Improvement in energy conversion of electrostrictive composite materials by new approach via piezoelectric effect: Modeling and experiments

This study proposes a new model that couples the piezoelectric and electrostrictive behavior to minimize the polarization power of composite polymer. The development of this model is capable to predict the energy harvesting abilities of an electrostrictive composite. To improve the dielectric permittivity of electrostrictive polymer, the particles of PZT have been incorporated in order to increase the conversion efficiency of the composite. Dielectric characterization tests showed an increase in dielectric permittivity by a factor of 4.5 compared to pure polymer. Experimental measurements of harvested power validate the analytical model and demonstrate a good correlation between the two data. An equivalent of an electrical scheme has been developed, which allows modeling the two behaviors. The harvested power density under low frequency at 2% of strain can reach 0.30 μW/cm³ for 33% of PZT without the polarization field, including the conversion efficiency becomes higher. The energy harvester property of this material composite has excellent potential for several self‐powered applications such as wireless sensor networks and the internet of things.     

Combination of electrostrictive polymers composites and electrets for energy harvesting capability

More recently, the development of electrostrictive polymers has generated novel opportunities for high‐strain actuators. At present, the investigation of using electrostrictive polymers for energy harvesting is beginning to show potential for this application. Basically, the relative energy gain depends on the current induced by the mechanical strain and frequency. The aim of the present experimental work is to study the composites on the basis of terpolymer P(VDF–TrFE–CFE) filled with low concentrations of copper (Cu) powders. The scanning electron microscopy was performed essentially to verify the dispersion of the fillers within the polymeric matrix. The obtained results showed a relatively homogeneous dispersion for the microsized fillers and the existence of agglomerates for their nanosized counterparts. On the other hand, our experimental data show that the harvested power as well as the current is significantly important for nano‐Cu fillers with respect to micro‐Cu fillers by a factor of 45.9% in the case of the hybridization of electrostrictive polymers and electrets. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and ionic conductivity of hyperbranched poly(glycidol)

A novel hyperbranched poly(glycidol) (HPG) was prepared and characterized. The synthesized HPG was used as a substrate of a polymer electrolyte. The ionic conductivity of a blend of HPG, polyurethane (PU), and salt was studied. The ionic conductivity of HPG/PU/LiClO₄ was about 6.6 × 10^?6 S · cm^?1 at 20 °C and 6.3 × 10^?4 S · cm^?1 at 60 °C. The results indicated that HPG showed higher solubility for salt than linear polyether when both had the same [O]/[Li⁺] molar ratio. The main reason was that more cavities and a lower degree of chain entanglement in HPG resulted in a lower glass‐transition temperature and were beneficial for decreasing the aggregation of salt or enhancing the ionic conductivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2225–2230, 2001     

A Ferroelectric Aminophosphonium Cyanoferrate with a Large Electrostrictive Coefficient as a Piezoelectric Nanogenerator

Hybrid materials possessing piezo- and ferroelectric properties emerge as excellent alternatives to conventional piezoceramics due to their merits of facile synthesis, lightweight nature, ease of fabrication and mechanical flexibility. Inspired by the structural stability of aminophosphonium compounds, here we report the first A₃BX₆ type cyanometallate [Ph₂(ⁱPrNH)₂P]₃[Fe(CN)₆] ( 1 ), which shows a ferroelectric saturation polarization (P_s) of 3.71 μC cm⁻². Compound 1 exhibits a high electrostrictive coefficient (Q₃₃) of 0.73 m⁴ C⁻², far exceeding those of piezoceramics (0.034–0.096 m⁴ C⁻²). Piezoresponse force microscopy (PFM) analysis demonstrates the polarization switching and domain structure of 1 further confirming its ferroelectric nature. Furthermore, thermoplastic polyurethane (TPU) polymer composite films of 1 were prepared and employed as piezoelectric nanogenerators. Notably, the 15 wt % 1 -TPU device gave a maximum output voltage of 13.57 V and a power density of 6.03 μW cm⁻².     

