Synthetic Metals (v.159, #9-10)

Preface by Kazuo Akagi; Keiichi Kaneto (761).

Side-chain type liquid crystalline polyacetylene, which has mesogenic moieties as side chains, is one of the promising materials for practical applications in the electronics. Micropatterning of the conductive polymer is a significant issue in this field. We show a simple method to fabricate micropatterns of side-chain type liquid crystalline polyacetylene derivative. Under dry condition, stripes patterns and lattice pattern were formed based on the fingering instability and stick-slip motion of the receding meniscus. Honeycomb-patterned polymer film was obtained by casting polymer solution under humid condition. The micropatterns drastically changed by changing solution concentration and preparation conditions.
Keywords: Micropatterning; Liquid crystalline polyacetylene; Self-organization;

Scanning tunneling microscopic (STM) observation of an array of 5,10,15,20-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin molecules deposited on a Au(1 1 1) surface revealed dark and bright spots within the regular two-dimensional pattern, which are due to conformational diversity of the adsorbed molecules caused by distortion of the porphyrin core. With this structure, two-digit information can be input with ca. 2-nm interval, which would correspond to an information density of 25 terabit/cm2 if exploited in a memory device.
Keywords: Porphyrin; Scanning tunneling microscopy; Molecular array; Two-dimensional pattern; Information density;

In recent experiments, the signal-to-noise ratio and the photon pair correlation are measured simultaneously by improving the Hanbury-Brown and Twiss method. We show that judgement on whether the background noise obeys Poisson statistics or not is possible from the data of such measurements. If the background is subject to Poisson statistics, the results of both measurements enable to estimate the photon pair correlation in the absence of noise from that measured under background noise. The method is useful to remove the effect of background noise from the photon correlation measured by exciting multichromophore systems. We also show that the normalized photon pair correlation is not necessarily zero in the absence of background noise when single photon is emitted from multiple excitons as a result of the competition among the pair annihilation, and the unimolecular nonradiative and radiative processes.
Keywords: Photon statistics; Excitons;

The reduction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with an equivalent amount of alkali metal (Li, Na, K, KC8) in THF produced the corresponding disilyne anion radicals 2a–c. Their EPR spectra are independent of the metals used in THF, indicating that the disilyne anion radical species exists as solvent-separated ion pairs in polar solvents. The one-electron reduction also occurred with potassium in toluene to produce the potassium salt of the anion radical 3, which was isolated as extremely air- and moisture-sensitive dark brown crystals. The molecular structure of 3 was established by X-ray crystallography, which showed that the potassium ion is solvated by one toluene molecule. The EPR spectrum of 3 in toluene showed the interaction of the anionic silicon atom with the K+ ion.
Keywords: Anion radical; Disilyne; Reduction; Silicon–silicon triple bond; X-ray crystallographic analysis;

Novel lead iodide-based layered perovskite compounds, which contain fullerene derivatives, N-methyl-2-(4-ammoniumphenyl)-fulleropyrrolidine iodide (AmPF) and N-(n-dodecyl)-2-(4-ammoniumphenyl)-fulleropyrrolidine iodide (C12AmPF), in their organic layers were fabricated as thin solid films by spin-coating. The XRD profiles showed that (AmPF)PbI4 molecules were arranged in a closer-packing form, compared with (C12AmPF)PbI4. The photoluminescence spectra of thin films suggested the presence of energy transfer between C60 moiety and lead(II) iodide layers, which led to the disappearance of fluorescence peak at 517 nm and the appearance of a new fluorescence peak at 780 nm. (AmPF)PbI4 and (C12AmPF)PbI4 films exhibited photoconductivity when ultraviolet light was irradiated, and the photocurrent values with applying 1.0 V bias voltage were 1.77 μA and 1.48 × 10−2  μA, respectively.
Keywords: Fullerene derivative; Perovskite; Optical property;

Synthesis and properties of helical substituted polyacetylenes by Fumio Sanda; Toshio Masuda (780-783).
Optically active N-propargylamides polymerized with rhodium catalysts into helical polymers with predominantly one-handed screw sense. It was confirmed that hydrogen bonding between the amide groups in the side chains played an important role to stabilize the helical structure. Poly(1-methylpropargyl alcohol)s and the esters took helical structures stabilized by the steric effect of methyl group adjacent to the main chain.
Keywords: Chiral; Helix; Polyacetylene;

Poly(fluoroalkylsilane-b-dialkylsilane)-based chemosensory material for fluoride with high sensitivity, selectivity and solubility by Masanobu Naito; Masashi Nakamura; Takuma Kawabe; Woojung Chung; Hisanari Onouchi; Michiya Fujiki (784-787).
Poly((i-butyl-n-decylsilane) x -b-(methyl-3,3,3-trifluoropropylsilane)1−x ) (PSi3) was prepared using a simultaneous block copolymerization with a conventional Wurtz-type condensation reaction. The block-like polysilane copolymer showed high selectivity and sensitivity toward fluoride ion (F) even in the coexistence of the halide ions (Cl, Br, and I), and high solubility to common organic solvents with the dielectric constants (ɛ′) between 1.88 (n-hexane) and 9.04 (benzotrifluoride). Such unique characteristics were derived from poly(methyl-3,3,3-trifluoropropylsilane) (PSi1) and poly(i-butyl-n-decylsilane) (PSi2) unit in the copolymer, respectively. In addition, sensitivity to F and solubility in organic solvents were successfully optimized by adjusting the composition ratio between PSi1 and PSi2 unit.
Keywords: Polysilane; Chemosensor; Fluorine; Block copolymer; Wurtz coupling;

2,6,10-Tris[5′-(5-hexyloxyphenyl-2,2′-bithiophenyl)]-3,7,11-tris(hexyloxy)tripheneylene (2) was designed and synthesized as a π-conjugated platform to produce its tris(cationic radical) derivative (1) in a non-Kekulé and nondisjoint fashion. An electrochemical study revealed the chemically reversible redox property of 2. Gaseous antimony pentachloride-doping of 2 dispersed in a polystyrene matrix gave its cationic radical. It was chemically stable with a half-life >2 weeks and displayed a triplet ground state based on an ESR measurement. A high-spin state with S  = 3/2 for 1 was proved by the magnetization and magnetic susceptibility.
Keywords: Arylthiophene; Triphenylene; Non-Kekulé molecule; π-Conjugated molecule; Ferromagnetic interaction;

