Synthetic Metals (v.158, #1-2)

Conducting nylon, cotton and wool yarns by continuous vapor polymerization of pyrrole by Akif Kaynak; Saeed Shaikhzadeh Najar; Richard C. Foitzik (1-5).
Conductive textile yarns were prepared by a continuous vapor polymerization method; the application of polypyrrole by the continuous vapor polymerization method used is designed for the easy adaptation into industrial procedures. The resultant conductive yarns were examined by longitudinal and cross-sectional views, clearly showing the varying levels of penetration of the polymer into the yarn structure. It was found that for wool the optimum specific resistance was achieved by using the 400 TPM yarn with a FeCl3 solution concentration of 80 g/L FeCl3 to produce 1.69 Ω g/cm2. For cotton yarn, the optimum specific resistance of 1.53 Ω g/cm2 was obtained with 80 g/L of a FeCl3 solution.
Keywords: Polypyrrole; Conductive textiles; Continuous vapor-phase polymerization; Nylon; Wool; Cotton;

Electrosynthesis of poly(2-methyl-thieno[3,2-b]benzothiophene) [poly(2-MeTBT)] and poly(3-methyl-thieno[3,2-b]benzothiophene) [poly(3-MeTBT)], was performed by anodic oxidation of 2-MeTBT and 3-MeTBT on Pt electrode in 0.1 M LiClO4 acetonitrile solution and in a partially aqueous micellar medium (water/methanol, 9/91, v/v) containing 0.39 M perchloric acid and 0.1 M SDS (sodium dodecylsulfate). The electrochemical characteristics and FT-IR spectra of 2-MeTBT and 3-MeTBT, as well as their optical properties were studied. The corresponding polymers were investigated by cyclic voltammetry, MALDI-TOF, FT-IR, electronic absorption and fluorescence spectroscopy. A theoretical approach based on molecular orbital (MO) calculations and using a radical-cation electropolymerisation mechanism, was proposed for the oligomer structural characterization.
Keywords: 2-Methyl- and 3-methyl-thieno[3,2-b]benzothiophene; Electropolymerization; Conducting oligomers; Optical properties; Micellar media;

Electron mobility and electroluminescence efficiency of blue conjugated polymers by Chia-Ming Yang; Hua-Hsien Liao; Sheng-Fu Horng; Hsin-Fei Meng; Shin-Rong Tseng; Chain-Shu Hsu (25-28).
We study systematically the underlying property which determines the electroluminescence efficiency of blue polymers based on polyfluorene and its copolymers. The photoluminescence efficiency is high (40–50%) for all the selected polymers, but the electroluminescence efficiency varies in a wide range. The hole mobility is measured by transient electroluminescence. The electron mobility is obtained from the current in electron-only device using space-charge-limited current equation. All polymers share roughly the same results, whereas electron mobility is the critical factor for electroluminescence. In general, low efficiency results from the low electron mobility.
Keywords: Polymer-LED; PFO(poly-fluorene); TR-EL; Electron mobility;

A polyaniline/WO3 nanofiber composite-based ZnO/64° YX LiNbO3 SAW hydrogen gas sensor by A.Z. Sadek; W. Wlodarski; K. Shin; R.B. Kaner; K. Kalantar-zadeh (29-32).
Polyaniline/WO3 nanofiber composite-based surface acoustic wave (SAW) gas sensor has been investigated towards hydrogen (H2). Chemical oxidative polymerization of aniline was employed to synthesize polyaniline nanofibers with WO3 nanoparticles. The nanocomposite was deposited onto a layered ZnO/64° YX LiNbO3 SAW transducer. The sensor was exposed to various concentrations of H2 gas and operated at room temperature. The sensor response was found to be 7 kHz towards 1% of H2 in synthetic air. A fast response and recovery with good repeatability in a stable baseline condition were observed at room temperature.
Keywords: Polyaniline nanofiber; WO3; Nanocomposite; Gas sensor; H2;

Synthesis, characterization and redox behavior of nickel(II) and cobalt(II) polymeric complexes by Chaofan Zhong; Aihong He; Rongfang Guo; Qian Wu; Hualiang Huang (33-37).
Synthesis route: Two ligands 4,4′-bis[2- (2′-pyridyl)benzimidazolyl]biphenyl (Bmbp) and 1,3,5-tris[2-(2′-pyridyl)benzimidazolyl]benzene (Tmb), were synthesized by Ullmann condensation. Polymeric complexes were synthesized by Ni(II), Co(II) with Bmbp and Tmb, respectively.▪The polymeric complexes of 4,4′-bis[2-(2′-pyridyl)benzimidazolyl]biphenyl (Bmbp) with Co(II) (1), Ni(II) (2) and 1,3,5-tris[2-(2′-pyridyl)benzimidazolyl]benzene (Tmb) with Co(II) (3), Ni(II) (4) were successfully synthesized and characterized by using IR spectroscopy, elemental analysis, and gel permeation chromatography (GPC) analysis. Their cyclic voltametric behavior and thermal property were also studied. The results indicated these complexes display an irreversible redox process and have high thermal stability.
Keywords: Polymeric complexes; Electrochemical property; Co(II); Ni(II);

