Optical and dielectric properties of PVP based composite polymer electrolyte films

Solid polymer electrolyte films were prepared by adding Al₂O₃ particles to poly(vinylpyrrolidone)-MgCl₂ ? 6H₂O salt using solution cast technique. Various analytical techniques have been applied to characterize the prepared polymer films such as XRD, SEM, UV–Vis spectroscopy and AC conductivity. The structural analysis of pure poly(vinylpyrrolidone) complexed with MgCl₂ ? 6H₂O salt showed orthorhombic lattice structure indicating its semi-crystalline nature. SEM analysis reveals the heterogeneous phase of nanocomposite polymer electrolyte systems. The conductivity of Al2O3 doped poly(vinylpyrrolidone) based solid polymer electrolyte was found to be 1.22 × 10^–6 S/cm at room temperature for 85: 15 weight composition. Electrochemical cell has been fabricated with the configuration Mg⁺/(PVP + MgCl₂ ? 6H₂O + Al₂O₃)/(I₂ + C + electrolyte) and its discharge characteristics were studied for a constant load of 100 kΩ. Various cell parameters such as open-circuit voltage, short circuit current, energy density and power density were calculated for the prepared samples.     

Enhanced zinc ion transport in gel polymer electrolyte: effect of nano-sized ZnO dispersion

The effect of the dispersion of zinc oxide (ZnO) nanoparticles in the zinc ion conducting gel polymer electrolyte is studied. Changes in the morphology/structure of the gel polymer electrolyte with the introduction of ZnO particles are distinctly observed using X-ray diffraction and scanning electron microscopy. The nanocomposites offer ionic conductivity values of >10^?3 S cm^?1 with good thermal and electrochemical stabilities. The variation of ionic conductivity with temperature follows the Vogel–Tamman–Fulcher behavior. AC impedance spectroscopy, cyclic voltammetry, and transport number measurements have confirmed Zn²⁺ ion conduction in the gel nanocomposites. An electrochemical stability window from ?2.25 to 2.25 V was obtained from voltammetric studies of nanocomposite films. The cationic (i.e., Zn²⁺ ion) transport number (t ₊) has been found to be significantly enhanced up to a maximum of 0.55 for the dispersion of 10 wt.% ZnO nanoparticles, indicating substantial enhancement in Zn²⁺ ion conductivity. The gel polymer electrolyte nanocomposite films with enhanced Zn²⁺ ion conductivity are useful as separators and electrolytes in Zn rechargeable batteries and other electrochemical applications.     

Mechanical and Electrochemical Properties of New Nanocomposite Polymer Electrolytes Based on Poly(vinylidene fluoride-co-hexafluoropropylene) and SiO<Subscript>2</Subscript> Addition

Nanocomposite polymer electrolytes based on the system poly(vinylidene fluoride-co-hexafluoropropylene)–liquid electrolyte 1 mol/L LiBF₄ in gamma-butyrolactone which is modified by introducing up to 10 wt % of SiO₂ nanopowder (an average particle size of 7 nm) are synthesized and characterized. The introduction of SiO₂ nanoparticles worsens the elasticity of films but increases their fracture stress to 24 MPa. The conductivity of the nanocomposite electrolytes containing SiO₂ nanoparticles is higher than that without SiO₂ and attains 3.7 mS/cm at 20°C for the electrolyte containing 1.25 wt % SiO₂. Upon the introduction of SiO₂ nanoparticles, the electrochemical stability of electrolytes grows by 0.50–0.85 V and attains 6.7 V relative to Li/Li⁺.     