Synthesis, properties, and solid-state assemblies of β-alkyl-substituted dipyrrolyldiketone BF2 complexes by Hiromitsu Maeda; Yohei Haketa; Yuya Bando; Shohei Sakamoto (792-796).
In this paper, the synthesis and solid-state structures of β-alkyl-substituted dipyrrolyldiketone BF2 complexes are discussed; these complexes can function as π-conjugated acyclic anion receptors (“molecular flippers”) and are potential building subunits of anion-responsive π-conjugated oligomers or polymers. Modes of the solid-state assemblies in these complexes determined by performing single-crystal X-ray analysis are found to depend on the lengths of the alkyl chains at the β-positions. A β-methyl-substituted receptor has a highly planar structure, which efficiently forms stacking assemblies in the core π-plane in the solid state, while a β-ethyl-substituted receptor shows no stacking assemblies due to the presence of bulky ethyl moieties, which form only dimeric structures by hydrogen bonding. β-Alkyl-substituted anion receptors can be used not only as monomer units of stimuli-responsive polymeric macromolecules but also as components of solid-state electronic materials.
Keywords: Anion receptors; π-Conjugated molecules; Crystal structures; Molecular assemblies; Pyrrole derivatives;

Photovoltaic performance and charge carrier mobility of dendritic oligothiophene bearing perylene bis(dicarboximide) groups by Yutaka Ie; Toshihiko Uto; Akinori Saeki; Shu Seki; Seiichi Tagawa; Yoshio Aso (797-801).
We have developed dendritic oligothiophenes bearing perylene bis(dicarboximide) units and investigated the photophysical and electrochemical properties, photovoltaic performance, and charge carrier mobility. The extended conjugation of the central oligothiophene unit led to an improved performance of the thin-film photovoltaic device and charge carrier mobility of 1.3 × 10−2  cm2  V−1  s−1 estimated by the combination of time-resolved microwave conductivity (TRMC) and transient absorption spectroscopy (TAS) measurements.
Keywords: Organic photovoltaic device; Oligothiophene; Dendrimer; Carrier mobility;

Distributed feedback lasing coupled with stimulated resonant Raman scattering in polyphenylenevinylene films by H. Yanagi; N. Kawazu; R. Takeaki; S. Tomita; K. Yamashita; K. Oe (802-804).
Thin film waveguides of polyphenylenevinylene were formed on a distributed feedback resonator. Light emission under pulsed optical pumping was measured as a function of excitation wavelengths. A distributed feedback lasing appeared constantly at 635 nm. In addition, an emission peak due to stimulated resonant Raman scattering emerged and its peak position shifted according to the excitation wavelength. When the latter peak just overlapped with the former one, the emission intensity was enhanced and its peak width and background noise by amplified spontaneous emission were reduced. The coupling of Raman scattering with the feedback mode would be a useful technology for development of a plastic laser.
Keywords: Distributed feedback laser; Stimulated resonant Raman scattering; Polyphenylenevinylene; Polymer film waveguide;

Single-photon emission from a single nanoparticle consisting of a single conjugated polymer chain by Sadahiro Masuo; Tomoya Tanaka; Takumi Murakami; Akito Masuhara; Shinjiro Machida; Hitoshi Kasai; Hidetoshi Oikawa; Akira Itaya (805-808).
Single-photon behavior in the emission from a single nanoparticle consisting of a single poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV, molecular weight: 2,600,000 amu) chain has been investigated. Photon correlation measurements of a number of single nanoparticles revealed that the probability of single-photon emission from the single nanoparticles clearly increases, compared with that of single chains embedded in host polymer matrices, poly(methyl methacrylate) (PMMA) and polystyrene (PS). The result suggested that even a single MEH-PPV chain with high molecular weight, which does not exhibit single-photon emission in PMMA and PS, is forced to exhibit single-photon emission by adopting “compact” chain conformation like nanoparticle. Efficient exciton migration and exciton annihilation processes in the compact chain conformation most probably result in the efficient single-photon emission from the single nanoparticle. The present results indicate that multi-quantum systems consisting of a large number of chromophores, such as the MEH-PPV, can be made to behave as single-photon sources by appropriately controlling their size.
Keywords: Conjugated polymer; MEH-PPV; Nanoparticle; Single molecule; Single photon; Antibunching;

Picosecond time-resolved infrared absorption spectra of the photoexcited states of a spin-coated film of regioregular poly(3-hexylthiophene) (RR-P3HT) have been recorded at 77 K. The time-resolved photoinduced infrared absorptions due to electronic transitions at 2500 cm−1 and vibrational transitions at 1575 cm−1 have fast and slow decay components. By comparing the picosecond time-resolved infrared absorption spectrum of long-lived (slow decay component) transient species with the doping-induced infrared difference spectrum of RR-P3HT, the long-lived transient species are assigned to polarons. The short-lived transient species are assigned to singlet excitons and/or polaron pairs.
Keywords: Time-resolved infrared absorption; Photoexcited dynamics; Regioregular poly(3-hexylthiophene); Polaron;

Metal-based nanoparticles templated with dendrimers have recently attracted much interest to control particle sizes strictly. However, the standard deviation of the obtained particles is larger than that of the single-mass Au clusters (0.2 nm). We succeeded the subnanosize-control of TiO2 particles (both of rutile and anatase crystal structures based on the difference in the synthesis methods) with a standard deviation of 0.2 nm, using finely controlled metal assembly on a phenylazomethine dendrimer (DPA G4). The optical absorption spectra of the obtained particles revealed that the quantum size effect and the difference in the crystal structure, such as rutile and anatase, exists less than 2 nm particle sizes. A semi-empirical effective mass approximation, introduced a new concept; apparent reduced mass, describes the size dependency and the difference based on the crystal structure in the bandgap energy of the indirect and direct transition.
Keywords: Dendrimer template; Metal oxide nanoparticles; Quantum size effect;

Attachment of poly[(ethoxyhexylsilylene)oligothienylene]s to inorganic oxide surface by Joji Ohshita; Junya Matsukawa; Tomonori Iwawaki; Shigenori Matsui; Yousuke Ooyama; Yutaka Harima (817-820).
Poly[(ethoxyhexylsilylene)quarter- and -quinquethienylene]s (EHSxT, x  = 4 and 5) were prepared by Stille-coupling reactions of bis(bromothienyl)ethoxyhexylsilane and bis(tributylstannyl)bi- and -terthiophenes, respectively. Treatment of indium tin oxide (ITO) and TiO2 electrodes with solutions of EHSxT in chloroform at 40 °C led to the formation of the polymer-attached electrodes. An application of the EHS5T-attached TiO2 electrode to dye-sensitized solar cell was examined.
Keywords: Oligothiophene; Organic–inorganic hybrid; Dye-sensitized solar cell;

