Conducting polymer coated textile based multilayered shields for suppression of microwave radiations in 8.2–12.4 GHz range

Polypyrrole (PPY) based conducting textiles were prepared by in situ polymerization of pyrrole over cotton fabric. The SEM micrographs show smooth and uniform coating of PPY over fabric with only few loose dendrites. The elemental analysis and XRD patterns revealed the presence of iron whereas magnetization measurement shows ferromagnetic signature with well defined hysteresis loop and saturation magnetization (Ms) of 0.3 emu/g. The good antistatic property and rapid static charge dissipability was reflected by decay profile with decay time of only 0.16 sec. In addition, the microwave absorption studies of multilayered shields; made up of these conducting fabrics; show absorption dominated total shielding effectiveness (SE_T) value of ?43.9 dB (i.e. >99.99% attenuation) which can be attributed to the better impedance matching, high microwave conductivity, shallow skin depth, and multiple scattering of incident electromagnetic radiation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

5‐Sulfoisophthalic acid monolithium salt doped polypyrrole/multiwalled carbon nanotubes composites for EMI shielding application in X‐band (8.2–12.4 GHz)

This article describes the synthesis and characterization of highly conductive polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT) composites prepared by in situ polymerization of pyrrole using 5‐sulfoisophthalic acid monolithium salt [lithio sulfoisophthalic acid (LiSiPA)] as dopant and ferric chloride as oxidant. Several samples were prepared by varying the amounts of MWCNTs ranging from 1 to 5 wt %. Scanning electron microscope and transmission electron microscope images clearly show a thick coating of PPy on surface of MWCNTs. The electrical conductivity of PPy increased with increasing amount of MWCNTs and maximum conductivity observed was 52 S/cm at a loading of 5 wt % of MWCNTs. Pure PPy prepared under similar conditions had a conductivity of 25 S/cm. Electromagnetic interference (EMI) shielding effectiveness (SE) also showed a similar trend and average EMI shielding of ?108 dB (3 mm) was observed for sample having 5 wt % MWCNT in the frequency range of 8.2–12.4 GHz (X‐band). The light weight and absorption dominated total SE of ?93 to ?108 dB of these composites indicate the usefulness of these materials for microwave shielding. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45370.     

Synthesis of nitropyridine‐based π‐conjugated polymers and their chemical properties

π‐Conjugated poly(3‐nitropyridine‐2,5‐diyl) ( PPy‐3‐NO₂ ), poly(3,3′‐dinitro‐2,2′‐bipyridine‐5,5′‐diyl) ( PBpy‐3,3′‐diNO₂ ), and a poly(arylene ethynylene) type polymer consisting of a 3,3′‐dinitro‐2,2′‐bipyridine unit ( PAE‐1 ) were synthesized by Cu‐promoted Ullmann coupling reaction and Pd‐catalyzed coupling reaction. PPy‐3‐NO₂ and PAE‐1 were soluble in organic solvents such as DMSO, DMF, and chloroform, and gel permeation chromatography analysis showed a number average molecular weight (M_n) of 9,300 and 12,300, respectively. PPy‐3‐NO₂ gave intrinsic viscosity, [η], of 0.53 dL g^?1 in DMF. PBpy‐3,3′‐diNO₂ had somewhat lower solubility. The polymers exhibited a UV–vis peak at about 430 nm. PPy‐NO₂ received electrochemical reduction at ?1.5 V versus Ag⁺/Ag in acetonitrile, and gave an electrochemical redox cycle in a range from 0 to ?1.1 V versus Ag⁺/Ag in an aqueous solution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1763–1767, 2006     

Synthesis and chemical properties of electrochromic π‐conjugated polyphenylenes with pendant viologen‐TCNQ salts