Piezoelectric Energy Harvesting from a Ferroelectric Hybrid Salt [Ph3MeP]4[Ni(NCS)6] Embedded in a Polymer Matrix

Organic–inorganic hybrid ferroelectrics are an exciting class of molecular materials with promising applications in the area of energy and electronics. The synthesis, ferroelectric and piezoelectric energy harvesting behavior of a 3d metal ion‐containing A₄BX₆ type organic–inorganic hybrid salt [Ph₃MeP]₄[Ni(NCS)₆] ( 1 ) is now presented. P‐E hysteresis loop studies on 1 show a remnant ferroelectric polarization value of 18.71 μC cm^?2, at room temperature. Composite thermoplastic polyurethane (TPU) devices with 5, 10, 15 and 20 wt % compositions of 1 were prepared and employed for piezoelectric energy harvesting studies. A maximum output voltage of 19.29 V and a calculated power density value of 2.51 mW cm^?3 were observed for the 15 wt % 1 ‐TPU device. The capacitor charging experiments on the 15 wt % 1 ‐TPU composite device shows an excellent energy storage performance with the highest stored energies and measured charges of 198.8 μJ and 600 μC, respectively.     

Polymer Electron Acceptors Based on Fluorinated Isoindigo Unit for Polymer Solar Cells

Most of efficient polymer electron acceptors for polymer solar cells (PSCs) are based on naphthalene diimide or perylene diimide as the electron deficient building block. In this paper, for the first time, we report polymer electron acceptors based on fluorinated isoindigo (F‐IID) as the electron deficient building block. We synthesized two polymer electron acceptors consisting of alternating F‐IID unit and thiophene/selenophen unit. They show low‐lying LUMO/HOMO energy levels of –3.69/–5.69 eV, high electron mobilities of 1.31×10^–5 cm²·V^–1·s^–1 and broad absorption spectra with the optical bandgap of 1.61 eV. PSC devices using the two F‐IID‐based polymers as polymer electron acceptors show encouraging power conversion efficiencies (PCEs) of up to 1.50% with an open‐circuit voltage (V_OC) of 0.97 V, a short‐circuit current density (J_SC) of 2.91 mA·cm^–2, and a fill factor (FF) of 53.2%. This work suggests a new kind of polymer electron acceptors based on F‐IID unit.     

Structure and electrical conductivity of ion-implanted rigid-rod and ladder polymers

Isotropic and oriented thin films of rigid-rod, rigid-rod pseudo-ladder, and ladder polymers were ion-bombarded with ⁸⁴Kr⁺ to a dose of 4 × 10¹⁶ ions/cm². The bombardment was conducted at two conditions: one at 190 keV energy with 0.12 μA/cm² current density and the other at 200 keV energy with 2.0 μA/cm² current density. With the low current density, the polymers developed a uniform ion-bombarded layer of about 0.35 μm at the surface. This layer showed an electrical conductivity on the order of 10^?3s/cm at ambient conditions, an enhancement of 6 to 9 orders of magnitude from the pristine polymers. The enhanced conductivity was found to decrease to 10^?6s/cm after the implanted krypton was removed by heating under reduced pressure. It suggests that the enhanced conductivity was due to a synergistic effect of structural change of the polymers and chemical doping by the im-planted ions. With the high current density, most polymer films, except that of rigid-rod pseudo-ladder poly(p-(2,5-dihydroxy) phenylene benzobisthiazole) (DPBT), developed an additional fibrous network structure over the uniform ion-bombarded layer. The comparable conductivity, 53 to 157 s/cm, measured for the various ion-bombarded films in-dicated that neither the molecular structure, rigid-rod or ladder, nor the molecular packing order, isotropic or oriented, constituted significant effect on the conductivity of ion-bombarded polymers. Since krypton could not be detected in the polymers ion-bombarded with high current density, the enhanced conductivity was attributed to the structural change of the polymers. The DPBT films ion-bombarded with high current density showed holes of micron size, probably due to the decomposition of hydroxy pendents from the rigid-rod backbone. © 1993 John Wiley & Sons, Inc.     