A new organogelator based on 1,3,5-tris(phenylisoxazolyl)benzene by Takeharu Haino; Hiroshi Saito (821-826).
1,3,5-Tris(phenylisoxazolyl)benzene derivatives possessing polar and nonpolar side chains were synthesized. The microscopic gel morphology was confirmed by using FESEM, TEM, and XRD measurements. The amphiphilic nature of the tris(phenylisoxazolyl)benzene derivative gives rise to the lamellar structure, responsible for the formation of the fibrous bundles. The intertwined networks of the bundles immobilize the alcoholic solvents, and result in the formation of the organogels.
Keywords: Gel; Self-assembly; Aromatic stacking;

We describe (i) the evaluation of bundled degrees of single-walled carbon nanotubes (SWNTs) in SWNT/UV-curable resin composite films based on the intensity change in the radial breading mode (RBM) of their Raman spectra at a 785-nm excitation, and (ii) the thermal conductivity measurements of the composites films using the temperature wave analysis method. The homogeneous dispersion of the SWNTs produced a gradual increase in the thermal conductivity with an increase in the SWNT loading up to 5.0 wt%. This observed behavior is quite different from that of the electric conductivity of the composite films, in which the electric conductivities dramatically decrease at around only a 0.05 wt%-SWNT loading as previously reported.
Keywords: Carbon nanotubes; Dispersion; Thermal conductivity; Composite films;

In this study, Fe2O3·NiO/PANi nanocomposites were prepared and their anticorrosion properties were investigated. The Fe2O3·NiO nanoparticles were synthesized by precipitation–oxidation methods. Fe2O3·NiO–PANi nanocomposites were prepared by in situ polymerization of aniline monomer in the presence of Fe2O3·NiO nanoparticle. The structure of the polymer nanocomposite was characterized by SEM and X-ray method. The electrical conductivity, magnetic properties and anticorrosion properties of the materials were examined by the conventional four probe method, vibrating magnetometer and by impedance measurement method. The results show that the Fe2O3·NiO nanoparticles have the uniform size with the size ranging from 50 to 60 nm. By the formation of polymer nanocomposite, the Fe2O3·NiO phase is well dispersed in the PANi polymer matrix. But the Fe2O3·NiO nanoparticles are not exfoliated from its agglomerate structure. The polymer nanocomposite showed both magnetic and conductive properties. With increasing Fe2O3·NiO content, both the saturated magnetization and the coercive force increase and reach the value of 0.31 emu/g and 162.56 Oe by the Fe2O3·NiO content of 5%, respectively. In contrast, the electrical conductivity of the polymer nanocomposite decreases with increasing Fe2O3·NiO content from 0.353 S/cm of neat PANi to 0.075 S/cm by the Fe2O3·NiO content of 5%. From the anticorrosion investigation, it was revealed that the protective performance of polyurethane paint containing Fe2O3·NiO/PANi nanocomposite was significantly improved with increasing Fe2O3·NiO/PANi content.
Keywords: PANi; Magnetic properties; Anticorrosion;

Hydrophobic Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) [F8BT] formed an ideal spread monolayer on a water surface by the cospreading method with liquid crystal molecule, 4′-pentyl-4-cyanobiphenyl [5CB]. The F8BT/5CB hybrid monolayers were characterized by surface pressure–area (πA) isotherm measurements and atomic force microscopy (AFM). F8BT does not form a homogeneous monolayer by direct spreading on water from a single solution. The mixed film of two components, F8BT and 5CB, gave a characteristic pressure lift-off attributed to the hybrid monolayer above the 5CB plateau. AFM observation revealed that the spread monolayer of the F8BT formed on the top of the 5CB monolayer on water with the thickness of ca. 1.7 nm. The F8BT/5CB hybrid monolayers could be fully transferred onto a solid substrate, and pure F8BT monolayers were obtained after volatilization of 5CB by gentle heating. Polarized UV–vis absorption spectra showed that the main chain of F8BT preferentially oriented perpendicular to the compressive direction at the surface pressure of 10 mN m−1 on water.
Keywords: Langmuir–Blodgett method; Conjugated polymers; Molecular orientation; Spread monolayer; Cospreading method;

Stability of electrochemomechanical strains in polypyrrole films using ionic liquids by Kentaro Yamato; Kazuo Tominaga; Wataru Takashima; Keiichi Kaneto (839-842).
Electrochemomechanical strain (ECMS) of conducting polymers, polypyrrole (PPy) films was studied using several kinds of ionic liquids and the mixed solution with organic solvents from the view points of strain and stability. The PPy films, which were electrodeposited from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), showed porous morphology. The ECMS in the films operated in ionic liquids was less than 5%, demonstrating a cation movement behavior and stable cycling. By the operation in ionic liquid/propylene carbonate (PC) mixed solution, the ECMS increased up to 24% showing the anion movement, and gradually decreased upon cycling to 16% at 10th cycle. The strain and stability of the ECMS in mixed electrolyte solution with various ratios of the ionic liquid and PC were studied and discussed in terms of mechanisms of ECMS in mixed solutions.
Keywords: Conducting polymer; Polypyrrole; Electrochemomechanical strain; Ionic liquid; Soft actuator; Artificial muscle; Strain;

Intra-molecular mobility of holes along rod-like helical Si backbones in optically active polysilanes by Yoshihito Honsho; Atsushi Asano; Shu Seki; Takeyoshi Sunagawa; Akinori Saeki (843-846).
Intra-molecular mobility of positive charge carriers in poly(n-hexyl-[S]-2-methylbutylsilane) (PHMBS) films doped with N,N′-bis(2,5-di-tert-buthylphenyl)-3,4,9,10-perylenedicarboximide (PDI) is studied by time-resolved microwave conductivity (TRMC) measurements. PHMBS with optically active side chains has a rod-like tightly locked Si catenation with unlikely long persistence length compared with conventional dialkyl-substituted polysilanes. It was found that PDI is a suitable electron acceptor for PHMBS as it provides the high product of photo carrier generation yield ϕ as ∼0.08% under an excitation at 355 nm. The efficient electron transfer reaction from PHMBS to PDI gives clear conductivity transients ascribed to the positive charges on the Si catenation of PHMBS by TRMC measurements. The estimated value of isotropic mobility along the tightly locked Si catenation is 0.36 cm2  V−1  s−1, suggesting the presence of mobile holes on the backbones of PHMBS.
Keywords: Polysilane; Optically active; Microwave; Conductivity; Mobility;

