Synthesis and electrical properties of poly[2-(2-(4-trifluoromethyl)phenyl)ethenyl-1,4-phenylenevinylene] and PPV copolymers

Summary Poly[2-(2-(4-(trifluoromethyl)phenyl)ethenyl)-5-methoxy-1,4-phenylenevinylene] (PFEMPV) and a series of PPV copolymers containing 1,4-phenylenevinylene (PV) units were synthesized through a water-soluble precursor route, and their electrical and third-order nonlinear optical properties were studied. The PFEMPV films could not be doped with I₂, but FeCl₃-doped films showed an electrical conductivity of 5.0x10^-4 S/cm. The conductivities of FeCl₃-doped copolymer films ranged from 2.0x10^-3 to 2.0 S/cm depending on their copolymer compositions. The third-order nonlinear optical susceptibility, ⁽³⁾(–;,,–), was also investigated by the degenerate four wave mixing technique at 602 nm. The ⁽³⁾ value of PFEMPV was 6.9x10^-11 esu. The photoluminescence spectrum of PFEMPV shows its emission maximum at 550 nm.     

Soluble polystyrenes with pyrrole pendant groups and their electroactive properties

Summary Four soluble styrenic polymers containing 3-substituted pendant pyrrole rings with ester or amide arm spacer were synthesized. Their electroactive characteristics were investigated by cyclic voltammetry. The chemical oxidation was accomplished by adding FeCl₃ into a solution of styrenic polymers dissolved in 1:1 mixture of dimethylformamide (DMF) and acetonitrile (ACN). The electrical conductivities of the chemically oxidized black powder of the styrenic polymers were in the range of 10^-1010^-9 S/cm.     

High-conductivity solid copper ion conductors: the sulphonium halide-copper(I) halide systems

The electrical conductivities of the copper (I) halide-sulphonium halide systems were measured and high conductivity copper ion conductors were found in the copper (I) iodide-1-methyl-1-thioniacyclohexane iodide (C₅H₁₀SCH₃I) and copper (I) iodide-4-methyl-1, 4-oxathianium iodide (C₄H₈OSCH₃I) systems. The dependence of electrical conductivity on the composition showed that the maximum conductivity appeared at 83.4 mol% CuI for these two systems. The highest conductivities of the systems, CuI-C₅H₁₀SCH₃I and CuI-C₄H₈OSCH₃I, were 1.4×10^–3 and 7.2×10^–4 ( cm)^–1 at 25 C, respectively. The conduction in these systems was essentially ionic.     

Birefringence and orientation parameters of cold‐drawn viscose fibers

This study was carried out by two beam polarizing interference Pluta microscope to obtain changes undrawn viscose fibers. Application of the appropriate mathematical equations indicates that the refractive indices in the direction of the drawing force increase with increasing the draw ratio and decrease in the perpendicular direction. The changes in the draw ratio were evaluated to obtain the shrinkage stress, the mechanical function factors 〈P₂(cos θ)〉 and 〈P₄(cos θ)〉, the average work per chain W′ for a collection of chains, and the average mechanical orientation. The optical results were to obtain the three optical orientation functions, the dielectric constant and the dielectric susceptibility and the average orientation function. Also calculation of the intrinsic crystalline and amorphous birefringence. Evaluation of another opto‐mechanical parameters were given, too. An empirical formula was suggested to evaluate the relationship between the draw ratio and some determined opto mechanical parameters. Illustrations using microinterferogram, graphs, and tables are given. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Transport studies on thin films of Ag7I4VO4 solid electrolyte

Deposition of thin films of the solid electrolyte Ag₇I₄VO₄ by an electrodeposition technique is discussed. The X-ray diffraction technique has been used for the characterization of the films. Measurement of a.c. electrical conductivity in the temperature range 300–400 K showed that films deposited at 313 K and at a current density of 8 mAcm^–2 are of the best quality, having a typical conductivity of 1.5 x 10^-3-1cm^-1 at room temperature (305K) with an activation energy of 0.2eV. Dielectric studies carried out on the best quality films showed that Ag₇I₄VO₄ possesses a high value of dielectric constant ( 10⁵). The frequency dependence of the dielectric constant is explained as due to an interfacial polarization phenomenon. The behaviour of the dielectric ion suggests a Debye-type relaxation.     