Syntheses,crystal structures,and magnetic properties of 1-D coordination polymers

Three coordination polymers of Robson-type macrocycles, {[Cu₄L¹(4,4′-bipy)₂]·4ClO₄·H₂O}_∞ (1), {[Cu₄L²(4,4′-bipy)₄]·2CH₃CN·4ClO₄·2H₂O}_∞ (2), and {[Zn₂L²(4,4′-bipy)₂]·(ClO₄)₂}_∞ (3) (where H₂L¹ and H₂L² are the [2?+?2] condensation products of 1,3-diaminopropane with 2,6-diformyl-4-methylphenol and 2,6-diformyl-4-fluorophenol, respectively), have been synthesized and characterized. Magnetic susceptibility was measured for 1 and 2 from 2 to 300?K. The optimized magnetic data were J?=?–368.5?cm^?1, J′?=?40.5?cm^?1 with R?=?1.69?×?10^?6 for 1 and J?=?–291.22?cm^?1, J′?=?83.74?cm^?1, ρ = 0.00168 with R?=?1.8?×?10^?11 for 2, respectively. The data reveal strong antiferromagnetic interactions between two Cu(II) ions in the macrocyclic unit and ferromagnetic interaction between the Cu(II) ions in two adjacent macrocyclic units for 1 and 2.     

Ozone reduction at Nafion modified Au electrode and the measurement of ozone concentration in highly resistive solutions

The mass transport and charge transfer kinetics of ozone reduction at Nafion coated Au electrodes were studied in 0.5 mol/L H2SO4 and highly resistive solutions such as distilled water and tap water. The diffusion coefficient and partition coefficient of ozone in Nafion coating are 1.78×10-6 cm2·s-1 and 2.75 at 25℃ (based on dry state thickness), respectively. The heterogeneous rate constants and Tafel slopes for ozone reduction at bare Au are 4.1×10-6 cm·s-1, 1.0×10-6 cm·s-1 and 181 mV, 207 mV in 0.5 mol/L H2SO4 and distilled water respectively and the corresponding values for Nafion coated Au are 5.5×10-6 cm·s-1, 1.1×10-6 cm·s-1 and 182 mV, 168 mV respectively. The Au microelectrode with 3 μm Nafion coating shows good linearity over the range 0-10 mmol/L ozone in distilled water with sensitivity 61 μA·ppm-1 ·cm-2, detection limit 10 ppb and 95% response time below 5 s at 25℃. The temperature coefficient in range of 11-30℃ is 1.3%.     

Efficient Piezoelectric Energy Harvesting from a Discrete Hybrid Bismuth Bromide Ferroelectric Templated by Phosphonium Cation

Bismuth containing hybrid molecular ferroelectrics are receiving tremendous attention in recent years owing to their stable and non-toxic composition. However, these perovskite-like structures are primarily limited to ammonium cations. Herein, we report a new phosphonium based discrete perovskite-like hybrid ferroelectric with a formula [Me(Ph)₃P]₃[Bi₂Br₉] ( MTPBB ) and its mechanical energy harvesting capability. The Polarization-Electric field (P-E) measurements resulted in a well-defined ferroelectric hysteresis loop with a remnant polarization value of 2.1 μC cm⁻². Piezoresponse force microscopy experiments enabled visualization of the ferroelectric domain structure and evaluation of the piezoelectric strain coefficient (d₃₃) for an MTPBB single crystal and thin film sample. Furthermore, flexible devices incorporating MTPBB in polydimethylsiloxane (PDMS) matrix at various concentrations were fabricated and explored for their mechanical energy harvesting properties. The champion device with 20 wt % of MTPBB in PDMS rendered a maximum peak-to-peak open-circuit voltage of 22.9 V and a maximum power density of 7 μW cm⁻² at an optimal load of 4 MΩ. Moreover, the potential of MTPBB -based devices in low power electronics was demonstrated by storing the harvested energy in various electrolytic capacitors.     