Direct borohydride fuel cell performance using hydroxide-conducting polymeric nanocomposite electrolytes

Solid electrolyte membranes based on alkali-doped polyvinyl alcohol (PVA) and PVA/carbon nanotubes (PVA/CNTs) are used in direct borohydride fuel cells (DBFCs). As 0.05 wt % of CNT is incorporated into the PVA matrix, the polymer crystallinity is decreased from 42.4% to 38.0% and the fractional free volume increases from 2.48% to 3.53%. The KOH-doped PVA/CNT exhibits the highest ionic conductivity of 0.0805 S cm⁻¹, because of the increased polymer free volume (which promotes vehicular OH⁻ transport) and the presence of CNT (which serves as the conducting microchannels). Sodium borohydride (NaBH₄) in NaOH solution and potassium borohydride (KBH₄) in KOH mixture are fed into the cells. The power density of the KBH₄-based DBFC is almost twice that of the NaBH₄-based DBFC (184 vs. 92 mW cm⁻²) due to less KBH₄ permeability through the films, higher conductivity of the KOH-doped PVA composites than those in the sodium counterpart, and probably higher electro-catalytic kinetics. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1779–1789, 2013     

Preparation and characterization of pva based solid polymer electrolytes for electrochemical cell applications

Solid polymer electrolyte films containing poly(vinyl alcohol) (PVA) and magnesium nitrate (Mg(NO3)2) were prepared by solution casting technique and characterized by using XRD, FTIR, DSC and AC impedance spectroscopic analysis. The amorphous nature of the polymer electrolyte films has been confirmed by XRD. The complex formation between PVA and Mg salt has been confirmed by FTIR. The glass transition temperature decreases with increasing the Mg salt concentration. The AC impedance studies are performed to evaluate the ionic conductivity of the polymer electrolyte films in the range of 303 383 K, and the temperature dependence seems to obey the Arrhenius behavior. Transport number measurements show that the charge transport is mainly due to ions. Electrochemical cell of configuration Mg/(PVA + Mg(NO3)2) (70:30)/(I2 + C + electrolyte) has been fabricated. The discharge characteristics of the cell were studied for a constant load of 100 kΩ.     

Metal nanocomposite films prepared in situ from PVA and silver nitrate. Study of the nanostructuration process and morphology as a function of the in situ routes

Cast‐hybrid films composed of polyvinyl alcohol (PVA) and silver nitrate were treated according to three different ways, thermal annealing, UV‐irradiation, and chemical reduction by a borohydride solution, to obtain PVA/silver nanocomposite films. The nanostructuration process was studied as a function of the treatment conditions, and discussed as a function of the mobility state of the polymer chains in the nanocomposite matrix during treatment. A homogeneous dispersion of crystalline silver nanoparticles was obtained by thermal annealing above T_g and below T_m and UV‐lamp irradiation below T_g. For these two treatments, the major processing parameters were the annealing temperature and time and the UV‐exposure time, respectively. For low‐conversion rate in Ag(0), the films evolved upon ageing at room temperature. Totally different morphology and Ag(0) conversion were achieved by chemical reduction in a borohydride solution. All the silver ions were reduced into Ag(0), and crystalline silver nanoparticles layers parallel to the film surface were observed after the treatment. This morphology was related to the high‐swollen state of the polymer matrix during treatment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2062–2071, 2008     

Properties of a nanocomposite polymer electrolyte from an amorphous comb-branch polymer and nanoparticles

Three fully amorphous comb-branch polymers based on poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether of different molecular weights as side chains were synthesized. SiO₂ nanoparticles of various contents and the salt LiCF₃SO₃ were added to these comb-branch polymers to obtain nanocomposite polymer electrolytes. The thermal and transport properties of the samples have been characterized. The maximum conductivity of 2.8×10^–4 S cm^–1 is obtained at 28 °C. In the system the longer side chain of the comb-branch polymer electrolyte increases in ionic conductivity after the addition of nanoparticles. To account for the role of the ceramic fillers in the nanocomposite polymer electrolyte, a model based on a fully amorphous comb-branch polymer matrix in enhancing transport properties of Li⁺ ions is proposed.     