Tailoring of optical band gap and electrical conductivity in a-axis oriented Ni doped Chromium Oxide thin films

Ni doped Cr₂O₃ (NCO) films have attracted much attention due to their applications in the field of photovoltaics. This study reports the tailoring of structural, electrical and optical properties as a function of Ni doping in Chromium oxide (Cr₂O₃). NCO thin films were grown by Pulsed laser deposition (PLD) using 2nd harmonic Nd:YAG Laser on n-Si (100) with in-situ annealing of 450?°C. Structural analyses based on X-ray diffractometry (XRD) and Raman Spectroscopy showed the inconsistent variation in crystallinity and shift in $A_{1g}$ band in turn revealing the successful incorporation of Ni into Chromium oxide host lattice. In addition, electrical measurements also showed an inconsistent variation in resistivity ranging from 10² to 10⁴$\Omega ?\mathit{cm}$. The properties showed widening of band gap energy (E_g) from 3.41 to 3.60?eV as a function of Ni doping concentration with significantly decreased reflectance in the range of 500–600?nm thereby increasing the absorption, a pre-requisite for solar absorbers.     

Flow-through and flow-by porous electrodes of nickel foam. I. Material characterization

This paper deals with the characterization of three nickel foams for use as materials for flow-through or flow-by porous electrodes. Optical and scanning electron microscope observations were used to examine the pore size distribution. The overall, apparent electrical resistivity of the reticulated skeleton was measured. The BET method and the liquid permeametry method were used to determine the specific surface area, the values of which are compared with those known for other materials.Nomenclature a _e specific surface area (per unit of total volume) (m^–1) - a _s specific surface area (per unit of solid volume) (m^–1) - (a _e)_BET specific surface area determined by the BET method (m^–1) - (a _e)_Ergun specific surface area determined by pressure drop measurements (m^–1) - mean pore diameter (m) - mean pore diameter determined by optical microscopy (m) - mean pore diameter using Ergun equation (m) - e thickness of the skeleton element of the foam (m) - G grade of the foam (number of pores per inch) - P/H pressure drop per unit height of the foam (Pa m^–1) - r electrical resistivity ( m) - R _h hydraulic pore radius (m) - T tortuosity - mean liquid velocity (m s^–1) Greek symbols mean porosity - circularity factor - dynamic viscosity (kg m^–1 s^–1) - liquid density (kg m^–3) - pore diameter size dispersion     

Irradiation effects on electrical properties of cellulose nitrate

Cellulose nitrate (CA-80-15) films were exposed to UV and neutron irradiations. An increase of the electrical conductivity was observed. The values of the activation energy diminish with irradiation from 0.42 to 0.15 eV for UV and to 0.31 eV for neutron irradiation. A sharp increase in the current was observed after exposing CA-80-15 samples to fission neutron fluences of 1*10⁷ n/cm². The electrical conduction in cellulose nitrate is governed by the Shottky mechanism. The value of the electron affinity of the polymer used is 4.46 eV. This value is increased after both types of irradiation. The dielectric permittivity (ε′) of the above samples together with the dielectric loss factor (ε″) were measured over a range of temperatures (293–403 K) at fixed frequencies (1*10³, 1*10⁴, and 1*10⁵Hz). Three neutron exposures (? = 1*10⁵, 1*10⁶, and 1*10⁷ n/cm²) were used. The obtained results made it possible to determine a complete set of conduction parameters including dielectric susceptibility χ, ac conductivity α_ac, and temperature coefficient of permittivity TC. © 1995 John Wiley & Sons, Inc.     

Chemical synthesis of polymers containing N-ethyl-3.7-phenothiazinediyl groups

Summary Poly(N-ethyl 3.7-phenothiazinediyl) (1) and poly (N-ethyl 3.7-phenothiazinediyl-co-acetylene) (2) were synthesized by homo- and copolycondensation of 3.7-dibromo N-ethylphenothiazine and 1.2-dibromoethene using a Grignard reaction and NiCl₂ or NiCl₂.2PPh₃ as catalyst. Polymers are soluble in common organic solvents and after doping with iodine have an electrical conductivity of 10^–7 –10^–6 cm^–1.     