Densely packed organic nanocrystals ultrathin film using a liquid–liquid interface by J. Matsui; T. Shibata; K. Yamamoto; T. Yokoyama; A. Masuhara; H. Kasai; H. Oikawa; T. Miyashita (847-850).
We report a fabrication of densely packed polydiacetylene nanocrystal film using a liquid–liquid interface. Polydiacetylene (pDCHD) nanocrystals was dispersed into water solution by reprecipitation method from a good solvent. Then, hexane was added to the water dispersion to create the liquid–liquid interface. pDCHD nanocrystals were assembled at the interface, when ethanol was added to the pDCHD water dispersion–hexane solution. The assembled film was transferred onto a solid substrate and the film morphology was observed by scanning electron microscope (SEM). With addition of 10 vol% of ethanol to 2.5 mM of pDCHD water dispersion–hexane solution, a densely packed pDCHD film is fabricated. Optical and electrical properties of the pDCHD film are discussed by UV–vis spectroscopy and current–voltage measurement.
Keywords: Self-assembly; Polydiacetylene nanocrystal; Liquid–liquid interface;

It has been shown that the films of a soluble conjugated polymer poly[(9,9-dioctyl-2,7-divinylene fluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] for electronic devices can be prepared by the electrophoretic deposition with polymer suspensions derived from dilute polymer solutions which are so dilute that the conventional spin-coating technique is not applicable. For example, a 100 nm-thick film can be prepared on an indium-tin-oxide (ITO) electrode from a suspension from solution containing 0.1 g/l of the polymer. The thickness of the polymer film deposited is found to be almost proportional to the concentration of the polymer, and the linearity down to 5.0 × 10−3  g/l is confirmed. On the other hand, it has been found that coating the ITO electrode with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) salt results in low and nonlinear deposition rate.
Keywords: Conjugated polymer; Electrophoretic deposition; Dilute solution; Poly(3,4-ethylenedioxythiophene);

Synthesis of poly(1,3-phenyleneethynylenes) membranes having one-handed helical conformation without any chiral side groups by in-situ desubstitution of d-menthoxy groups by Makoto Inoue; Masahiro Teraguchi; Toshiki Aoki; Shingo Hadano; Takeshi Namikoshi; Edy Marwanta; Takashi Kaneko (854-858).
In this study, we synthesized four chiral helical poly(phenyleneethynylenes) having optically active menthoxycarbonyl groups and desubstituted the chiral groups in membrane state. Polycondensations of (+)-menthyl 3,5-diethynylbenzoate with (+)-menthyl 3,5-diiodobenzoate, 1,2-diiodobenzenen, 1,3-diiodobenzene, and 1,4-diiodobenzene using PdCl2(PPh3)2–PPh3–CuI were afforded helical polymers in good yields (named as PMtMt, o-PMtH, m-PMtH, and p-PMtH, respectively). Among them, PMtMt in a mixture of chloroform/benzene showed the largest Cotton effect in absorption region and gave self-supporting membrane by solvent-casting method. PMtMt membrane also showed a Cotton signal similar to that observed in solution. Desubstitution of PMtMt proceeded quantitatively by immersing the membrane into alkaline solution at room temperature for 3 days. The desubstituted PMtMt membrane showed circular dichroism (CD) signals similar shape to that of the original membrane in the UV region in despite of the polymer having no chiral moieties except for helical conformation. This is the first example of synthesis of chiral helical poly(phenyleneethynylenes) without the coexistence of any other chiral moieties.
Keywords: Conjugated polymer; Poly(phenyleneethynylene); One-handed helical polymer; Desubstitution; Chiral polymer membrane;

Si (monosilane, disilane, and disiloxane) unit-bridged diphenylamine-containing poly(arylene) PARs were prepared and properties of PARs were compared with the relative Si unit-bridged diphenylamine homopolymers. PARs were prepared by palladium-catalyzed polycondensation between Si unit-bridged diphenylamine and distannyl- or diboryl-aromatic compound. PAR with disiloxane unit-bridged diphenylamine was also prepared by oxidation of PAR with disilane unit-bridged diphenylamine. Optical properties and electrochemical properties of PAR depended on not only bridging Si unit but also introduced arylene unit.
Keywords: Diphenylamine; Si-bridging unit; Poly(arylene); Palladium;

Synthesis of an optically active poly(aryleneethynylene) bearing galvinoxyl residues and its chiroptical and magnetic properties by Takashi Kaneko; Hiromasa Abe; Takeshi Namikoshi; Edy Marwanta; Masahiro Teraguchi; Toshiki Aoki (864-867).
We synthesized an optically active poly(binaphthyl-6,6′-diylethynylene-1,3-phenyleneethynylene) with pendant galvinoxyl residues. The hydrogalvinoxyl precursor polymer was given by polymerization of (1,3-diiodophenyl)hydrogalvinoxyl and 6,6′-diethynyl-2,2′-dihexyloxybinaphthyl using Pd(PPh3)4 catalyst (M w  = 4.6 × 104, M w/M n  = 3.0). The polymer yielded the corresponding polyradical with high spin concentration by treatment of the polymer solution with PbO2. In the CD spectra of the polymer and polyradical taken in various solutions, clear Cotton effects were observed in the absorption region of the binaphthyl chromophore, while no Cotton effect was observed in that of the galvinoxyl chromophore. On the other hand, in the MCD, Faraday effects were observed in the absorption region of the backbone and galvinoxyl chromophore. The static magnetic susceptibility of the chiral polyradical was measured using a SQUID magnetometer, and showed weak antiferromagnetic interaction.
Keywords: Conjugated polymer; Polyradical; Phenoxyl; Poly(aryleneethynylene); Circular dichroism; Chiral polymer;

Two-photon excited states in charge-transfer type conjugated polymers by Hideo Kishida; Keisuke Hirota; Hiroshi Okamoto; Hisashi Kokubo; Takakazu Yamamoto (868-870).
We have investigated two-photon excited states of charge-transfer (CT) conjugated copolymers, poly(aryleneethynylene) (PAE) and poly(thiophene-alt-thiazole) (PThTz), using two-photon absorption and electroabsorption methods. The fitting analysis of the experimental spectra reveals that the two-photon excited states are located 0.5–0.6 eV above the one-photon excited states. These results are compared with nonlinear optical spectra of another CT polymer and a non-CT polymer.
Keywords: Conjugated polymers; Nonlinear optical properties; Charge transfer; Electroabsorption; Two-photon absorption;

Optical and electrical anisotropies of polydiacetylene derivative film aligned by shear stress by Masahiro Fujimoto; Mamoru Ishida; Akihiko Fujii; Yoshimine Sakamoto; Norifumi Fujita; Seiji Shinkai; Masanori Ozaki (871-874).
The molecular alignment of polydiacetylene (PDA) derivatives and their optical and electrical properties of thin films based on PDA derivatives have been studied. The PDA derivatives were aligned depending on the direction of applied shear stress in the film. From measurements of the polarized absorption and current–voltage characteristics, the optical and electrical anisotropies have been observed, that was discussed by taking the PDA main chain alignment into consideration.
Keywords: π-Conjugated polymer; Polydiacetylene; Anisotropy; Shearing; Molecular alignment;

