyl)phenyl]ethenyl}pyridine with 2-chlorobenzimidazole, followed by deprotonation with aqueous ammonia. Poly(methyl methacrylate) (PMMA) thin films containing 10 or 20 mass% of 4a were obtained by spin-coating from their THF solutions on an ordinary cover glass substrate. Second-harmonic generation (SHG) measurements of the obtained thin films were carried out by the Maker fringe method using a Q-switched Nd:YAG laser (1064 nm) as an exciting beam after corona-poling. A poled PMMA film containing 10 or 20 mass% of 4a exhibited a second-order non-linear optical (NLO) coefficient, d33 , of 7.6 or 11 pm V–1 , respectively, which was much larger than the d33 value of a PMMA thin film containing 10 mass% of 2-[4-(2-phenylethenyl)pyridinio]benzimidazolate 4c (d33 1.6 pm V–1) or 2-{4-[2-(4-octyloxyphenyl)ethenyl]pyridinio}benzimidazolate 4d (d33 0.51 pm V–1). There were no significant differences in linear absorption properties of PMMA films containing 4a, 4c or 4d. The introduction of an octylsulfonyl group at the 4′-position of the stilbazole moiety increases the second-order NLO coefficient.

Novel polyamides for second‐order nonlinear optics with side‐chain azo‐NLO‐phores

This article describes the syntheses and second-order nonlinear optical (NLO) properties of a novel type of polyamides with side-chain azo-NLO-phores. Two kinds of polyamides were prepared by condensation polymerization using 3-{N-methyl-4-[(4-methylsulfonylphenyl)azo]anilino]-1-propyl 3,5-diaminobenzoate (DA1) and 5-(3-{4-[4-(N,N-dimethylamino)phenylazo]phenyl}sulfonylpropyl)oxyisophthalic acid (IA1) or 5-(3-{N-methyl-4-[(4-methylsulfonylphenyl)azo]anilino}-1-propyl)oxyisophthalic acid (IA2). In the side chain of polyamide P3, which was obtained from DA1 and IA1, electron-donating and electron-withdrawing groups of the NLO-phores were alternatingly attached. In the side chain of polyamide P4, which was obtained from DA1 and IA2, electron-donating groups of all side-chain NLO-phores were attached to their backbone. The obtained polyamides exhibit relatively good solubility in common organic solvents and provide optical-quality films upon spin-coating. The second-harmonic generation (SHG) measurements of the obtained polyamides were carried out by the Maker fringe method using a Q-switched Nd: YAG laser as an exciting beam after corona-poling at various temperatures, indicating that P3 and P4 exhibit an optimum second-order NLO coefficient, d 33 , of 8.7 and 16.5 pm/V, respectively.

Novel optically transparent polyesters containing a high density of second-order non-linear optically active chromophores

The syntheses and second-order non-linear optical (NLO) properties of novel types of optically transparent polyesters containing a high density of second-order NLO-active chromophores are described. The chromophores used in this study contained either a perfluorooctyl- or an octyl-sulfonyl moiety as the electron-withdrawing group at the π-conjugating sites. The polyesters are prepared by condensation polymerization between isophthalic acid derivatives and 2-[N-(2-hydroxyethyl)-4-(perfluorooctylsulfonyl)anilino]ethanol by the use of triphenylphosphine and diethyl azodicarboxylate as the condensation reagents. The amorphous polyesters obtained, the optical transparency of which was down to 390 nm, exhibited good solubility in common organic solvents and provided optical-quality films by spin-coating. In addition, second-harmonic generation (SHG) measurements of spin-coated films of the polyesters were carried out by the Maker fringe method using a Q-switched Nd : YAG laser as the exciting beam after poling treatment. One of the polyesters, which was prepared from 5-{2-[N-methyl-4-(perfluorooctylsulfonyl)anilino]ethoxy}isophthalic acid and 2-[N-(2-hydroxyethyl)-4-(perfluorooctylsulfonyl)anilino]ethanol, exhibited the desired optical-transparency and a second-order NLO coefficient, d33, of 3.0 pm V–1.

A new class of second-order non-linear optical material:stilbazolium benzimidazolate covalently bound to polymer backbone

This paper describes the first example of the preparation of stilbazolium benzimidazolate covalently bound to polymer backbone using a novel methacrylate monomer, 2-{4-[2-(4-methacryloyloxyphenyl)ethenyl]pyridinio}benzimidazolate. A free radical copolymerization of 2-{4-[2-(4-methacryloyloxyphenyl)ethenyl]pyridinio}benzimidazolate (1 equiv.) with butyl methacrylate (6 equiv.) provided a methacrylate polymer containing 1.7 mol% of betaine units. The resulting polymer exhibited a glass transition temperature of 30 °C. The number-average (M n ) and weight-average (M w ) molecular masses were 36 900 and 79 300, respectively, estimated by GPC measurement. The second-order non-linear optical property of the obtained polymer was investigated by second-harmonic generation (SHG) measurements applying the Maker fringe method using a Q-switched Nd:YAG laser (1064 nm) as an exciting beam after corona-poling, indicating that the d 33 value of the resulting copolymer was 5.1 pm V -1 .