An electrochemical investigation on (MoO<Subscript>3</Subscript>+PVP+PVA) nanobelts for lithium batteries

Molybdenum trioxide (MoO₃) xerogel films modified with poly(vinyl alcohol)+poly(vinyl pyrrolidone) (PVP+PVA) polyblends were obtained by ion-exchange method with sol-gel technique. Investigations were conducted using X-ray “diffractometry”, Fourier transform infrared spectroscopy, and cyclic voltammetry. The results show that the H atoms in polyblend are H-bonded with the O atoms in the Mo=O bonds of MoO₃ xerogel, which effectively shield the electrostatic interaction between MoO₃ interlayer and Li⁺ ions when MoO₃ xerogel is modified by the intercalation of (PVP+PVA). The reversibility of the insertion/extraction of Li⁺ ions is greatly improved by the modification with polyblend of MoO₃ nanocomposite films. MoO₃ and (PVP+PVA) _x MoO₃ (x = 0, 0.5) nanobelts were obtained by a simple hydrothermal process from MoO₃ sol. The electrochemical cells with configuration Li/(LiPF₆+EC+DMC)/MoO₃ modified by (PVP+PVA) were fabricated and their discharge profiles studied.     

High Ionic Conductivity of Transparent Film of Hydroxyapatite and Poly(vinyl alcohol) Nanocomposite

Summary: Hydroxyapatite (HAp)-polyvinyl alcohol (PVA) nanocomposite film containing Li⁺ was designed as a solid polymer electrolyte. A composite was prepared by reacting Ca(OH)₂ with H₃PO₄ in the presence of PVA which is denatured in order to have the carboxyl group, and a LiN(CF₃SO₂)₂ was added. HAp particles were commonly formed in the shape of spindles (long axis ca. 80 nm and short axis ca. 25 nm). The obtained nanocomposite film, in which HAp particles were dispersed uniformly, is transparent, flexible and drawable. Its ionic conductivity is about 10⁻³ S/m at room temperature. This value is very large. This high ionic conductivity is considerable on the basis of the dynamic percolation theory.     

聚乙烯醇/聚乙烯吡咯烷酮碱性复合膜的制备及其性能

通过在不同浓度KOH溶液中进行掺杂,制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.详尽考察了膜的组成、微观结构、热稳定性、离子电导率和甲醇吸收率.结果表明,PVA与PVP两者具有较好的相容性,当m(PVA)∶m(PVP)=1∶0.5时,膜断面致密、均匀,未发生大尺度相分离.PVP的混入可以极大提高复合膜的电导率和热稳定性.当m(PVA)∶m(PVP)=1∶1时,复合膜的电导率可达2.01×10-3 S.cm-1.PVA/PVP/KOH膜的甲醇吸收率随温度的升高没有明显变化,100℃时其甲醇吸收率仅为同条件下Nafion 115膜的1/4.这表明该复合膜有望作为一种新型的碱性直接甲醇燃料电池用固体电解质膜且可提高膜的使用温度.     

Investigations on electrical properties of PVP:KIO4 polymer electrolyte films

Solid polymer electrolytes based on poly(vinyl pyrrolidone) (PVP) complexed with potassium periodide (KIO₄) salt at different weight percent ratios were prepared using solution-cast technique. X-ray diffraction (XRD) results revealed that the amorphous nature of PVP polymer matrix increased with the increase of KIO₄ salt concentration. The complexation of the salt with the polymer was confirmed by Fourier transform infrared (FTIR) spectroscopy studies. The ionic conductivity was found to increase with the increase of temperature as well as dopant concentration. The maximum ionic conductivity (1.421 × 10⁻⁴ S cm⁻¹) was obtained for 15 wt% KIO₄ doped polymer electrolyte at room temperature. The variation of ac conductivity with frequency obeyed Jonscher power law. The dynamical aspects of electrical transport process in the electrolyte were analyzed using complex electrical modulus. The peaks found in the electric modulus plots have been characterized in terms of the stretched exponential parameter. Optical absorption studies were performed in the wavelength range 200–600 nm and the absorption band energies (direct band gap and indirect band gap) values were evaluated. Using these polymer electrolyte films electrochemical cells were fabricated and their discharge characteristics were studied.     