Polyphenylene (PP) with NH₂ side groups, namely, PFluNH ₂ , was synthesized by the Pd‐catalyzed reaction of 2,5‐dibromoaniline with 9,9‐dihexylfluorene‐2,7‐diboronic acid bis(1,3‐propanediol) ester. The reaction of PFluNH ₂ with 1‐hexyl‐1′‐(2,4‐dinitrophenyl)‐4,4′‐bipyridinium diiodide ( SaltBPy(I^?) ) eliminated 2,4‐dinitroaniline to yield PPs with viologen (1,1′‐disubstituted 4,4′‐bipyridinium dications), PFluBPy(I^?) . The reaction of PFluBPy(I^?) with Li⁺TCNQ ^? resulted in anion exchange between Cl ^? and TCNQ ^? , and yielded PFluBPy(TCNQ^?) . The reaction of PFluBPy(TCNQ^?) with the neutral TCNQ⁰ resulted in an interaction between TCNQ ^? and TCNQ⁰, and yielded PFluBPy(TCNQ^?‐TCNQ⁰) . Cyclic voltammetry measurements suggested that an electrochemical reduction of the viologen moiety and oxidation of the polymer backbone within PFluBPy(TCNQ^?) and PFluBPy(TCNQ^?‐TCNQ⁰) . Furthermore, this reaction was accompanied by electrochromism. The electric conductivities (σ) of the pellets molded from PFluBPy(TCNQ^?) to PFluBPy(TCNQ^?‐TCNQ⁰) were 2.7 × 10 ^{? 4} and 4.2 × 10 ^{? 4} Scm ^{? 1}, respectively; these σ values were higher than that observed for PFluNH ₂ (σ < 10 ^{? 8} Scm ^{? 1}) due to the self‐doping in the polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,chemical, and thermoelectric properties of n‐type π‐conjugated polymer composed of 1,2,4‐triazole and pyridine rings and its metal complexes

A soluble n‐type π‐conjugated polymer ( polymer 1 ) composed of a 1,2,4‐triazole ring substituted by a 4‐n‐octylphenyl subunit at the 4‐position of the 1,2,4‐triazole ring and pyridine‐2,5‐diyl rings was synthesized by Ni(cod)₂ (cod = 1,5‐cyclooctadiene) promoted dehalogenation polycondensation of 3,5‐bis(2‐bromopyridyl)‐4‐n‐octylphenyl‐1,2,4‐triazole ( monomer 1 ). A polymer complex ( polymer‐BiCl₃ ) was synthesized by the reaction of polymer 1 with BiCl₃. The UV–vis spectrum of polymer 1 exhibited an absorption maximum (λ_max value) at a longer wavelength than that exhibited by monomer 1 revealing that its π‐conjugation system was expanded along the polymer chain. Polymer 1 was electrochemically active in film, and the electrochemical reaction was accompanied with electrochromism. Thermoelectoric properties of polymer 1 and polymer‐BiCl₃ were investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39928.     

Effect of BaTiO3 on the microwave absorbing properties of Co‐doped Ni‐Zn ferrite nanocomposites

Coprecipitation and hydrothermal method were utilized for the synthesis of Co‐doped Ni‐Zn ferrite and barium titanate nanoparticles. The microwave absorption properties of Co‐doped Ni‐Zn ferrite/barium titanate nanocomposites with single layer structure were studied in the frequency range of 8.2–12.4 GHz.The spectroscopic characterizations of the nanocomposites were examined using X‐ ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering measurement. Thermogravimetric analysis indicated the high thermal stabilities of the composites. The composite materials showed brilliant microwave absorbing properties in a wide range of frequency in the X‐band region with the minimum return loss of ?42.53 dB at 11.81 GHz when sample thickness was 2 mm and the mechanisms of microwave absorption are happening mainly due to the dielectric loss. Compared with pure Co‐doped Ni‐Zn ferrite, Co‐doped Ni‐Zn ferrite/BaTiO₃ composites exhibited enhanced absorbing properties. The microwave absorbing properties can be modulated by controlling the BaTiO₃ content of the absorbers and also by changing the sample thicknesses. Therefore, these composites can be used as lightweight and highly effective microwave absorbers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39926.     