The effect of monomer and electrolyte concentrations during synthesis on the actuation of PPy(CF3SO3) films in aqueous electrolytes by Shu Yi Chu; Paul A. Kilmartin; Sui Jing; Graham A. Bowmaker; Ralph P. Cooney; Jadranka Travas-Sejdic (38-44).
Free-standing films of polypyrrole, PPy(CF3SO3), were electropolymerised galvanostatically from propylene carbonate solutions containing tetrabutylammonium trifluoromethanesulfonate of a range of pyrrole or electrolyte concentrations. The electrochemomechanical deformation (ECMD), measured in situ during cyclic voltammetry experiments, was found to increase when a higher concentration of pyrrole monomer or CF3SO3 electrolyte was used during the polymerisation. X-ray photoelectron spectroscopy was used to estimate the presence of different forms of carbon in the PPy(CF3SO3) films, including the α and β carbons of the pyrrole ring, the ‘disordered carbon’ and carbonyl carbon. These XPS results were correlated with the strains observed in ECMD measurements and the doping level estimated from N1s XPS spectra. The morphology of the films obtained for different growth conditions was also investigated by means of SEM.
Keywords: Polypyrrole; Actuator; Electropolymerisation; Strain;

Photoelectron spectroscopic studies of ultra-thin CuPc and PTCDA layers on Cu(1 0 0) by M. Andreasson; M. Tengelin-Nilsson; L. Ilver; J. Kanski (45-49).
The initial interaction and interface formation between Cu(1 0 0) and the organic semiconductors 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) and copper phtalocyanine (CuPc) has been studied by means of angle-resolved UV photoelectron spectroscopy (ARUPS). Both CuPc and PTCDA are known to adsorb strongly on the Cu(1 0 0) surface. The bonding interaction is revealed via interface-related structures in photoemission spectra. However, the spectra develop rather differently in the low coverage regime: while CuPc molecular states are observed below monolayer coverage, the first PTCDA layer is found to be reacted such that the adsorbate-induced emission is strongly modified relative that of intact PTCDA molecules. We find a number of structures that are neither PTCDA- nor Cu-derived, and that the oxygen-related component of the PTCDA spectrum is completely missing in spectra from the monolayer. Importantly for device applications, we find evidence of interfacial electronic states in the form of new peaks located in the former HOMO–LUMO gap for both molecules. In the case of PTCDA these support a chemisorptive bonding model, whereas in the case of CuPc we interpret the state as a monolayer-specific resonance.
Keywords: CuPc; PTCDA; Photoemission; Interface states;

A number of terthiophene derivatives have been synthesized by standard chemical procedures in order to measure the electrical properties of their micro-crystalline powders by impedance spectroscopy, in this case the complex admittance versus frequency. The compounds studied were T3, BrT3, Br2T3, T3NO2, BrT3NO2, IT3NO2, and Br-terminated polythiophene. The substituents were all α-position or α,α′-position terminations. The sample powders were placed between a co-axial tube capacitor arrangement and connected to a standard impedance bridge with a frequency range of 20 Hz to 1 MHz. The conductivity showed a simple power law dependence on the frequency with the exponent giving a good indication of the change in conjugation length due to the substituted end group. The push–pull nature of BrT3NO2 and IT3NO2 were clearly seen by the enhancement of both conductivity and susceptibility. The polythiophene sample was significantly more conducting and had a much higher susceptibility. It was observed to undergo a color change, from red to silver, when subjected to shear stress. This was accompanied by an increased conductivity most likely due to an enhancement of π-bond stacking between molecules. The technique presented is a useful and quick way to analyze the potential of new organic semiconductors.
Keywords: Terthiophene; Polythiophene; Conductivity; Susceptibility;

Polyaniline (PANI) nanofibers were prepared via a novel interfacial polymerization method. In this method, aniline dissolved in xylene that is immiscible to water was directly added into the aqueous solution of the oxidant under stirring. The polymerization was carried out at the interface formed between the organic liquid drops and the water. The morphology, structure and water-dispersity of the samples prepared under different conditions were investigated by the aid of TEM, SEM, FT-IR and UV–vis spectra. The conductivity of the samples was also measured through typical four-probe technique.
Keywords: Polyaniline; Nanofibers; Interfacial polymerization;

Two novel near-infrared absorbing perylene imide derivatives (I and II) with benzo[e]indole were designed and synthesized as sensitizers for dye-sensitized solar cells (DSSCs), and their structures were characterized by 1H NMR, 13C NMR, FT-IR, UV–vis, MS-ESI spectra, etc. The absorption spectra, electrochemical and photovoltatic properties of I and II were extensively investigated. Two perylene dyes have wide absorption bands with high molar extinction coefficients over the entire visible spectrum. Electrochemical properties indicated that the electron injection process from the excited dye molecule to TiO2 conduction band was energetically permitted. However, the preliminary photophysical and photoelectrochemical measurements show that the two perylene dyes have lower overall conversion efficiency on DSSCs application, although they have broad and intense absorption spectra in the visible region (up to 800 nm). This may be that the perylene imide group, which contains strong electron-withdrawing nature has effect on the polarity of the whole molecule, resulting in the unbeneficial transferring direction of photo-generated electrons, which decreases the overall photocurrent performance.
Keywords: Perylene imide derivatives; Dye-sensitized solar cell; Photovoltaic properties;

We comment on both flow behavior (shear stress vs. shear rate) and universal yield stress equation of electrorheological (ER) suspensions of recently reported conducting polypyrrole (PPy)-coated polyethylene (PE) under applied electric strengths. Our proposed Cho-Choi-Jhon (CCJ) shear stress model not only fits flow curves for the PPy-coated PE ER fluid, but also provides a better explanation on their flow properties compared to De Kee–Turcotte model. Moreover, using the deduced critical electric field strength and additional scaled parameter, we find that the universal yield stress equation proposed collapses the data of double-coated PE onto a single curve.
Keywords: Electrorheological fluid; Yield stress; Polypyrrole;