Carrier mobility of a columnar mesophase formed by a perfluoroalkylated triphenylene by Yasuo Miyake; Akihiko Fujii; Masanori Ozaki; Yo Shimizu (875-879).
The carrier mobility of a hexagonal columnar (Colh) mesophase was evaluated by a time-of-flight (TOF) technique for hexa(1H,1H,2H,2H3H,3H-perfluorononyloxy)triphenylenes (F6/C9). The photocurrent decay curves were clearly observed in the Colh mesophase to show an ambipolar nature and the carrier mobility is in the order of 10−4  cm2  V−1  s−1 for both positive and negative charges. The mobility is not of temperature-independent and three regions in temperature were recognized in which the activation energies are different to each, indicating different conditions of charge transports within the columnar structure are derived from the perfluoroalkyl chains. The comparison of temperature dependence to the corresponding non-fluorinated hexanonyloxytriphenylenes (C9OTP) indicates that the dynamical aspect of the peripheral chains profoundly affects that of the central triphenylenes in the segregated columnar structure.
Keywords: Liquid crystal; Columnar phase; Fluorine; Molecular dynamics; Carrier mobility;

Synthesis and properties of optically functionalized polythiophene having porphyrin side-chain by Koji Iwasaki; Atsushi Kimoto; Shin-ichi Naya; Fumiyasu Iwahori; Jiro Abe (880-884).
The synthesis and photochemical properties of poly[1,3-bis(dithienyl)benzene] having a porphyrin group as a side-chain were studied. As a target monomer, 1,3-bis(dithienyl)benzene with an ethynylporphyrin substituent was synthesized by Pd-catalyzed cross-coupling reactions. The electrochemical polymerization of the monomer afforded a conductive polymer film on the ITO-coated glass. The spectroelectrochemistry of the polymer was investigated to clarify the electrochemical oxidation behavior. The current density of the target polymer showed a good photoresponse and the much larger photocurrent was observed as compared with the dark current.
Keywords: Polythiophene; Photoelectrochemical cell; Solar cell; Electrochemical polymerization;

Preparation of hybrid films of aluminosilicate nanofiber and conjugated polymer by Nattha Jiravanichanun; Kazuya Yamamoto; Atsushi Irie; Hideyuki Otsuka; Atsushi Takahara (885-888).
We have demonstrated the preparation of hybrid films of aluminosilicate nanofiber (imogolite) and water-soluble poly(p-phenylene) (WS-PPP), which has sulfonate groups. The imogolite/WS-PPP hybrid gel could be prepared by mixing a solution of these two materials and subsequent centrifugation. The aluminol (Al―OH) groups on the surface of imogolite would be protonated under acidic conditions to afford Al―OH2 + groups that can interact with sulfonate groups (SO3 ) of WS-PPP. Based on this ionic interaction, a layer-by-layer (LBL) assembly was applied to fabricate the hybrid films of imogolite nanofibers and WS-PPP. The deposited amounts of WS-PPP and imogolite were measured by quartz crystal microbalance (QCM) measurements and scanning electron microscopy (SEM) observation. Atomic force microscopy (AFM) observation revealed that imogolite nanofibers were well networked in the LBL hybrid film.
Keywords: Conjugated polymers; Organic/inorganic hybrids; Nanofiber; Imogolite; Layer-by-layer;

Gain-narrowed emissions from oligomer crystals assisted by interference exposure by Takeshi Yamao; Takeshi Inoue; Yuki Okuda; Takashi Ishibashi; Shu Hotta; Naoto Tsutsumi (889-892).
We have carried out emission measurements on semiconducting oligomer crystal slabs using interference exposure with a Lloyd mirror. We used this mirror for the purposes of both photopumping the oligomer slab and fabricating a diffraction grating on an insulating polymer supported with a glass substrate. With the latter purpose we made a distributed feedback (DFB) structure by laminating the insulating polymer with another oligomer slab. The resulting DFB structure was further served for the laser excitation measurement. The emission measurements reveal that a few emission lines are selectively intensified and gain-narrowed.
Keywords: Interference exposure; Thiophene/phenylene co-oligomers; Distributed feedback structure; Gain-narrowing; Laser oscillation;

We have applied field-induced electron spin resonance (FI-ESR) method to organic metal–insulator–semiconductor (MIS) diodes using regioregular poly(3-hexylthiophene) (RR-P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) composites as the active layer, Al2O3 as the gate insulator and gold (Au) or aluminum (Al) as the top electrode. In the case of Al electrode, clear FI-ESR signals are observed with g  ∼ 2.002 and 1.999 for negative and positive gate voltage (V G), respectively, demonstrating that these signals with former and the latter g-values correspond to field-induced positive polarons of RR-P3HT and PCBM radical anions, respectively. Both RR-P3HT and PCBM signals monotonically increase as |V G| increases. The threshold voltages (V th) for field-induced ambipolar charge carriers coincide well with those of capacitance measurements with hysteresis behaviors. On the other hand, in the case of Au electrode, only positive polarons signals are clearly observed and PCBM signals are nearly undetected. These different behaviors of FI-ESR signals between Al and Au top electrodes are discussed in relation to the difference of work functions.
Keywords: Electron spin resonance; Regioregular poly(3-hexylthiophene); PCBM; Metal–insulator–semiconductor (MIS) diodes; Polarons; Bipolarons;

Development of fabrication process for Ag/polydiacetylene (core/shell) hybridized nanocrystals by Takahiro Yokoyama; Akito Masuhara; Tsunenobu Onodera; Hitoshi Kasai; Hidetoshi Oikawa (897-899).
Core/shell hybridized nanocrystals composed of Ag nanoparticle core and polydiacetylene shell were fabricated successfully by means of “co-reprecipitation/microwave irradiation method”. The hybridized nanocrystals were characterized using transmission electron microscopy (TEM) observation and UV–vis absorption spectroscopy. UV–vis spectral measurements revealed that polydiacetylene shell was the red phase while π-conjugated backbone is distorted. Detailed mechanism of formation of the red phase was discussed.
Keywords: Hybridization; Polydiacetylene; Metal nanoparticle;

