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2000The syntheses of two novel iptycene monomers, 1,4-diiodotriptycene (I) and 2,3-diiodo-4,9-dihydro-4,9-benzonaphtho[2,3,c]thiophene (II), are described herein. These monomers were subsequently copolymd. with a no. of diethynylphenyl monomers via a Sonogashira-Hagihara coupling to afford both regiodefined polymers and random terpolymers. Terpolymers derived from coupling I and 2,5-dihexadecyloxy1,1,4-diiodobenzene with a diethynylpentiptycene exhibit emission spectra that are only slightly perturbed from soln. to the solid state, suggesting that polymer assocn. is effectively inhibited in condensed phases. An äll-iptycene” polymer derived from the copolymn. of II with a diethynylpentiptycene monomer is also notable in that it owes its soly. to a combination of its nonlinearity and the presence of rigid iptycene groups rather than to flexible side chains. [on SciFinder(R)]
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2000
Induced Antiferroelectric Smectic-C*A Phase by Doping Ferroelectric-C* Phase with Bent-Shaped Molecules.
Physical Review Letters,vol.85,p.2526–2529,2000Doping of the ferroelec. Sm-C* phase with bent-shaped mols. induces the antiferroelec. Sm-C*A phase. The effect was obsd. by electrooptic and dielec. measurements in systems with weak interlayer interactions in which the relative strength of anticlinic-synclinic order between mols. in adjacent layers is easily controlled by external factors. FTIR spectroscopy studies suggest that the bent-shaped mols. are not flat. They reorient upon the elec. field-induced antiferroelec.-ferroelec. transition to adopt a position in which the av. direction of the carbonyl groups is in the smectic plane and a bending tip along the C2 symmetry axis. [on SciFinder(R)] -
2000
Controlling conjugated polymer photophysics: role of interchain spacing within two-dimensional assemblies.
Polymeric Materials Science and Engineering,vol.83,p.529–530,2000Prepn. and photophys. characterization of three polydiacetylene derivs. are discussed with the emphasis on the role of interchain spacing within two-dimensional Langmuir monolayer assemblies. Photophys. and geometrical properties and normalized UV visible and photoluminescence of these films are also discussed. [on SciFinder(R)] -
2000
Toward new actuating devices: synthesis and electrochemical studies of poly(11,23-bis([2,2′-bithiophen]-5-yl)-26,28-dimethoxycalix[4]arene-25,27-diol).
Polymeric Materials Science and Engineering,vol.83,p.523–524,2000The prepn. and cond. measurements of the title polymer were discussed. The cond. studies showed a large hysteresis suggesting that a mol. level compression took place. Thus the materials based on this polymer should have potential use in actuating devices or as artificial muscle. [on SciFinder(R)] -
1999
Handbook of liquid crystals. (4-volume set.) Edited by D. Demus, J. Goodby, G. W. Gray, H. W. Spiess and B. Vill.
Angewandte Chemie, International Edition,vol.38,p.2279–2281,1999 -
1999
Polarity- and voltage-controlled color-variable light-emitting devices based on conjugated polymers.
Applied Physics Letters,vol.74,p.2593–2595,1999Voltage- and polarity-controlled multilayer multicolor light-emitting test devices based on pyridine-contg. conjugated polymers and derivs. of polyacetylene were fabricated and evaluated. The polymer blends of poly(pyridyl vinylene deriv.) and poly(bis(hexadecyloxy)phenylene-vinylene) and poly(di-Ph Bu acetylene) or poly(hexyl Ph acetylene) are used as the emitting material. Sulfonated poly(o-methoxyaniline) is the redox layer and ITO and Al were used as electrodes. The devices emit red light under forward bias and multiple colors of light (from orange-red to green) under reverse bias. The colors under reverse bias are controlled by the magnitude of the applied voltages. [on SciFinder(R)] -
1999
Nematic Liquid Crystals with Bent-Rod Shapes: Mesomorphic Thiophenes with Lateral Dipole Moments.