Preparation and characterization of an amphiphilic macrophotoinitiator based on 2‐hydroxyl‐2‐methyl‐1‐phenylpropanone

On the basis of 2‐hydroxyl‐2‐methyl‐1‐phenylpropanone (HMPP) and poly(ethylene glycol) (PEG), we prepared amphiphilic macrophotoinitiators (HMPP–PEG–HMPP) by first reacting HMPP with isophorone diisocyanate and subsequently reacting it with PEGs with different chain lengths. Fourier transform infrared spectroscopy, high‐performance liquid chromatography, and ¹H‐NMR were used to confirm the structure of the amphiphilic macrophotoinitiators. Ultraviolet (UV) absorption spectra showed that the amphiphilic macrophotoinitiators had maximum absorption wavelengths that were similar to those of the low‐molecular‐weight photoinitiator HMPP. The photolysis rate of the amphiphilic macrophotoinitiators was slightly lower than that of HMPP, but the migration rate of the amphiphilic macrophotoinitiators from a UV‐cured matrix was much lower compared to that of HMPP. Because of their amphiphilic nature, these macrophotoinitiators may play roles as both photoinitiators and emulsifiers, and they have been applied to the solution polymerization of water‐soluble monomer acrylamide in water and the emulsion polymerization of methyl methacrylate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43910.     

Review of electronic and optical properties of semiconducting π‐conjugated polymers: applications in optoelectronics

A general overview of the optoelectronic properties of π‐conjugated polymers is presented. Two types of polymer are discerned: interchangeable structures of the same energy (degenerate), such as polyacetylene; and non‐degenerate polymers, such as poly(para‐phenylene). The band structures of degenerate and non‐degenerate polymers are related to their conductivities in doped and non‐doped states. In both cases, disorder and impurities play an important role in conductivity. Polarons, bipolarons and excitons are detailed with respect to doping and charge transfers. Given the fibrillic nature of these materials, the variable range hopping (VRH) law for semiconducting polymers is modified to account for metallic behaviours. Optoelectronic properties—electroluminescence and photovoltaic activity—are explained in terms of HOMO and LUMO bands, polaron‐exciton and charge movement over one or more molecules. The properties of H‐ or J‐type aggregates and their effects on transitions are related to target applications. Device structures of polymer light‐emitting diodes are explicitly linked to optimising polaron recombinations and overall quantum efficiencies. The particularly promising use of π‐conjugated polymers in photovoltaic devices is discussed. Copyright © 2004 Society of Chemical Industry     

Improved dielectric properties in A′‐site nickel‐doped CaCu3Ti4O12 ceramics

The improved dielectric properties and voltage‐current nonlinearity of nickel‐doped CaCu₃Ti₄O₁₂ (CCNTO) ceramics prepared by solid‐state reaction were investigated. The approach of A′‐site Ni doping resulted in improved dielectric properties in the CaCu₃Ti₄O₁₂ (CCTO) system, with a dielectric constant ε′≈1.51×10⁵ and dielectric loss tanδ≈0.051 found for the sample with a Ni doping of 20% (CCNTO20) at room temperature and 1 kHz. The X‐ray photoelectron spectroscopy (XPS) analysis of the CCTO and the specimen with a Ni doping of 25% (CCNTO25) verified the co‐existence of Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺. A steady increase in ε′(f) and a slight increase in α observed upon initial Ni doping were ascribed to a more Cu‐rich phase in the intergranular phase caused by the Ni substitution in the grains. The low‐frequency relaxation leading to a distinct enhancement in ε′(f) beginning with CCNTO25 was confirmed to be a Maxwell‐Wagner‐type relaxation strongly affected by the Ni‐related phase with the formation of a core‐shell structure. The decrease of the dielectric loss was associated with the promoted densification of CCNTO and the increase of Cu vacancies, due to Ni doping on the Cu sites. In addition, the Ni dopant had a certain effect on tuning the current‐voltage characteristics of the CCTO ceramics. The present A′‐site Ni doping experiments demonstrate the extrinsic effect underlying the giant dielectric constant and provides a promising approach for developing practical applications.     

Effect of microstructure on the dielectric properties of poly(vinyl alcohol)–poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) composite films

Poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS) was blended with poly(vinyl alcohol) (PVA) to form 0, 10, 20, 30, 40, and 50 vol % PEDOT–PSS/PVA solutions, and their freestanding films were prepared with a simple and cost‐effective solution casting technique at 27 °C in the absence of additives. Field emission scanning electron microscopy images revealed changes in the cocontinuous network to a rodlike morphology in the composite films from 10 to 50 vol % PEDOT–PSS/PVA. The alternating‐current conductivity was found to obey Jonscher's power law. The obtained values of the dielectric constant at 27 °C were relatively high, and a maximum value of 6.7 × 10⁴ at 100 Hz for 40 vol % PEDOT–PSS'/PVA was observed. The dielectric loss attained a maximum value of about 10⁶ at 100 Hz for 40 vol % PEDOT–PSS/PVA. However, a decrease in the dielectric parameters was observed at 50 vol % PEDOT–PSS/PVA because of locally induced strain in the microstructure. The variations in polarization with respect to the applied electric field (P–E) were determined for 50, 100, and 500 Hz at 500 V for the freestanding composite films of lower concentrations up to 20 vol % PEDOT–PSS/PVA. In summary, the dielectric and P–E measurements confirmed that the electrical characteristics changed in accordance to the contribution from both resistive and capacitive sites in the PEDOT–PSS/PVA composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45079.     

Photo‐ and electroluminescent properties of a π‐conjugated copolymer containing 2,2′‐bipyridyl units

The synthesis, structural characteristics, and photo‐ and electroluminescent properties of a soluble light‐emitting copolymer built up of regularly alternating segments of 1,4‐dihexyloxybenzene and 2,2′‐bipyridyl (PBPyDHB) are described and discussed. Optical properties of the polymer were investigated in solution and solid‐state conditions, demonstrating that in film form the predominant emission centers are inter‐macromolecular aggregates, either in photo‐ or electroluminescence. Thermogravimetric analysis indicates that PBPyDHB has very high thermal stability, with a maximum decomposition rate around 400 °C and onset with 10% mass loss at 342 °C. The polymer is a blue emitter, and the good solubility, thermal behavior, and electroluminescence properties make it a promising material for electro‐optical applications. Copyright © 2006 Society of Chemical Industry     

Microwave dielectric and nonlinear optical studies on radio‐frequency sputtered Dy2O3‐doped KNN thin films

We report the effect of oxygen mixing percentage (OMP) on structural, microstructural, dielectric, linear, and nonlinear optical properties of Dy₂O₃‐doped (K_0.5Na_0.5)NbO₃ thin films. The (K_0.5Na_0.5)NbO₃ + 0.5 wt%Dy₂O₃ (KNN05D) ferroelectric thin films were deposited on to quartz and Pt/Ti/SiO₂/Si substrates by RF magnetron sputtering. An increase in the refractive index from 2.08 to 2.21 and a decrease in the optical bandgap from 4.30 to 4.28 eV indicate the improvement in crystallinity, which is also confirmed from Raman studies. A high relative permittivity (ε_r=281‐332) and low loss tangent (tanδ=1.2%‐1.9%) were obtained for the films deposited in 100% OMP, measured at microwave frequencies (5‐15 GHz). The leakage current of the films found to be as low as 9.90×10^?9 A/cm² at 150 kV/cm and Poole‐Frenkel emission is the dominant conduction mechanism in the films. The third order nonlinear optical properties of the KNN05D films were investigated using modified single beam z‐scan method. The third order nonlinear susceptibility (?χ⁽³⁾?) values of KNN05D films increased from 0.69×10^?3 esu to 1.40×10^?3 esu with an increase in OMP. The larger and positive nonlinear refractive index n₂=7.04×10^?6 cm²/W, and nonlinear absorption coefficient β=1.70 cm/W were obtained for the 100% OMP film, indicating that KNN05D films are good candidates for the applications in nonlinear photonics and high‐frequency devices.     

Acrylic pressure‐sensitive adhesives with nanodiamonds and acid–base dependence of the pressure‐sensitive adhesive properties

A high performance and functional properties in pressure‐sensitive adhesives (PSAs) are attractive in fundamental and industrial fields. To control the performance of PSAs, nanofillers have been loaded into them. In this study, we focused on composites of acrylic PSAs and nanodiamonds (NDs). The loaded NDs reinforced the mechanical properties and increased the performance of the PSAs. NDs in a PSA formed a network structure. In this study, we revealed that the acidic–basic state was a key factor in the control of the dispersion of the NDs. When a PSA emulsions and ND aqueous dispersion was mixed under basic conditions, the composites demonstrated higher PSA properties (tack, holding, and peeling strength). We investigated the effect of the ND loading on the PSA properties from the viewpoints of the nanostructure and acid–base interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46349.     