Novel concept for non-destructive readout method for photochromic rewriteable memory devices

Abstract A new concept for a non-destructive readout method for a photochromic rewriteable device is proposed based on a solvatochromic dye-linked photochromic dye system. From the theoretical molecular orbital calculations for the model compound, it was shown that the UV-Vis absorption band of the solvatochromic dye unit is sensitive to the conformation of the nearby photochromic unit. These calculations indicate that light corresponding to the UV-Vis absorption band of the solvatochromic dye unit can be used as the non-destructive readout light, since light in this region is found inactive to irradiation for achieving the photochromic reaction of the photochromic dye unit.

Polyamides alternately substituted with an aliphatic cyclic moiety and an NLO-phore for second-order nonlinear optics

This article describes the synthesis and second-order nonlinear optical (NLO) properties of polyamides containing an alternating arrangement of cholesteryl or menthyl moieties and an NLO-phore, i.e., N,N-dialkyl-4-mtroaniline in the side chain. The polyamides were prepared by condensation polymerization of 5-[2-(N-methyl-4-nitroanilino)ethoxy]isophthaloyl chloride with cholesteryl (P1) or L-menthyl (P2) 3,5-diaminobenzoate. The resulting polyamides P1 and P2 exhibit high glass transition temperatures (T g ) around 200 C and good solubilities in common organic polar solvents. Optical-quality films of P1 and P2 were obtained by spin-coating. The second harmonic generation (SHG) measurements of the spin-coated films of P1 and P2 were carried out by the Maker fringe method using a Q-switched Nd:YAG laser (1064 nm) as exciting beam after corona-poling: they indicate that P1 and P2 exhibit a second-order NLO coefficient. d 33 , of 10 pm/V. The orientational behavior of the NLO-phores in P1 is specific for the poling process. A noncentrosymmetric alignment of the NLO-phores in P1 was induced by corona-poling at a temperature lower than T g , i.e. at 100 C. Additionally, it was found that the noncentrosymmetric alignment of NLO-phores in P1 is inhibited over 160 C due to the para-crystalline aggregation of cholesteryl moieties as deduced from the SHG measurements and X-ray diffraction analysis.

Orientational dynamics in the crystalline and amorphous states of side-chain liquid crystalline polysiloxane probed by second harmonic generation

The orientational behaviour of mesogenic chromophores in side-chain liquid crystalline polysiloxane subject to an external electric field was investigated by the measurement of second harmonic generation (SHG). The rise and decay rates of the electric-field-induced SHG intensity in the crystalline state were found to be slower than those in the amorphous state; furthermore, the SHG intensity in the crystalline state was found to be weaker than that in the amorphous state. Analysis of the rise and decay rates of the electric-field-induced SHG intensity suggested that the mesogenic chromophores in the amorphous state move independently with other mesogenic chromophores and with the siloxane backbone, whereas those in the crystalline state move cooperatively with them.

Spacer Length Dependence of Tilt Angle of Mesogenic Chromophores of Side-Chain Liquid-Crystalline Polysiloxanes

Abstract The orientational behavior for a series of side-chain liquid-crystalline polysiloxanes incorporating azo chromophores, i.e., poly(3-{4-[(4-nitrophenyl)azo]phenyl]oxycarbonyl}propylmethylsiloxane)-co-(3-carboxypropylmethylsiloxane) (P1), poly {3-[(6-{[4-[(4-nitrophenyl)azo]phenyl]oxy}hexyl)oxycarbonyl]propylmethylsiloxane}-co-(3-carboxypropylmethylsiloxane) (P2), and poly{3-[(11-{[4-[(4-nitrophenyl)azo]phenyl]oxy}undecyl)oxycarbonyl]propylmethylsiloxane}-co-(3-carboxypropylmethylsiloxane) (P3) were investigated by UV-Vis and polarized FTIR-ATR spectroscopy as well as X-ray diffraction measurement using their thin films. P1 exhibited highly-ordered smectic and nematic phases as the mesophases. On the other hand, P2 and P3 showed only smectic C phase. The mesogenic chromophores of these polymers in smectic phases and the once-annealed solid were spontaneously aligned nearly normal to a substrate surface. In the case of P1, the tilt angle of the mesogenic chromophores in the nematic phase was found t...

Novel Developing Method of Color Formers by Cation Exchange Membranes and Its Stability of Image Dyes.

画像記録材料としていくつかの優れた特性をもつ酸発色型の発色剤の顕色法として受像層と顕色機能を兼ね備えた陽イオン交換膜による新しい方法について提案し,それらの発色挙動や画像安定性の向上など画像記録技術にとって有益な多くの知見を得た。アゾメチン,スピロビランおよびジフェニルメタン系の 3 種類の発色剤は,強酸性のスルホン酸基を固定イオンにもつフッ素系の陽イオソ交換膜を Li+, Na+, K+, Mg2+, Ca2+ および Ni2+ のような金属イオンで交換処理するとそれらと反応し発色する。これら交換膜と発色剤溶液の発色反応は,交換した金属イオンの電気陰性度に依存し,同じ電荷数の金属イオンの場合,それら金属の電気陰性度が大きくなると反応速度も増加した。またこれらの発色反応は,イオン交換処理液の pH 値,現像の温度,交換膜中の含水量などに依存した。陽イオン交換膜により形成された染料の耐光性や暗中での熱反応に対する安定性は,スピロピラン染料の耐光性を除き,顕色剤として光や熱に安定な染料を形成することが知られている Ni-サリチル酸錯体で形成された同じ種類の染料と比較していちじるしく向上した。