Polyacrylonitrile–lithium bis(oxalato) borate polymer electrolyte for electrical double layer capacitors

Lithium ion conducting polymer electrolytes based on polyacrylonitrile (PAN) and lithium bis(oxalato)borate (LiBOB) have been prepared and characterized. The polymer electrolytes having PAN:LiBOB weight ratios of 90:10, 80:20, 70:30, 60:40 and 50:50 were prepared using dimethylformamide as solvent. The electrolyte having the composition 50 wt.% PAN–50 wt.% LiBOB shows the highest room temperature conductivity of 2.55 × 10^?5 S cm^?1. This sample demonstrated a lithium ion transference number of 0.25 and a breakdown voltage of 1.6 V. The highest conducting electrolyte was then sandwiched between two symmetrical carbon electrodes to fabricate an electrical double layer capacitor (EDLC). The EDLCs were characterized using impedance measurement, cyclic voltammetry (CV) and galvanostatic charge–discharge tests. The capacitance obtained from impedance measurement is about 35 F g^?1 at frequency 10 mHz. From CV, the capacitance is calculated to be 24 F g^?1 at 10 mV s^?1 scan rate. The discharge capacitance of the EDLCs is determined in the range from 22 to 10 F g^?1 at corresponding discharge currents from 0.2 to 1.5 mA, respectively. This also corresponds to a specific energy from 3.01 to 1.47 W h kg^?1 and a specific power from 380 to 474 W kg^?1, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Oxyalkylene polymers with alkylsulfonylmethyl side chains: Gas barrier properties

Gas barrier properties of alkylsulfonylmethyl-substituted poly(oxyalkylene)s are discussed. Oxygen permeability coefficients of three methylsulfonylmethyl-substituted poly(oxyalkylene)s, poly[oxy(methylsulfonylmethyl)ethylene] (MSE), poly[oxy(methylsulfonylmethyl)ethylene-co-oxyethylene] (MSEE), and poly[oxy-2,2-bis (methylsulfonylmethyl)trimethylene oxide] (MST) were measured. MSEE, which has the most flexible backbone of the three polymers, had an oxygen permeability coefficient at 30°C of 0.0036 × 10⁻¹³ cm³(STP)·cm/cm²·s·Pa higher than that of MSE, 0.0014 × 10⁻¹³ cm³(STP)·cm/cm²·s·Pa, because the former polymer's T_g was near room temperature. MST with two polar groups per repeat unit and the highest T_g showed the highest oxygen permeability, 0.013 × 10⁻¹³ cm³(STP) · cm/cm²·s·Pa, among the three polymers, probably because steric hindrance between the side chains made the chain packing inefficient. As the side chain length of poly[oxy(alkylsulfonylmethyl)ethylene] increased, T_g and density decreased and the oxygen permeability coefficients increased. The oxygen permeability coefficient of MSE at high humidity (84% relative humidity) was seven times higher than when it was dry because absorbed water lowered its T_g. At 100% relative humidity MSE equilibrated to a T_g of 15°C after 2 weeks. A 50/50 blend of MSE/MST had oxygen barrier properties better than the individual polymers (O₂ permeability coefficient is 0.0007 × 10⁻¹³ cm³(STP)·cm/cm² ·s·Pa), lower than most commercial high barrier polymers. At 100% relative humidity, it equilibrated to a T_g of 42°C, well above room temperature. These are polymer systems with high gas barrier properties under both dry and wet conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 75–83, 1998     

Structural diversity for three Zn(II) coordination polymers from 4-nitrobenzene-1,2-dicarboxylate and bispyridyl ligand

Three Zn(II) complexes, [Zn₂(bpp)₂(FNA)₂]·H₂O (1), [Zn(bpp)(FNA)]·H₂O (2), and Zn₂(bpp)₂(FNA)₂ (3) (bpp = 1,3-bi(4-pyridyl)propane, H₂FNA = 4-nitrobenzene-1,2-dicarboxylic acid), were synthesized and characterized by single-crystal and powder X-ray diffraction methods, IR spectroscopy, TG analyses, elemental analyses, and fluorescent analysis. In 1, the Zn(II) ions are linked by FNA anions and bpp into 2-D layers. The Zn(II) ions in 2 are bridged by FNA anions into chiral chains, which are interlinked by bpp into 3-D metal–organic framework with (6⁵·8) CdS topology. Complex 3 features 1-D zigzag chains, which are interconnected by bpp ligands to give a 3-D framework with (6·7⁴·8)(6⁴·7·8) topology. Complexes 2 and 3 exhibit significant ferroelectric behavior (for 2 remnant polarization Pr = 0.050 μC cm^?2, coercive field Ec = 1.13 kV cm^?1, saturation of the spontaneous polarization Ps = 0.239 μC cm^?2; for 3 Pr = 0.192 μC cm^?2, Ec = 4.64 kV cm^?1, Ps = 0.298 μC cm^?2).     