Vibrational spectroscopy analysis of ion conduction mechanism in dispersed phase polymer nanocomposites

A novel combination of dispersed phase polymer nanocomposite electrolyte based on PEO₈‐LiClO₄+ x wt % nano‐CeO₂ has been investigated. A model for ion transport mechanism has been proposed to account for substantial enhancement of its electrical conductivity by ～ 2 orders of magnitude at low volume fraction of the filler reinforcement in the polymer nanocomposite films. The strength of the proposed model is based on unambiguous evidences from FTIR, TEM, and conductivity analysis. The FTIR results provide clear role of nanofiller concentration on ion–ion interaction quantified in terms of the fraction of free anion and ion‐pairs present in the nanocomposite films and its excellent correlation with conductivity versus filler concentration. The presence of asymmetry in the ν₄(ClO₄^?) band observed at 625 cm^?1 is attributed to its resolved degeneracy suggesting the presence of both uncoordinated and cation‐coordinated ClO₄^? anion in the matrix due to ion–ion and ion–filler interactions assisted by Lewis acid–base interaction. The enhancement in conductivity at low concentration is possibly due to direct interaction of nano‐CeO₂ with both polymer host and anions resulting in the release of ionic charges. Drastic conductivity reduction at higher concentration is related to charge immobilization because of ion/ion‐pair entrapment by local clusters of filler as evidenced in TEM. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 60–71, 2009     

Magnetic applications of polymer gels

In this paper we report results of both, material preparation and magnetic characterisation, on CoFe₂O₄ particles of nanometric size formed by in‐situ precipitation within polymer gels. The size of the particles was controlled within a very narrow volume distribution and its average value was shifted from 2 to 10 nm. The existence of nanoparticles showing, at room temperature, coercive field values between 500 and 900 Oe and saturation magnetisations of about 500 emu/cm³, suggest to use these systems to get magnetic recording media with ultra high density. Poly(vinyl alcohol) (PVA) and Polystyrene (PS) films were prepared from this nanocomposite material. After a magnetic field treatment nanoparticles within the PVA films are free to rotate in response to an applied magnetic field. This PVA based nanocomposite film portends a new class of magnetic material with very little or no electrical and magnetic loss.     

Preparation,surface morphology,and optical properties of indium(III) oxide nanoparticles by thermolysis of indium–poly(vinyl alcohol) coordination polymer

First report on the preparation of well-dispersed, indium(III) oxide (In₂O₃) nanoparticles with 22–35?nm size by polymer thermolysis is presented. Indium–poly(vinyl alcohol) (PVA) coordination polymer films were prepared by ‘solution casting technique’ from the homogeneous aqueous solution of coordination polymer prepared using PVA and indium(III) nitrate as starting materials; subsequently the films were calcined at 550?°C to yield In₂O₃ nanoparticles. Both indium–PVA coordination polymer that served as the precursor and the titled nanoparticles were characterized by Fourier transform-infrared spectroscopy, photoluminescence (PL), powder X-ray diffraction (XRD), transmission electron microscopy, and thermal analysis. Room temperature PL spectra of the prepared indium oxide nanoparticles showed intense blue emissions around 360, 410 and 430?nm, characteristic of indium oxide nanoparticles due to oxygen vacancies. The lower energy PL emission decreases with an increase of indium(III) content in the precursor. The size of the nanoparticles calculated from line broadening of XRD pattern (cubic; JCPDS: 06-0416) was found to be around 24?nm. The average particle size of the synthesized nanoparticles increased with metal ion content in the precursor coordination polymer.     