Semicontinuous emulsion copolymerization of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose (3‐MDG) and butyl acrylate (BA). Monomer feed addition

New polymer colloids based on the saccharide monomer, using of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (3‐MDG), were prepared by semicontinuous emulsion polymerization, a widely used industrial process. The copolymerization of 3‐MDG and butyl acrylate (BA), by the monomer‐addition technique, at 70°C, using sodium persulfate (Na₂S₂O₈) as an initiator, was investigated. The influence of some reaction parameters, such as the type and concentration of the surfactants as well as the monomer addition rate (R_m) on the polymerization rate (R_p), the colloidal properties, and the stability of the latexes, was studied. It was found that under starved‐feed conditions the polymerization rate and the particle size (D) increased with an increasing rate of monomer addition. The weight‐average molecular weight (M _w) also increased by enhancing R_m and a narrower molecular weight distribution was obtained. Furthermore, the type and the concentration of the surfactants strongly influenced the particle size and its distribution. The effect of the seed stage on the particle size and its distribution was also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2091–2102, 2003     

Thermal,electrical, and dielectric properties of reduced graphene oxide–polyaniline nanotubes hybrid nanocomposites synthesized by in situ reduction and varying graphene oxide concentration

In this study, reduced graphene oxide (RGO) has been introduced as conductive filler within polyaniline (PAni) nanotubes (PAniNTs) by in situ chemical reduction method to enhance the properties of PAniNTs. The effect of varied concentration of in situ reduced GO on the structural, thermal, electrical, and dielectric properties of RGO–PAniNTs nanocomposites have been investigated by high resolution transmission electron microscope, X‐ray diffraction, Fourier transform infrared, thermogravimetric analysis, I–V characteristics, and impedance analyzer. The enhanced thermal stability of the nanocomposites has been analyzed from the derivative thermogravimetric curves in terms of onset and rapid decomposition temperature. The transport mechanisms have been studied by fitting the nonlinear I–V characteristics to the Kaiser model. The dielectric relaxation phenomena have been investigated by permittivity and modulus formalisms. Characteristic relaxation frequency of RGO–PAniNTs nanocomposites shifts toward higher frequency with increasing RGO concentration indicating a distribution in conductivity relaxation. The distribution of relaxation time has been studied by fitting the imaginary modulus spectra of the nanocomposites to Bergman modified KWW function. The ac conductivity spectra are fitted to the Jonscher's power law equation and enhanced conductivity value of 1.26 × 10⁻³ S cm⁻¹ is obtained for 40 wt % of RGO compared to 1.22 × 10⁻⁴ S cm⁻¹ for PAniNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45883.     

Synthesis of poly(butyl acrylate)‐poly(methyl methacrylate) core–shell nanomaterials of anti‐crease‐whitening properties

Core–shell nanomaterials of poly(butyl acrylate)‐poly(methyl methacrylate) were synthesized using a differential microemulsion polymerization method for being used as polyacrylate‐based optical materials, which meet the requirement of anti‐crease‐whitening and proper mechanical strength. The effects of reaction temperature and surfactant amount on the particle sizes, as well as the effect of reaction temperature on the conversion and solid content were investigated to reveal the dependence of the application properties on the reaction conditions. The spherical morphology of core–shell nanoparticles was also studied via transmission electron microscopy. The resulting polymers with a core–shell monomer ratio of butyl acrylate/methyl methacrylate at 32/10 (vol/vol) demonstrated the optimal balanced properties in the anti‐crease‐whitening and mechanical property, confirmed by the visible light transmittance measurement and the dynamic analysis of the viscoelastic properties of the synthesized core–shell nanomaterials. The smaller the particle size, the better the transparency of the resulting polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39991.     

Remarkable piezoelectricity and stable high‐temperature dielectric properties of quenched BiFeO3–BaTiO3 ceramics