Chemistry of Materials,vol.11,p.867–871,1999A no. of bent-rod mols. of thiophene derivs. were prepd., and their phase behavior was studied. Mostly these compds. have the nematic phase. The crystal structure of 3,4-dicyano-2,5-bis[(methoxyphenyl)ethynyl]thiophene shows that the antiparallel arrangements of lateral dipoles seems most likely. Crystals are monoclinic, space group P21/n, with a 11.5757(2), b 10.03300(10), c 17.3438(4) AA, $beta$ 100.4580(10)°; Z = -
1999
Eight-Vertex Metallomesogens: Zirconium Tetrakis-$beta$-diketonate Liquid Crystals.
Chemistry of Materials,vol.11,p.130–134,1999Square antiprism Zr tetrakis-$beta$-diketonate complexes with 24 alkoxy chains organize in columnar liq. crystal phases. X-ray diffraction and polarized microscopy studies on complexes with n-alkoxy side chains revealed a columnar hexagonal phase. These sandwich-shaped compds. have much lower transition temps. than their discotic analogs, which leads to the desirable attribute of room temp. liq. crystallinity. The addn. of two branching Me groups to the alkoxy chains dramatically alters the properties of these materials. The branched side chain analogs exhibited a higher clearing point while the liq. crystallinity is maintained at room temp. The branching Me groups also induced a bulk reorganization of the material to a rare columnar oblique phase (Colob). [on SciFinder(R)] -
1999
Conducting redox polymers: investigations of polythiophene-Ru(bpy)3n+ hybrid materials.
Journal of Materials Chemistry,vol.9,p.2123–2131,1999A series of thiophene-appended RuII(bpy)3 derivs., Ru(1)3, Ru(2)3, Ru(3)3, Ru(bpy)2(1), Ru(bpy)2(2), and their resulting polymers were synthesized and characterized. The bpy ligands 5,5′-bis(5-(2,2′-bithienyl))-2,2′-bipyridine (1), 4,4′-bis(5-(2,2′-bithienyl))-2,2′-bipyridine (2), and 4-(5-(2,2′-bithienyl))-2,2′-bipyridine (3), all contain electrochem. polymerizable bithienyl moieties. The monomers Ru(2)3, Ru(3)3, Ru(bpy)2(1) and Ru(bpy)2(2) display spectroscopic features that are similar to the ligand-based and MLCT [metal-to-ligand charge-transfer] bands found for Ru(bpy)3. The cyclic voltammograms of all of these polymers display both metal-centered and thiophene-based electroactivity. High redox cond. was found in poly(Ru(2)3) and poly(Ru(3)3) for both the thiophene-based oxidn. and metal-based redn. processes. These results indicate that the polymers display charge localization for both the metal complexes and the tetrathienyl connecting units. The degree of interconnection (no. of linkages) and the substitution pattern were found to control the cond. of these polymers. The highest cond. (3.3 × 10-3 S cm-1) was found for poly(Ru(2)3), which is able to have up to 6 linkages with other ruthenium complexes and possessing a 4,4′-substitution pattern that allows effective orbital overlap of the conjugated polymer backbone with the ruthenium centers. [on SciFinder(R)] -
1999
Pyrylium Salts via Electrophilic Cyclization: Applications for Novel 3-Arylisoquinoline Syntheses.
Journal of Organic Chemistry,vol.64,p.6499–6504,1999O-Ethynylphenylcarbonyl compds. undergo cyclization to 2-benzopyrylium salts on treatment with acid. Treatment of these compds. with NH3 gave isoquinolines. 1-Ethoxy-2-benzopyrylium salts were partially hydrolyzed to the hydroxy analogs and 1-dimethylaminoisoquinolines were accompanied by the amino analogs. [on SciFinder(R)] -
1999
Polythiophene Hybrids of Transition-Metal Bis(salicylidenimine)s: Correlation between Structure and Electronic Properties.