Synthesis,electroconductivity and third-order nonlinear optical property of poly(2-isopropoxy-5-methoxy-1,4-phenylenevinylene)

Summary Asymmetrically disubstituted poly(2-isopropoxy-5-methoxy-1,4-phenylene-vinylene), PIMPV, was prepared in thin films via organic-soluble precursor polymer method. These polymer films could be easily stretched up to 7 times, and the drawn films of the PIMPV could be doped with FeCl₃ and I₂ to give conductivities of 26.9 and 11.3 Scm^-1, respectively. The third-order nonlinear optical susceptibility of the polymer was determined using third harmonic generation(THG) method at 1907 nm, fundamental wavelength. Measured ⁽³⁰⁾ (-3: , , ) value was 3.7x10^-12 esu.     

Electrical Properties and the Structure of Glasses in the xNa2O–(1 – x)2PbO · B2O3 System

The temperature–concentration dependences of the electrical conductivity and the activation energy for electrical conduction of glasses in the Na₂O–B₂O₃ and Na₂O–2PbO · B₂O₃ systems are studied. The investigation into the nature of the electrical conduction in these glasses reveals that the contribution from the electronic component (10^–3%) of the conductivity is within the sensitivity of the Liang–Wagner technique. A considerable alkali conductivity is observed upon introduction of more than 12 mol % Na₂O. The true transport number of sodium _Na is as large as unity at [Na₂O] 15 mol %. It is shown that the observed temperature–concentration dependences of the electrical and transport properties are governed by the ratio between the concentrations of polar and nonpolar structural–chemical units of the Na⁺[BO_4/2]^–, Na⁺[O^–BO_2/2] Na⁺[O^–BO_2/2], Pb²⁺ _1/2[BO_4/2]^–, Pb²⁺ _1/2[O^–BO_2/2], and [BO_3/2] types.     

EPR and optical studies on binary mixed alkali-alkaline earth oxide borate glasses doped with Cu<Superscript>2+</Superscript> ions

Mixed alkali alkaline earth oxide borate glasses of the composition (25 – x)Li₂O–xK₂O–12.5BaO–12.5MgO–49B₂O₃–1CuO (x = 0, 5, 10, 15 and 20 mol %) were prepared by the melt quenching technique. The X-ray diffractograms of all the glass samples were recorded at room temperature. Peak free X-ray spectra revealed the amorphous nature of all the prepared glasses. Modulated differential scanning calorimetry (MDSC) was used to determine the glass-transition temperature (T _g ). The probable mixed alkali effect was investigated using experimental techniques like density, molar volume, MDSC, electron paramagnetic resonance (EPR), and optical absorption studies. From the EPR spectra the spin-Hamiltonian parameters were evaluated. The spin-Hamiltonian parameter values indicated that the ground state of \(C{u^{2 + }}is{\kern 1pt} {d_{{x^2} - {y^2}}}\) orbital (²B_1g) and the site symmetry around Cu² is tetragonally distorted octahedral. The variation of g _|| and A _|| as a function of Li₂O content was found to be nonlinear. A broad optical absorption band was observed in all the glasses containing Cu² ions corresponding to ²B_1g → ²B_2g transition. From the optical absorption studies the values of the optical band gap (E _opt) for indirect, direct transitions and Urbarch energy (ΔE) have been evaluated. By co-relating the EPR and optical absorption data, bonding parameters α², β² and β ₁ ² were evaluated.     

A wall-jet electrode reactor and its application to the study of electrode reaction mechanisms Part I: Design and construction

A wall jet electrode reactor possessing a laminar flow regime, suitable for mechanistic studies, is reported. This reactor is different from those described in the literature in the size of its working electrode surface area. The reactor is evaluated by means of mass transport-limited current measurements using as a model reaction the reduction of ferricyanide ions at a platinum electrode surface from a 0.01 m K₃Fe(CN)₆-0.01 m K₄Fe(CN)₆ solution containing 1 m KCl as supporting electrolyte. The dependence of the mass transport-limited current on the crucial reactor parameters — the volume flow rate V _f (m³ s^–1), the nozzle diameter a (m) and the radius of the working electrode R (m) — is established and verified by theoretical predictions. The reactor is shown to have the desired wall jet hydrodynamics for: 1.6 × 10^–6 V _f 4.3 × 10^–6 m³ s^–1, 1.5 × 10^–3 a 3 × 10^–3 m and 1.5 × 10^–2 R 2 × 10^–2 m.List of symbols a nozzle diameter (m) - C _A concentration of A in the bulk (mol m^–3) - D _A diffusion coefficient of A (m² s^–1) - F Faraday's constant (C mol^–1) - dynamic viscosity (gm^–1 s^–1) - H distance between the working electrode and the tip of the nozzle (m) - I _lim mass-transport-limited current (A) - k _r constant linking the typical velocity of the wall-jet to the mean velocity in the nozzle - v kinematic viscosity (m² s^–1) - n number of electrons exchanged - density (g m^–3) - R radius of the working electrode (m) - t time (s) - V _f volume flow rate (m^–3 s^–1)     