New π-conjugated pyrimidopyrimidine polymers with two different alkylamino groups at C4 and C8 positions, PPympym(4-NH-n-C8H17-8-NHR) (R =  n-C4H9, n-C6H13, n-C12H25, and n-C16H33), were prepared by dehalogenation polycondensation using nickel zerovalent complex in high yield. The obtained polymers were partly soluble in organic solvents such as chloroform. A chloroform soluble part of PPympym(4-NH-n-C8H17-8-NH-n-C16H33) showed a number-average molecular weight of about 3,000 in GPC analysis. UV–vis spectra of the polymers in CHCl3 showed a π–π* absorption peak at about 450 nm, and the peak position shifted by 30 nm to a longer wavelength in film. The polymers showed photoluminescence both in solution and in film. Cast films of the polymers were electrochemically reduced at about −2.3 V vs. Ag+/Ag. XRD patterns of the polymers revealed the polymers took an end-to-end packed structure.
Keywords: π-Conjugated polymer; Pyrimidopyrimidine; Solid-state structure; Polycondensation;

Reversible transformation and fluorescence modulation in polymorphic crystals of n-butylammonium 2-naphthalenesulfonate by Atsushi Yamamoto; Masaaki Matsumoto; Tomoaki Hinoue; Yuji Mizobe; Ichiro Hisaki; Mikiji Miyata; Norimitsu Tohnai (905-909).
An organic salt composed of 2-naphthalenesulfonic acid and n-butylamine yielded polymorphic crystals: the block-like Form A and the plate-like Form B. The former was obtained from 1-propanol by slow cooling, while the latter was dominantly done from 1,4-dioxane, m-xylene and so on. Interestingly, the former was transformed to the latter by mechanical grinding and the reverse occurred by heat treatment at 120 °C. X-ray crystallographic studies clarified that the former has π–π interactions among naphthalene rings and hydrogen bonding network involving two oxygen atoms of sulfonate group, while the latter has CH–π interactions and the network involving three oxygen atoms. Luminescent properties were different in these crystals and continuously switched with the transformation.
Keywords: Polymorphic transformation; Organic salt; Fluorescence; Mechanical grinding;

Synthesis and solid-state polymerization of a methylene-chain-modified butadiyne derivative by Satoshi Inayama; Tatsumi Kimura; Satoru Shimada; Hiro Matsuda; Shuji Okada (910-913).
5,7-Dodecadiyn-1,12-diyl bis[N-(butoxycarbonylmethyl)carbamate] abbreviated as 4BCMU is one of the typical monomers for solid-state polymerization to form polydiacetylene. In this study, we modified 4BCMU by substituting methylene groups to oxygen atoms. Namely, 3,10-dioxa-5,7-dodecadiyn-1,12-diyl bis[N-(butoxycarbonylmethyl)carbamate] (DO-4BCMU) was synthesized and the replacement effects on the monomer properties were investigated. In powder X-ray diffraction experiments, spacings for the layered structure in 4BCMU and DO-4BCMU crystals were found to be 2.74 nm and 3.56 nm, respectively, and large crystal structural difference was confirmed. The polymer absorption maxima of 4BCMU and DO-4BCMU were observed at 630 nm and 580 nm, respectively. Since conversions of these monomers were similar, butadiyne moieties are aligned in polymerizable stacks and the different spacings seemed to be caused by folding structure differences in substituents. We also prepared mixed crystals of 4BCMU and DO-4BCMU with mixing ratio of 3:7 by melt crystal growth. In this crystal, the layered-structure spacing was 2.31 nm, and their similar molecular structures may be responsive for mixed crystal formation with a new phase. However, it was strangely observed that absorption spectrum of the polymer from the mixed crystals corresponded to summation of the spectra of original polymers from 4BCMU and DO-4BCMU.
Keywords: Polydiacetylene; Solid-state polymerization; Mixed crystal;

Au nano-brush membranes were prepared using a modified template method. Poly(3,4-ethylenedioxythiophene) (PEDOT) films were immobilized by an electropolymerization with the product membrane as the working electrode. The PEDOT film on the nano-brush electrode showed higher electrochromic (EC) coloration compared to the PEDOT film on an Au planar electrode.
Keywords: PEDOT; Au nano-brush electrode; Electropolymerization; Electrochromism; Electronic paper display;

Electrochemical and Raman spectroelectrochemical investigation of single-wall carbon nanotubes–polythiophene hybrid materials by Rafal Pokrop; Irena Kulszewicz-Bajer; Ireneusz Wielgus; Malgorzata Zagorska; David Albertini; Serge Lefrant; Guy Louarn; Adam Pron (919-924).
Two types of polythiophene—single-wall carbon nanotubes (SWCNTs) composites are comparatively studied. Composites of the first type consisted of nonmodified SWCNTs and nonmodified regioregular poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT) or poly(dioctylterthiophenes) (PDOTT). Composites of the second type (molecular composites) were obtained by grafting carboxylic acid functionalized poly(alkylthiophene)s on amine functionalized SWCNTs. In AFM images of the composites of nonfunctionalized components, individual carbon nanotubes can be easily distinguished, which are well dispersed in the polymer matrix showing fibrilar morphology. Cyclic voltammetry and Raman spectroelectrochemical experiments unequivocally show that all characteristic redox and spectroscopic features of both SWCTs and the polymer are retained in the composite material. Moreover the percolating network of SWCTs facilitates the electrochemical doping of the polymeric component. These new, solution processible materials are good candidates for printable contact electrodes in organic electronics. Molecular composites obtained by grafting show a different morphology. It is characterized by a network of fibers of diameters ranging from few dozens to few hundreds nm. Individual composite components cannot be distinguished which is an obvious consequence of the grafting reaction. Combined voltammetric and Raman spectroelectrochemical studies show that the grafting reaction lowers the electrochemical activity of the polymer component and the resulting maximum doping level is, in this case, lower than that found in composites of nonmodified components.
Keywords: Composite; Carbon nanotubes; Polythiophene; Raman spectroscopy; AFM microscopy;

Chiral alkylated poly(m-phenylene)s: Optical activity and thermal stability of helical structures by Risa Sone; Ichiro Takemura; Kenichi Oyaizu; Hiroyuki Nishide (925-930).
Chiral poly[4,6-bis(alkylthio)-1,3-phenylene-alt-2-methyl-1,3-phenylene] was synthesized from 1,3-dibromo-2,6-bis(3-dodecyl-2-methylthio)benzene and 2-methyl-1,3-phenylenebis(pinacol borate) as a precursor of chiral poly(thiaheterohelicene). Circular dichroism (CD) spectra that arise from the poly(1,3-phenylene) backbone inverted according to the chirality of the side chains, which indicated that a helical conformation of the polymer was induced by the interaction between the side chains. The CD intensity of the polymer increased in non-polar solvents such as hexane. The decrease in the molar CD intensity and the broadening of a fluorescence band at higher concentrations suggested that the aggregation of the polymer suppressed the formation of the helical structure. The conformational changes were monitored by the CD and the 1H NMR spectra at different temperatures. In a good solvent such as dichloromethane, the CD intensity increased, and the 1H NMR signal of benzene protons shifted to lower fields at low temperatures. In hexane, the CD spectra and the 1H NMR signals were less dependent on temperatures, as a result of the strong interaction between the chiral alkyl chains in the polymer to freeze the helical conformation.
Keywords: π-Conjugated polymer; Chiral helical induction; Poly(m-phenylene);