Journal of the American Chemical Society,vol.121,p.8825–8834,1999The synthesis, electrochem., and spectroscopic behavior of tetradentate bis(salicylidenimine) transition metal complexes are reported. Appending these complexes with 3,4-ethylenedioxythiophene (EDOT) moieties allows for electrochem. polymn. at much lower potentials than the parent SALEN complexes. The resulting polymers display well-defined org.-based electrochem. at potentials <0.5 V vs. Fc/Fc+. The EDOT-modified N,N'-ethylene bis(salicylidene), N,N'-o-phenylene bis(salicylidene), and N,N'-trans-cyclohexylene bis(salicylidene) complexes I and II, III and IV, and V and VI, resp., display cyclic voltammograms with four org.-based redox waves. Increasing the interchain sepn. through the use of nonplanar bis(salicylidene) ligands results in only two redox waves. The cond. of the copper-based polymers decreases with increasing interchain spacing, with the max. cond. being 92 S cm-1 for poly(I) and 16 S cm-1 for the stilbenediamine complex polymer. The nickel complexes were less sensitive to increased interchain sepn. and showed cond. greater than 48 S cm-1 regardless of interchain spacing and near 100 S cm-1 in the case of poly(IV). In situ spectroelectrochem. was consistent with the segmented electronic nature of these polymers. Cyclic voltammetry of an analogous uranyl complex revealed that two electrons per repeat unit were removed during oxidn. From electrochem. and in situ EPR spectroscopic studies suggest that $π$-aggregation processes take place in those polymers in which close interchain spacing is allowed. [on SciFinder(R)] -
1999
Cooperative Chirality in Columnar Liquid Crystals: Studies of Fluxional Octahedral Metallomesogens.
Journal of the American Chemical Society,vol.121,p.4518–4519,1999Liq. crystals displaying a Colh (columnar hexagonal) phase can display a cooperative chiral state. In the authors model the hexagonal symmetry is an integral feature that favors the chiral state. This latter point is also supported by the recent work on fluxional 8 vertex Zr4+ mesogens (Trazaska et al. 1999) with the same ligands as used in this paper, wherein no increase was found in the CD signal on cooling from the isotropic phase into the oblique columnar phase. [on SciFinder(R)] -
1999
Energy Migration in a Poly(phenylene ethynylene): Determination of Interpolymer Transport in Anisotropic Langmuir-Blodgett Films.
Journal of the American Chemical Society,vol.121,p.1466–1472,1999The photophys. and energy transport properties of poly(p-phenylene ethynylene) were studied in thin films. Highly aligned films of a precise thickness, prepd. by sequential monolayer deposition using the Langmuir-Blodgett technique, were surface modified with luminescent traps (Acridine Orange, AO) for energy transfer studies. The degree of energy transfer to the traps was studied as a function of the AO concn. and the no. of polymer layers. An increased efficiency of energy transfer to the traps was obsd. with increasing nos. of layers to an approx. thickness of 16 layers. This behavior is consistent with a transition to a three-dimensional energy migration topol. A phenomenol. model for the transport was proposed, and solns. were obtained by numerical methods. The model yields a fast (>6 × 1011 s-1) rate of energy transfer between polymer layers and a diffusion length of more than 100 \AA in the Z direction (normal to the film surface). [on SciFinder(R)] -
1999
Nanoscale Fibrils and Grids: Aggregated Structures from Rigid-Rod Conjugated Polymers.
Macromolecules,vol.32,p.1500–1507,1999Langmuir-Blodgett (LB) mol. processing of conjugated polymers [poly(phenylene ethynylenes)] into highly aligned films has revealed conditions for the formation of liq. cryst. monolayer films that structurally evolve into fibril aggregates. The structural requirements for poly(phenylene ethynylene)s to display liq. cryst. phases capable or alignment by LB methods were detd. The reconstruction of monolayers into fibril structures requires a low glass-transition temp. (Tg), weak surface anchoring, and a monolayer with a high energy that can be stabilized by reorganization. This assembly of polymers into aggregated structures produces rigid structural units analogous to naturally occurring fibrous proteins such as collagen and elastin. These oriented, shape-persistent nanoscale structures create new possibilities for the construction of complex supramol. structures, and this capability was demonstrated by the formation of a nanoscale grid. [on SciFinder(R)] -
1999
Synthesis and characterization of liquid crystalline triaryloxy-s-triazines.