Solution properties and unperturbed dimensions of poly (vinylpyrrolidone)

The dilute solution properties of nine poly(vinylpyrrolidone) fractions in methanol covering the molecular weight range 6.76 × 10⁴ to 1.02 × 10⁷ were studied. Constants a and K_m of the Mark-Houwink-Sakurada (M.H.S.) equation were found to be 0.60 and 2.64 × 10^?4 respectively using light scattering and intrinsic viscosity data and were compared with the literature values. The second virial coefficient, A₂ decreases gradually as the molecular weight increases while the root-mean-square radius of gyration, ² increases. The dependence of A₂ on molecular weight is in agreement with other flexible polymers dissolved in moderate to good solvents. The unperturbed chain dimension, (r/M) was calculated using the Stockmayer-Fixman (S—F) equation and a value of 4.9 × 10^?17 cm was obtained. The S—F plot slightly bends in the region of high molecular weight which is according to expectation.     

Deposition of carbon nitride films using an electron cyclotron wave resonance plasma source

Hydrogenated amorphous carbon nitride (a-C:N:H) has been synthesised using a high plasma density electron cyclotron wave resonance (ECWR) technique using N₂ and C₂H₂ as source gases, at different ratios and a fixed ion energy (80 eV). The composition, structure and bonding state of the films were investigated and related to their optical and electrical properties. The nitrogen content in the film rises rapidly until the N₂/C₂H₂ gas ratio reaches 2 and then increases more gradually, while the deposition rate decreases steeply, placing an upper limit for the nitrogen incorporation at 30 at%. For nitrogen contents above 20 at%, the band gap and sp³-bonded carbon fraction decrease from 1.7 to 1.1 eV and ∼65 to 40%, respectively. The transition is due to the formation of polymeric CN, CN and NH groups, not an increase in CH bonds. Films with higher nitrogen content are less dense than the original hydrogenated tetrahedral amorphous carbon (ta-C:H) film but, because they have a relatively high band gap (1.1 eV), high resistivity (10⁹ Ω cm) and moderate sp³-bonded carbon fraction (40%), they should be classed as polymeric in nature.     

The effect of temperature on limiting current density and mass transfer in electrodialysis

This study focuses on a high-temperature operation in electrodialysis of salt solutions and studies the effect of temperature on limiting current density and mass transfer. Experiments were conducted under various conditions of temperature (T), varying from 15 to 90°C; of dialysate concentration (C_d), varying from 5 × 10^?3 to 3 × 10^?2M ; and of dialysate velocity (u_d), varying from 0.206 to 2.44 cm s^?1. A least squares fitting of the experimental data on limiting current density (I_lim) yields an Arrhenius equation as follows: The molar flux N? (mol cm^?2 s^?1), initial concentration (C₀; M ) and temperature (T; °C) were found to have the following relationship: N?/C₀ is slightly increased with increasing temperature ranging from 25 to 70°C.     

Application of poly(phthalazinone ether sulfone ketone)s to gas membrane separation

A series of poly(phthalazinone ether sulfone ketone) (PPESK) copolymers containing different component ratios of bis(4‐fluorodiphenyl) ketone and bis(4‐chlorodiphenyl)sulfone with respect to a certain amount of 4‐(4‐hydroxyphenyl)‐2,3‐phthalazin‐1‐one were synthesized by polycondensation. Glass transition temperatures of these polymers were adjusted from 263°C to 305°C by changing the ratios of reactants. Gas permeability and selectivity of the dense membranes of the polymers for three kinds of gases (CO₂, O₂, and N₂) were determined at different temperatures. The result indicated that the membrane of PPESK (S/K = 1/1, mol ratio) had an excellent gas separation property. Permeability of the polymer membranes for CO₂, O₂, and N₂ was P = 4.121 barrier, P = 0.674 barrier, and P = 0.0891 barrier, respectively. Separation factors of α and α were 7.6 and 46, respectively. New material was made into a composite membrane with silicone rubber for blocking up leaks and defects on the surface of its nonsymmetrical membrane. As a result of the test, permeability of the composite membrane was J = 7.2 × 10⁻⁶ cm³ (STP) cm⁻² S⁻¹ cm⁻¹ Hg and J = 0.99 × 10⁻⁶ cm³ (STP) cm⁻² S⁻¹ cm⁻¹ Hg, whereas the α was still higher than 7. These showed that PPESKs had a bright prospect as the potential membrane material for high‐temperature gas separation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2385–2390, 1999     