Effect of substituent groups on a tetrathiafulvalene (TTF) unit for formation of organic-metal hybrid nanowires was studied. Depend on the substituent groups, the nanowires were obtained as a precipitate just by mixing TTF derivatives and HAuCl4 in CH3CN solution at room temperature via electron transfer reaction between the TTF derivatives and a gold ion. To precede favorably hybrid nanowire formation, increase planarity and introduction of strong interaction on the TTF derivatives are required.
Keywords: Nanomaterials; Nanowires; Tetrathiafulvalene;

Optical and electrical properties and photoexcited laser oscillation of composite film based on π-conjugated polymers by Masahiko Watanabe; Naoyuki Yamasaki; Takashi Nakao; Kimihiro Masuyama; Hitoshi Kubo; Akihiko Fujii; Masanori Ozaki (935-938).
The optical and electrical properties of polymer composite films based on poly(2-methoxy-5-dodecyloxy-p-phenylenevinylene) (MDDOPPV) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) have been studied. The optical properties, such as, absorption and photoluminescence (PL) spectra, PL efficiency, and PL lifetime of the polymer composite films, have been clarified. Utilizing the polymer composite thin film consisting of 50%-F8BT as an emission layer, the multimode lasing from a microcapillary structure with low threshold energy by pulsed photo-pumping and the high current density injection have been demonstrated.
Keywords: Conducting polymer; Poly(p-phenylenevinylene); Poly(9,9-dialkylfluorene); Polymer laser; Microcavity; OLED;

Synthesis of π-conjugated copolymer with dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran unit in the main chain by Koji Nakano; Motonobu Takahashi; Keiko Kawaguchi; Kyoko Nozaki (939-942).
New π-conjugated polymers with dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran (DBBDF) unit in the main chains were synthesized. Copolymerization of 6,12-diiodo-DBBDF with p-diethynylbenzene or 2,7-diethynylfluorene derivative under Sonogashira–Hagiwara coupling-reaction condition gave the corresponding copolymer. The resulting copolymers were soluble in organic solvents such as tetrahydrofuran and chloroform. In UV–vis absorption spectra, both copolymers showed red-shifted spectra compared to their monomer units. In the chloroform solutions, the copolymer with DBBDF and p-diethynylbenzene units showed yellowish-green emission, while the copolymer with DBBDF and 2,7-diethynylfluorene units did greenish-blue emission.
Keywords: π-Conjugated polymer; Heteroacene; Sonogashira–Hagiwara coupling reaction; Copolymerization;

We synthesized poly(meta-phenylene) derivatives with liquid crystalline (LC) groups consisting of phenylcyclohexyl (PCH) or cyanobiphenyl (CB) moiety in the side chains. Thermotropic LC phases and self-assembled structures of the polymers were investigated through polarized optical microscope (POM), differential scanning calorimeter (DSC), and X-ray diffraction (XRD) measurements. The polymers showed discotic liquid crystallinities based on helical structure of the main chains, where the helical chains are self-assembled to form columns along the helical axis. Macroscopic alignments of the polymers were carried out using a magnetic field of 12 T in liquid crystal phases. XRD measurements of the aligned polymers showed that the columns of the main chains are aligned perpendicular to the magnetic field.
Keywords: Conjugated polymers; Poly(meta-phenylene) derivatives; Liquid crystallinity; Discotic column; Helical structure; Self-assembly; Hierarchy;

The synthesis and properties of π-conjugated polymers possessing phenylene-1,4-diyl and 1,3-butadiene-1,4-diyl alternating units in the main chain by reactions of a regioregular organometallic polymer having titanacyclopentadiene-2,5-diyl unit are described. The polymerization of 1,4-diethynyl-2,5-dioctyloxybenzene with a low-valent titanium complex, generated in situ from titanium(IV) isopropoxide and isopropyl magnesium chloride, was carried out at −78 °C to −50 °C for 12 h to give the regioregular organotitanium polymer. The diene-containing π-conjugated polymers were obtained by the reactions of the organotitanium polymer with electrophiles such as hydrochloric acid and iodine. For example, the reaction with hydrochloric acid gave a diene-containing polymer in a 61% yield whose M n and M w/M n were estimated as 5700 and 1.61, respectively (by GPC). The π-conjugated character of the resulting polymer could be supported by its UV–vis spectrum. That is, the absorption maximum (λ max) of the polymer was observable at 470 nm, which was bathochromically shifted by 115 nm compared to that of a model compound (1,4-bis(2-methoxyphenyl)-1,3-butadiene, λ max  = 355 nm).
Keywords: π-Conjugated polymers; Polymer reactions; Reactive polymers; Organometallic polymers; Diene;

Enhanced circularly polarized emission of chiral dimer of π-conjugated perylene in opaque film by Hiroyuki Tsumatori; Takuya Nakashima; Junpei Yuasa; Tsuyoshi Kawai (952-954).
Absorption, CD and circularly polarized luminescence, CPL, of opaque film of a chiral fluorescent perylene derivative are studied. The aggregated state formed in the bulk film is responsible to characteristic optical dissymmetry with enhanced g lum value, which was measured by an originally designed CPL measurement system. The fluorescence emission band characteristic for the aggregated π-stacked structure revealed specific CPL activity at wavelength range longer than that of the isolated molecules.
Keywords: Circularly polarized luminescence; Perylene; π-Conjugated molecule; Chiral aggregates; Self-organized structure;

Orientation of nanowires consisting of poly(3-hexylthiophene) using strong magnetic field by Hiroaki Yonemura; Koichi Yuno; Yuuichi Yamamoto; Sunao Yamada; Yoshihisa Fujiwara; Yoshifumi Tanimoto (955-960).
Nanowires consisting of regioregular poly(3-hexylthiophene) (P3HT) as a conducting polymer were prepared using p-xylene. Magnetic processing of the nanowires was carried out using two superconducting magnets with horizontal (B max  = 8 T) and vertical (B max  = 10 T) directions. The formation of the nanowires was confirmed by atomic force microscopy (AFM) measurement. The results from the AFM images and the polarized absorption spectra on glass plates indicated that the nanowires partly oriented themselves with their long axes, which are parallel to the π–π stacking direction, being perpendicular to the magnetic field. The magnetic orientation is most likely ascribed to anisotropy in the magnetic susceptibilities of the ordered P3HT in the nanowires.
Keywords: Magnetic orientation; Nanowire; Poly(3-hexylthiophene); Polarized absorption spectrum; Magnetic force;