Molecular Crystals and Liquid Crystals Science and Technology, Section A: Molecular Crystals and Liquid Crystals,vol.326,p.113–138,19992,4,6-Tris[p-(p’-n-alkylphenyliminomethylene)phenoxy]-s-triazines (3) are calamitic liq. crystals based on x-ray diffraction patterns, optical textures, and mol. modeling results. Replacement of the Schiff’s base moieties in the mesogenic arms to form 2,4,6-tris(p-n-octyloxycarbonylphenoxy)-s-triazine (7) did not result in a liq. cryst. compd. The tricarbonate 2,4,6-tris(p-cholesteryloxycarbonyloxyphenoxy)-s-triazine (11) is liq. cryst. based on the optical textures obsd., although the mesophase type could not be detd. due to the high melting transition and thermal instability of this compd. The use of six ester groups around the triazine nucleus, as 2,4,6-tris(3,5-dicarboalkoxyphenoxy)-s-triazines (13), resulted in compds. which displayed normal melting behavior and no detectable mesomorphism. [on SciFinder(R)] -
1999A review with 11 refs. is given on the authors’ work with emphasis on fluorescence-based sensor schemes and new chemoresistive transducer mechanisms. [on SciFinder(R)]
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1999
Transition metals in polymeric $π$-conjugated organic frameworks.
Progress in Inorganic Chemistry,vol.48,p.123–231,1999A review with 356 refs. on the wide variety of transition metal-centered conjugated/conducting polymers and networks. Organometallic-based systems, such as organometallic acetylenic polymers, metallacycle polymers, polyferrocenylenes, transition metal aryl complexes, pendant organometallic polymers, pendant ferrocene polymers, organometallic coordination polymers, as well as various types of coordination complexes, such as one-dimensional and two-dimensional phthalocyanine polymers, conjugated porphyrin polymers, polymers derived from schiff-base complexes, polymeric bipyridine and related complexes, and diisocyanoaryl ligands are described. [on SciFinder(R)] -
1999
Full color LEDs with parahexaphenyl and polypyridine based copolymer.
Synthetic Metals,vol.102,p.1085–1086,1999Results are presented of luminescence (PL) and electroluminescence (EL) studies on color variable LEDs based on parahexaphenyl (PHP) and polypyridine (PPy) related polymers and copolymers. In the fabricated bilayer and 3 layer heterostructure EL devices, PPy and poly(pyridyl vinylene phenylene vinylene) (PPyVPV) are used as electron and hole transport layers resp. For ITO/PPyVPV/PHP/PPy/Al EL device, multi-colors emission in the wide range of the visible spectrum from blue (425 nm) to green (530 nm) and near IR (700 nm) were obtained. The optical and elec. characteristics of bilayer and multilayer EL devices are presented and discussed. [on SciFinder(R)] -
1999
Color variable multilayer light emitting devices based on conjugated polymers and oligomers.
Synthetic Metals,vol.102,p.889–892,1999The authors report the fabrication and study of color variable multilayer light emitting devices based on pyridine-contg. conjugated polymers and para-sexiphenyl (6P) oligomer. Polarity controlled two color devices were fabricated by sandwiching the emitting layer in between emeraldine base and sulfonated forms of polyaniline (SPAN). The emitting layer typically is a blend of two polymers, one of which is a pyridine-based copolymer (PPyVPV). The devices can be operated under either polarity of driving voltage with different colors of light being emitted from different locations. Under forward bias, red light is generated from PPyVPV/SPAN interface. Under reverse bias, light is generated from the bulk of the emitting layer whose color is dependent on the materials used. Voltage controlled multicolor devices were fabricated by combining the pyridine-based polymers with the 6P oligomer. Voltage dependent multicolor emission was obsd. in both bilayer and trilayer devices. The emission colors of single devices cover a wide range of visible spectra whose CIE color coordinates vary from blue to white to green with increasing voltages. [on SciFinder(R)] -
1998
The Molecular Wire Approach to Sensory Signal Amplification.
Accounts of Chemical Research,vol.31,p.201–207,1998A review, with 24 refs., is given on conceptual aspects of how mol. wires (conjugated polymers) can be used to amplify mol. chemosensors. The properties that are responsible are universal and can be utilized in a multitude of schemes. The sensitivity and diversity available suggest that these materials will be important for future sensor technologies. [on SciFinder(R)]