Low bandgap EDOT-quinoxaline and EDOT-thiadiazol-quinoxaline conjugated polymers: Synthesis, redox, and photovoltaic device

Three new low bandgap conjugated copolymers with 3,4-ethylenedioxythiophene (EDOT) as donor and 2,3-bis(4-octyloxyphenyl)-quinoxaline (P1), 2,3-bis(4-octyloxyphenyl)-thiadiazol-quinoxaline (P2, P3) as acceptors were synthesized by Stille cross-coupling reaction, and their optical and electrochemical properties were studied. These polymers exhibited optical bandgap of 1.77, 1.29 and 1.13 eV, for P1, P2 and P3, respectively. Photovoltaic cells with device configuration of ITO/PEDOT: PSS/Copolymer: PCBM (1:4 w/w)/LiF/Al were fabricated. The measurements revealed an open-circuit voltage (V_oc) of 0.52 V, short-circuit current density (J_sc) of 3.24 mA/cm² and power conversion efficiency (PCE) of 0.60% for P1, and showed a V_oc of 0.33 V, J_sc of 2.11 mA/cm², PCE of 0.39% for P2.     

Temperature dependent dielectric properties of self‐standing and flexible poly(vinylidene fluoride) films infused with Er3+ doped GeO2 and SiO2 nanoparticles

The synthesis of Er³⁺@GeO₂ and Er³⁺@SiO₂ nanoparticle impregnated self‐standing poly(vinylidene fluoride) films by a facile solution casting technique has been reported. The prepared films were thoroughly characterized using X‐ray diffraction technique, field emission scanning electron microscopy, and transmission electron microscopy. The optical properties were evaluated using UV–Vis spectroscopy. Detailed study on the temperature dependent dielectric properties of the composite films with different Er³⁺ content were also investigated to establish the electrical properties of the same, which revealed the presence of different relaxation processes, namely, and ρ. Due to the smaller size, Er³⁺@SiO₂ was found to disperse better in the PVDF matrix than Er³⁺@GeO₂, which resulted in higher dielectric constant of the former at 300 K. At higher temperature (403 K), the behavior was reversed due to the formation of larger sized low mobility complexes. An investigation on ac conductivity proved the conduction mechanism for neat as well as composite PVDF films to follow the Correlated Barrier Hopping model. The loading of Er³⁺@GeO₂ and Er³⁺@SiO₂ nanoparticles in the PVDF matrix significantly enhances the dielectric properties without losing the flexibility of the composite films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44016.     

Zur Kinetik der photoinduziertenRadikalpolymerisation mit Elektronendonator/Elektronenakzeptor-Initiatorsystemen

Kinetics of Photoinduced Radical Polymerization with Electron Donor/Electron Acceptor Initiator Systems By means of benzyltriphenylphosphonium tetrafluoroborate (P^⊕) and anthracene (An) as photoinitiator system and methylmethacrylate (MMA) as monomer the influences of several reaction parameters on the polymerization quantum yield Φ_p, were studied. The following principal reactions proceed: electron transfer between excited An (¹An) and P^⊕ salt (k_q = 2,5 · 10⁹ M⁻¹ s⁻¹), quenching of ¹An by MMA (k = 1,3 · 10⁷ M⁻¹ s⁻¹), reaction between a ¹An…P^⊕ salt complex and MMA. The last reaction is assumed, since from the disappearance of An and the formation of An cation radical, respectively, rate constants k > 10⁸ M⁻¹ s⁻¹ have been calculated. Furthermore, it is assumed, that only the quenching of ¹An by MMA (Φ_p = 3,8) and the addition of free radicals, produced by the photoinduced electron transfer, lead to polymer formation. Kinetic equations were developed, which can explain the effect of P^⊕-salt concentration, light intensity and MMA concentration on Φ_p data. The quotient obtained for k_p/k is in the range of 0,053 to 0,087 M^−0,5 s^−0,5, depending on the used experimental parameters. Polymerization degrees P_n of 260–590 were found, which also depend on the experimental parameters.