Memory mechanism of printable ferroelectric TFT memory with tertiary structured polypeptide as a dielectric layer by Masatoshi Hasegawa; Norihisa Kobayashi; Sei Uemura; Toshihide Kamata (961-964).
Printable nonvolatile memory devices have been attracting considerable interest because of their application to flexible large-area devices. In order to fabricate such memory devices, it is necessary to discover a new ferroelectric material and to develop an efficient process for its preparation. We have previously reported that poly(γ-methyl-L-glutamate) (PMLG) functions as a ferroelectric layer of an organic thin-film transistor (OTFT) memory device [S. Uemura, A. Komukai, R. Sakaida, M. Yoshida, S. Hoshino, T. Kodzasa, T. Kamata, Synth. Met. 153 (2005) 405]. Further, ferroelectricity is observed when α-helical PMLG molecules are aligned in a direction parallel to the film surface. In this study, we investigate the effect of the tertiary structure of PMLG molecules on the hysteresis of OTFT memory devices, i.e., memory performance. From the results, we conclude that the hysteresis of the OTFT is strongly affected by the helical tertiary structure of PMLG molecules, similar to the structure of a cholesteric liquid crystal phase.
Keywords: Printable device; Flexible device; Organic memory; Biopolymer; Organic transistor;

Photocurrent generation properties of electrochemically polymerized terthiophene-linked fullerene film by Tsuyoshi Akiyama; Toshihide Fukuyama; Kosuke Sugawa; Hiroyuki Yoneda; Sunao Yamada (965-968).
Terthiophene derivative of C60 fullerene was synthesized. The polymerized film of this fullerene analog was prepared on an indium–tin-oxide electrode by electrochemical polymerization at +1.4 V versus a Ag wire. The absorbance of the polymerized film was increased by increasing the electrochemical polymerization time. The polymerized film generated stable photocurrents in the presence of triethanolamine. Optimization of the amount of adsorbed polymerized film for improving the photoelectric conversion performance was achieved by controlling the polymerization time.
Keywords: Fullerene; Polythiophene; Photocurrent; Electrochemical polymerization; Photoinduced electron transfer;

Mesomorphic and polymerization behaviors of 4-(icosa-1,3-diynyl)benzoic acid by Satoshi Dei; Tomoyo Shimogaki; Akikazu Matsumoto (969-972).
We report the mesomorphic property of 4-(icosa-1,3-diynyl)benzoic acid (16,Ph-DA-CO2H) as a new type of liquid-crystalline 4-carboxyphenyl-substituted diacetylene monomer based on the results obtained by differential scanning calorimetric (DSC), wide-angle X-ray diffraction (XRD), and polarized optical microscopic (POM) measurements. The polymerization of 16,Ph-DA-CO2H was also carried out in the isotropic and liquid-crystalline states with or without UV irradiation.
Keywords: Conjugated polymer; Polydiacetylene; Liquid crystal; Radical polymerization;

Electrical bistability of composite film comprising hyper-branched polymer and gold nanoparticle by Hisashi Ichikawa; Kei Yasui; Masaaki Ozawa; Katsuhiko Fujita (973-976).
A hyper-branched polymer (HPS) with dithiocarbamate (DC) end groups and gold nanoparticle stabilized by HPS (HPSAu) were synthesized. We fabricated a single-layered organic electrical bistable device (OBD). It exhibited a unipolar switching behavior with a negative differential resistance (NDR). When a certain voltage was applied to the pristine state, the device changed irreversibly and began exhibiting bistable conductive states; the equivalent circuit of this device is a parallel circuit comprising one resistance and one capacitor.
Keywords: Organic bistable device; Organic memory; Electrical bistability; Nanoparticle; Hyper-branched polymers;

Supramolecular assemblies of oligothiophene derivatives bearing β-cyclodextrin by Kazuya Sakamoto; Yoshinori Takashima; Hiroyasu Yamaguchi; Akira Harada (977-981).
2T-βCD2 and 3T-βCD2, which have bithiophene (2T) and terthiophene (3T) with β-cyclodextrin (CD) at each end form supramolecular assemblies in aqueous solutions. These supramolecular assemblies were characterized by NMR, UV, fluorescence spectroscopy, circular dichroism spectroscopy, and atomic force microscope (AFM). Supramolecular assemblies from 3T-βCD2 form orientated structures due to their π–π stacking ability. AFM images of the supramolecular assembly incorporating 3T-βCD2 showed fibrous objects on mica substrates.
Keywords: Supramolecular assembly; Oligothiophene; Cyclodextrin;

Novel helical platinum-acetylide polymers with high molecular weights were prepared by reacting 3,3′-diethynyl-2,2′-dialkoxy-1,1′-binaphthyl with Pt(PBu3)2Cl2 in the presence of a CuCl catalyst. The helical structure was confirmed by large specific rotation and large Cotton effect due to the MLCT band characteristic of the platinum-acetylide complex, compared to the corresponding diplatinum model complexes.
Keywords: Organometallic polymer; Platinum; Acetylide; Helix; Chiral polymer;

Effects of casting solvents on characteristics of organic EL devices containing poly(l-glutamate) as hole-transport material by Toshihiro Hiejima; Yosuke Takamizawa; Yoshinori Tanaka; Kenji Ueda; Takayuki Uchida (986-989).
The characteristics of EL devices containing α-helical poly(l-glutamate) and having a carbazole side chain (PCELG) were found to strongly depend on the casting solvents. Among EL devices fabricated using chlorine-containing casting solvents such as 1,2-dichloroethane (DCE), 1,1,2,2-tetrachloroethane (TCE), chloroform (CHCl3), and monochlorobenzene (ϕ-Cl), the EL device fabricated using the DCE solvent exhibited the maximum luminance (65.8 cd/m2). The difference between the threshold voltages of the devices ranged up to 6.0 V, despite their fabrication by using solutions with the same composition ratio. The maximal efficiency of the devices fabricated using the DCE solvent was found to be 20 times greater than that of the devices fabricated using TCE solvents. A comparison of the current densities and voltages among devices fabricated using different casting solvents at their maximal efficiencies showed that the maximal efficiencies tended to significantly increase in the order TCE < CHCl3  < DCE solvents at similar voltages (∼15 V), despite a lowering of the current density. The current density was considered to be directly related to the number of carriers injected into the device. The above-mentioned observations suggested that the maximal efficiency in these devices was not the hole and electron injection efficiencies, but the values of some parameters subsequent to carrier injection, such as the recombination rate, amount of excitons generated, and the diffusion length.
Keywords: Organic EL device; Poly(l-glutamate); Hole transport material; Helix conformation; Recombination rate; Exciton diffusion;