Effects of quenching process on dielectric, ferroelectric, and piezoelectric properties of 0.71BiFeO₃?0.29BaTiO₃ ceramics with Mn modification (BF–BT?xmol%Mn) were investigated. The dielectric, ferroelectric, and piezoelectric properties of BF–BT?xmol%Mn were improved by quenching, especially to the BF–BT?0.3 mol%Mn ceramics. The dielectric loss tanδ of quenched BF–BT?0.3 mol%Mn ceramics was only 0.28 at 500°C, which was half of the slow cooling one. Meanwhile, the remnant polarization P_r of quenched BF–BT?0.3 mol%Mn ceramics increased to 21 μC/cm². It was notable that the piezoelectric constant d₃₃ of quenched BF–BT?0.3 mol%Mn ceramics reached up to 191 pC/N, while the T_C was 530°C, showing excellent compatible properties. The BF–BT?xmol%Mn system ceramics showed to obey the Rayleigh law within suitable field regions. The Rayleigh law results indicated that the extrinsic contributions to the dielectric and piezoelectric responses of quenched BF–BT?xmol%Mn ceramics were larger than the unquenched ceramics. These results presented that the quenched BF–BT?xmol%Mn ceramics were promising candidates for high‐temperature piezoelectric devices.     

Synthesis and magnetic properties of novel fully conjugated polymeric complexes containing 1,10‐phenanthroline

A novel fully conjugated polymer containing 1,10‐phenanthroline (DAPcDOD) was first synthesized by the polycondensation of 2,7‐dimethyl‐2,4,6‐octatriene‐1,8‐dial with 5,6‐diamine‐1,10‐phenanthroline. Three polymeric complexes were first prepared by the reaction of DAPcDOD with NiSO₄, CoCl₂, and FeSO₄, respectively. The structures of the polymer and the complexes were characterized by IR, ¹H‐NMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0–50 kOe) at 5 K and as a function of temperature (5–300 K) at a magnetic field strength of 30 kOe. The results show that DAPcDOD–Ni²⁺ and DAPcDOD–Co²⁺ were soft ferromagnets, whereas DAPcDOD–Fe²⁺ exhibited the features of an antiferromagnet. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhanced magnetic and dielectric properties of Ti‐doped YFeO3 ceramics

Polycrystalline YFeO₃ (YFO) and YFe_1?(4/3)xTi_xO₃(YFTO) ceramics were prepared using the powder synthesized from the sol‐gel route. X‐ray diffraction analyses of the polycrystalline ceramics revealed the crystallization of the phase in orthorhombic crystal structure associated with the space group Pnma. The magnetization versus magnetic field hysteresis loops were obtained at room temperature for YFO and YFTO ceramics. The magnetic property changes from weak ferromagnetic in YFO to ferromagnetic in YFTO ceramics. The dielectric constant recorded at room temperature for YFTO ceramics was six times higher than that of YFO, whereas the dielectric loss gets reduced to 0.06 from 0.3 for YFO at 1 kHz. Impedance spectroscopy study carried out on YFO and YFTO ceramics confirmed the existence of non‐Debye‐type relaxation. Observed single semicircle in Z′ vs ?Z′′ plot established the incidence of intrinsic (bulk) effect and ruled out any grain boundary or electrode effects. The mechanism for the dielectric relaxation and electrical conduction process observed in YFO and YFTO ceramics was discussed by invoking electric modulus formalisms. Activation energy obtained by ac conductivity study suggested that the conduction process in YFO was linked up with the existence of the polaron and oxygen vacancies, whereas only oxygen vacancies contribute to the conduction process in YFTO ceramics.     

Synthesis of two D‐π‐A polymers π‐bridged by different blocks and investigation of their photovoltaic property

The synthesis, characterization, photophysical and photovoltaic properties of two 5,6‐bis(octyloxy)benzo[c][1,2,5]thiadiazole‐containing wide‐band‐gap donor and acceptor D‐π‐A alternating conjugated polymers (HSD‐a and HSD‐b) have been reported. These two polymers absorb in the range of 300–700 nm with a band gap of about 1.88 and 1.97 eV. The HOMO energy levels were ?5.44 eV for HSD‐a and ?5.63 eV for HSD‐b. Polymer solar cells with HSD‐b :PC₇₁BM as the active layer demonstrated a power conversion efficiency (PCE) of 2.59% with a high V_oc of 0.93 V, a J_sc of 7.3 mA/cm², and a comparable fill factor (FF) of 0.38 under simulated solar illumination of AM 1.5G (100 mW/cm²) without annealing. In addition, HSD‐a :PC₇₁BM blend‐based solar cells exhibit a PCE of 2.15% with a comparable V_oc of 0.64 V, J_sc of 8.75 mA/cm^?2, and FF of 0.40. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41587.