Ionic conductivity of multiarm star polymer/LiClO4 electrolytes

A series of polymer electrolytes based on multiarm polymers and lithium salt complexes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and impedance measurement. The relationships of conductivity with salt concentration, temperature, and arm numbers are discussed. It is suggested that the star polymer has a higher solvency and ion transfer ability on lithium salts than on linear polymers. The conductivity maximum appeared at a higher salt concentration ([EO]/[Li] = 4). Impedance measurement suggested that the optimum conductivity was 2 × 10^?4 s · cm^?1. The conductivity increased with temperature and the dependence of ionic conductivity on temperature fits the Arrhenius equation. Among the studied systems, the star polymer with a five arm number performs better than other structures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4195–4198, 2004     

Selenium‐Substituted Diketopyrrolopyrrole Polymer for High‐Performance p‐Type Organic Thermoelectric Materials

Development of high‐performance organic thermoelectric (TE) materials is of vital importance for flexible power generation and solid‐cooling applications. Demonstrated here is the significant enhancement in TE performance of selenium‐substituted diketopyrrolopyrrole (DPP) derivatives. Along with strong intermolecular interactions and high Hall mobilities of 1.0–2.3 cm² V^?1 s^?1 in doping‐states for polymers, PDPPSe‐12 exhibits a maximum power factor and ZT of up to 364 μW m^?1 K^?2 and 0.25, respectively. The performance is more than twice that of the sulfur‐based DPP derivative and represents the highest value for p‐type organic thermoelectric materials based on high‐mobility polymers. These results reveal that selenium substitution can serve as a powerful strategy towards rationally designed thermoelectric polymers with state‐of‐the‐art performances.     

Microdetermination of acetone in aqueous solution

Diazotized anthranilic acid has been found to be a possible reagent for the spectrophotometric microdetermination of acetone in aqueous solution. The determination range is 10–130 μg/ml. The coefficient of variation does not usually exceed 12% for 60–130 μg of acetone but increases to 2.8% at the 10-μg level. The average relative error for five determinations ranges from ?1.5 to 2%. The molar absorptivity is 9.28 × 10³ liter · mol^?1 · cm^?1 in the presence of starch as a surfactant. Possible reaction path mechanism has been suggested for the colored body formation.     

The synthesis of poly(phenylacetylene)s with bulky chiral silyl groups and the thermal stability of their helical conformation

The polymerization of (−)‐p‐[(tert‐butylmethylphenyl)silyl]phenylacetylene (t‐BuMePhSi*PA) and (+)‐p‐[{methyl(α‐naphthyl)phenyl}silyl]phenylacetylene (MeNpPhSi*PA) with the [(nbd)RhCl]₂ Et₃N catalyst yielded polymers with very high molecular weights over 2 × 10⁶ in high yields. The optical rotations of the formed poly(t‐BuMePhSi*PA) and poly(MeNpPhSi*PA) were as high as −356 and −150° (c = 0.11 g/dL in CHCl₃), respectively. The circular dichroism (CD) spectrum of poly(t‐BuMePhSi*PA) in CHCl₃ exhibited very large molar ellipticities ([θ]) in the UV region: [θ]_max = 9.2 × 10⁴ ° · cm² · dmol⁻¹ at 330 nm and −8.0 × 10⁴ ° · cm² · dmol⁻¹ at 370 nm. The [θ]_max values of poly(MeNpPhSi*PA) were also fairly large: [θ]_max = 7.1 × 10⁴ ° · cm² · dmol⁻¹ at 330 nm and −5.3 × 10⁴ ° · cm² · dmol⁻¹ at 370 nm. The optical rotations of poly(t‐BuMePhSi*PA) and poly(MeNpPhSi*PA), measured in tetrahydrofuran, chloroform, and toluene solutions, were hardly dependent on temperature in the range 22–65 °C. The CD effects of these polymers hardly changed in the temperature range 28–80 °C, either. These results indicate that the helical structures of these polymers are thermally appreciably stable. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 71–77, 2001     