Nanocomposite blend gel polymer electrolyte for proton battery application

A proton-conducting nanocomposite gel polymer electrolyte (GPE) system, [35{(25 poly(methylmethacrylate) (PMMA) + 75 poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP))?+?xSiO₂}?+?65{1 M NH₄SCN in ethylene carbonate (EC) + propylene carbonate (PC)}], where x?=?0, 1, 2, 4, 6, 8, 10, and 12, has been reported. The free standing films of the gel electrolyte are obtained by solution cast technique. Films exhibit an amorphous and porous structure as observed from X-ray diffractometry (XRD) and scanning electron microscopy (SEM) studies. Fourier transform infrared spectrophotometry (FTIR) studies indicate ion–filler–polymer interactions in the nanocomposite blend GPE. The room temperature ionic conductivity of the gel electrolyte has been measured with different silica concentrations. The maximum ionic conductivity at room temperature has been observed as 4.3?×?10^?3?S?cm^?1 with 2 wt.% of SiO₂ dispersion. The temperature dependence of ionic conductivity shows a typical Vogel-Tamman-Fulcher (VTF) behavior. The electrochemical potential window of the nanocomposite GPE film has been observed between ?1.6 V and 1.6 V. The optimized composition of the gel electrolyte has been used to fabricate a proton battery with Zn/ZnSO₄·7H₂O anode and PbO₂/V₂O₅ cathode. The open circuit voltage (OCV) of the battery has been obtained as 1.55 V. The highest energy density of the cell has been obtained as 6.11 Wh?kg^?1 for low current drain. The battery shows rechargeability up to 3 cycles and thereafter, its discharge capacity fades away substantially.     

Synthesis,structural and optical properties of tin oxide nanoparticles and its CMC/PEG–PVA nanocomposite films

Polyethylene glycol–polyvinyl alcohol (PEG–PVA) blend is a multifunctional material and controlling its properties is important for various medical and industrial uses. In this paper, we report the influence of carboxymethyl cellulose (CMC) and doping with tin oxide (SnO₂) nanoparticles (NPs) on the structural and optical properties of PEG–PVA. The prepared samples were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and UV–Vis-NIR spectroscopies. SnO₂ NPs of rutile structure, average crystallite size of ～30.2 nm and optical band gap (E_g) of 3.68 eV were prepared by a simple sol–gel process. CMC addition enhances the crystallinity of PEG–PVA that then gradually reduced by increasing SnO₂ doping ratio. The optical transmittance of PEG–PVA increased from 77 to 90% after mixing with CMC and then decreased to 64% with increasing SnO₂ content to 1.5%. Also, the E_g of PEG–PVA increased from 5.20 to 5.28 eV and then decreased to 4.88 eV due to CMC addition and SnO₂ incorporation, respectively. The refractive index, the dispersion parameters and the optical conductivity of PEG–PVA, CMC/PEG–PVA and of its nanocomposite films are discussed. The correlation between the structural modifications and the resultant optical properties are reported.     

Effect of plasticizers (EC or PC) on the ionic conductivity and thermal properties of the (PEO)9LiTf: Al2O3 nanocomposite polymer electrolyte system

A new plasticized nanocomposite polymer electrolyte based on poly (ethylene oxide) (PEO)-LiTf dispersed with ceramic filler (Al₂O₃) and plasticized with propylene carbonate (PC), ethylene carbonate (EC), and a mixture of EC and PC (EC+PC) have been studied for their ionic conductivity and thermal properties. The incorporation of plasticizers alone will yield polymer electrolytes with enhanced conductivity but with poor mechanical properties. However, mechanical properties can be improved by incorporating ceramic fillers to the plasticized system. Nanocomposite solid polymer electrolyte films (200–600 μm) were prepared by common solvent-casting method. In present work, we have shown the ionic conductivity can be substantially enhanced by using the combined effect of the plasticizers as well as the inert filler. It was revealed that the incorporating 15 wt.% Al₂O₃ filler in to PEO: LiTf polymer electrolyte significantly enhanced the ionic conductivity [σ _RT (max)?=?7.8?×?10^?6 S cm^?1]. It was interesting to observe that the addition of PC, EC, and mixture of EC and PC to the PEO: LiTf: 15 wt.% Al₂O₃ CPE showed further conductivity enhancement. The conductivity enhancement with EC is higher than PC. However, mixture of plasticizer (EC+PC) showed maximum conductivity enhancement in the temperature range interest, giving the value [σ _RT (max)?=?1.2?×?10^?4 S cm^?1]. It is suggested that the addition of PC, EC, or a mixture of EC and PC leads to a lowering of glass transition temperature and increasing the amorphous phase of PEO and the fraction of PEO-Li⁺ complex, corresponding to conductivity enhancement. Al₂O₃ filler would contribute to conductivity enhancement by transient hydrogen bonding of migrating ionic species with O–OH groups at the filler grain surface. The differential scanning calorimetry thermograms points towards the decrease of T _g , crystallite melting temperature, and melting enthalpy of PEO: LiTf: Al₂O₃ CPE after introducing plasticizers. The reduction of crystallinity and the increase in the amorphous phase content of the electrolyte, caused by the filler, also contributes to the observed conductivity enhancement.     

Polyacrylamide/reduced graphene oxide-Ag nanocomposite as highly efficient antibacterial transparent film

In this study, preparation and characterization of polyacrylamide/reduced graphene oxide-Ag (PAM/rGO-Ag) nanocomposites as a new nanocomposite film were investigated. First, PAM/GO nanocomposite was synthesized by in situ polymerization strategy. Afterward, highly stable and uniformly distributed silver nanoparticles (Ag NPs) have been obtained with PAM/GO nanocomposite as nanoreactors via in situ reduction of silver nitrate (AgNO₃) using sodium borohydride (NaBH₄) as reducing agent. In addition, the prepared PAM/rGO-Ag nanocomposite was thermally annealed in order to achieve high-performance nanocomposite film with antimicrobial activities. The prepared nanocomposite was characterized by XRD, FT-IR, SEM, TEM and TGA. The obtained results demonstrate that the silver nanoparticles were well decorated and dispersed on the graphene oxide nanosheets. In fact, the GO nanosheets and polyacrylamide chains act as a support and stabilize the Ag nanoparticles. Moreover, antimicrobial activities of the films were also examined, and the films containing well-dispersed and stabilized Ag nanoparticles showed outstanding antibacterial activity.     

Specific features of the synthesis and the physicochemical properties of nanocomposite polymer electrolytes based on poly(ethylene glycol) diacrylate with the introduction of SiO<Subscript>2</Subscript>

The specific features of the synthesis and the physicochemical properties of new nanocomposite polymer electrolytes (NPE) based on poly(ethylene glycol) diacrylate, a liquid electrolyte, and silicon dioxide were studied. The kinetics of polymerization of the system in question were studied by isothermal calorimetry and the optimal conditions for the hardening of the NPE were selected. The dependence of the conductivity of the electrolyte samples on the amount of SiO₂ nanopowder introduced, the presence of preliminary ultrasonic treatment of the nanocomposite mixture before the synthesis, and the storage duration of the samples was studied using the electrochemical impedance method. The maximum conductivity (4.3?10^–3 S cm^–1 at 20 °C) was observed for samples without preliminary treatment with the introduction of 6 wt.% of SiO₂ and for the samples after ultrasonic treatment with 8 wt.% of SiO₂. The electrolyte films with the optimal SiO₂ content of 4 wt.% maintained their properties for 24 months.     

Pt and Pt–Ru nanoparticles decorated polypyrrole/multiwalled carbon nanotubes and their catalytic activity towards methanol oxidation

Conducting polymer composite films comprised of polypyrrole (PPy) and multiwalled carbon nanotubes (MWCNTs) [PPy–CNT] were synthesized by in situ polymerization of pyrrole on carbon nanotubes in 0.1 M HCl containing (NH₄)S₂O₈ as oxidizing agent over a temperature range of 0–5 °C. Pt nanoparticles are deposited on PPy–CNT composite films by chemical reduction of H₂PtCl₆ using HCHO as reducing agent at pH = 11 [Pt/PPy–CNT]. The presence of MWCNTs leads to higher activity, which might be due to the increase of electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces allowing higher dispersion and utilization of the deposited Pt nanoparticles. A comparative investigation was carried out using Pt–Ru nanoparticles decorated PPy–CNT composites. Cyclic voltammetry demonstrated that the synthesized Pt–Ru/PPy–CNT catalysts exhibited higher catalytic activity for methanol oxidation than Pt/PPy–CNT catalyst. Such kinds of Pt and Pt–Ru particles deposited on PPy–CNT composite polymer films exhibit excellent catalytic activity and stability towards methanol oxidation, which indicates that the composite films is more promising support material for fuel cell applications.