A Flexible Energy Harvester from an Organic Ferroelectric Ammonium Salt

Organic ferroelectrics due to their low cost, easy preparation, light weight, high flexibility and phase stability are gaining tremendous attention in the field of portable electronics. In this work, we report the synthesis, structure and ferroelectric behavior of a two-component ammonium salt 2 , containing a bulky [Bn(4-BrBn)NMe₂]⁺ (Bn=benzyl and 4-BrBn=4-bromobenzyl) cation and tetrahedral (BF₄)⁻ anion. The structural analysis revealed the presence of rich non-classical C−H⋅⋅⋅F and C−H⋅⋅⋅Br interactions in this molecule that were quantified by Hirshfeld surface analysis. The polarization (P) vs. electric field (E) hysteresis loop measurements on 2 gave a remnant polarization (P_r) of 14.4 μC cm⁻² at room temperature. Flexible polymer composites with various (5, 10, 15 and 20) weight percentages (wt%) of 2 in thermoplastic polyurethane (TPU) were prepared and tested for mechanical energy harvesting applications. A notable peak-to-peak output voltage of 20 V, maximum current density of 1.1 μA cm⁻² and power density of 21.1 μW cm⁻² were recorded for the 15 wt% 2 -TPU composite device. Furthermore, the voltage output generated from this device was utilized to rapidly charge a 100 μF capacitor, with stored energies and measured charges of 156 μJ and 121.6 μC, respectively.     

Synthesis and characterization of 1,3,4-thiadiazole-containing polyazomethines and copolyazomethines

Novel 1,3,4-thiadiazole-containing polyazomethines and copolyazomethines were synthesized by the solution polycondensation, in m-cresol at 25°C, of aromatic dialdehydes, isophthalaldehyde and terephthalaldehyde, with 2,5-bis (m-aminophenyl)-1,3,4-thiadiazole (BMAT) and with BMAT and aromatic diamines, bis (4-aminophenyl) ether and 1,5-diaminonaphthalene, respectively. These polymers were tan yellow to yellow in color and had reduced viscosities up to 0.32 dL/g in concentrated sulfuric acid and electric conductivity as high as 10^?9?10^?11 S cm^?1 at 25°C. All the polymers were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid and formic acid. However, they were readily hydrolyzed in concentrated sulfuric acid. X-ray diffraction diagrams showed that the crystallinity of polyazomethines were low, but copolyazomethines were highly crystalline. These azomethine polymers are highly thermally and thermooxidativelly stable and exhibited no appreciable decomposition up to 400°C in both air and nitrogen atmospheres. Doping with iodine dramatically raised the conductivity and produced the dark brown- to completely black-colored semiconductive polymers with a maximum conductivity of the order of 10^?5 S cm^?1. Electronic spectra of the undoped polymers indicated a large bathochromic shift of the π?π^* absorption band (310 nm) due to C?N bonds of BMAT. This result suggests that π-electrons of the polymers are extensively delocalized along the main chain.     

Silafluorene‐based polymers for electrochromic and polymer solar cell applications

In this study, four novel silafluorene (SiF) and benzotriazole (Btz) bearing conjugated polymers are synthesized. In the context of electrochemical and optical studies, these polymers are promising materials both for electrochromic device (ECD) and polymer solar cell (PSC) applications. All of the polymers are ambipolar (both p‐ and n‐dopable) and multichromic. Electrochemistry experiments indicate that incorporation of selenophene instead of thiophene unit increases the HOMO energy level of the polymers. Power conversion efficiency of the PSCs reached 1.75% for PTBTSiF, 1.55% for PSBSSiF, 2.57% for PBTBTSiF, and 1.82% for PBSBSSiF. The hole mobilities of the polymers are estimated through space charge limited current (SCLC) model. PBTBTSiF has the highest hole mobility as 2.44 × 10^?3 cm² V s^?1. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1541–1547