Infrared and conductivity studies on blends of PMMA/PEO based polymer electrolytes

Poly(methylmetacrylate)/poly(ethylene oxide) (PMMA/PEO) based polymer electrolytes were synthesized using the solution cast technique. Four systems of PMMA/PEO blends based polymer electrolytes films were investigated:

1. PMMA/PEO system,
2. PMMA/PEO + ethylene carbonate (EC) system,
3. PMMA/PEO + lithium hexafluorophosphate (LiPF₆) system and
4. PMMA/PEO + EC + LiPF₆ system.

The polymer electrolytes films were characterized by Impedance Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The FTIR spectra show the complexation occurring between the polymers, plasticizer and lithium salt. The FTIR results give further insight in the conductivity enhancement of PMMA/PEO blends based polymer electrolytes.     

Effect of montmorillonite filler on structural and electrical properties of polymer nanocomposite electrolytes

Polymer–clay nanocomposites consisting of polymer (polyethylene oxide) and NaI as salt with different concentration of organically modified Na⁺-montmorillonite (DMMT) have been fabricated and characterized. X-ray diffraction analysis shows that the polymer–salt complexes have been intercalated into the nanometric silicate layers of DMMT. Fourier transform infrared analysis shows that the polymer structure in the clay interlayer is similar to that of the polymer–salt complexes, and there is a strong interaction between the polymer–salt complexes and clay layers. A study of surface morphology using scanning electron microscopy reveals that microstructure of composites is affected by clay addition. Complex impedance analysis was used to calculate the bulk resistance of the composites. An enhancement in the conductivity of about one order of magnitude has been observed on 5% clay addition compared to that of the polymer–salt complexes, and it decreases monotonically for higher clay concentration. The effect of clay concentration on the structural and physical properties of polymer nanocomposites is well correlated.     

A novel PEO-based blends solid polymer electrolytes doping liquid crystalline ionomers

A novel PEO-based blends solid polymer electrolytes doping liquid crystalline ionomers (LCI), PEO/PMMA/LiClO₄/LCI, and PEO/LiClO₄/LCI were prepared by solution casting technology. Scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) analysis proved that LCI uniformly dispersed into the solid electrolytes and restrained phase separation of PEO and PMMA. Differential scanning calorimetry (DSC) results showed that LCI decreases the crystallinity of blends solid polymer electrolytes. Thermogravimetric analysis (TGA) proved LCI not only improved thermal stability of PEO/PMMA/LiClO₄ blends but also prevent PEO/PMMA from phase separation. Infrared spectra results illustrated that there exists interaction among Li⁺ and O, and LCI that promotes the synergistic effects between PEO and PMMA. The EIS result revealed that the conductivity of the electrolytes increases with LiClO₄ concentration in PEO/PMMA blends, but it increases at first and reaches maximum value of 2.53?×?10^?4 S/cm at 1.0 % of LCI. The addition of 1.0 % LCI increases the conductivity of the electrolytes due to that LCl promoting compatibility and interaction of PEO and PMMA. Under the combined action of rigidity induced crystal unit, soft segment and the terminal ionic groups in LCI, PEO/PMMA interfacial interaction are improved, the reduction of crystallinity degree of PEO leads Li⁺ migration more freely.     

Non-uniformities in polymer/liquid crystal mixtures

We theoretically model the nucleation of nematic droplets during phase ordering in mixtures of a flexible polymer and a low-molecular-weight liquid crystal. By appealing to classical nucleation theory (CNT), we calculate the energy barrier to nucleation and the size of a critical nucleus. We study the influence of a metastable intermediate phase on the nucleation of the nematic. Below a triple point in the phase diagram, there are two distinct mechanisms for the formation of a nematic nucleus: 1) direct nucleation from the isotropic phase and 2) nucleation via a precursor metastable isotropic phase. We calculate the crossover concentration as a function of temperature, delineating the regions of the phase diagram in which each mechanism prevails. In the latter case, the presence of a hidden metastable isotropic-isotropic binodal may either promote or delay the nucleation of a nematic phase. Received 9 August 2002 RID="a" ID="a"e-mail: matuyama@chem.mie-u.ac.jp     

Non-uniformities in polymer/liquid crystal mixtures

We theoretically study interfacial properties between two coexisting phases in mixtures of a flexible polymer and a low-molecular-weight liquid crystal. By numerically solving Euler equations for compositional and orientational order parameter fields, we calculate the order parameter profiles and interfacial tensions for nematic-isotropic and isotropic-isotropic phase equilibria. We find that the order parameter profiles are non-monotonic at some temperatures. The nematic-isotropic interfacial tension increases with decreasing temperature and is approximately proportional to (T - T(NI))(n) at temperatures below the nematic-isotropic transition temperature (T(NI)) of the pure nematogen. The value of the exponent n is strongly affected by the existence of a triple point.     

Characterization of pTMCnLiPF6 solid polymer electrolytes

In this study the results of our characterization of a solid polymer electrolyte based on poly(trimethylene carbonate), henceforth designated as p(TMC), and lithium hexafluorophosphate (LiPF₆) are described. Samples of solvent-free electrolytes were prepared with a range of concentration of guest salt using solvent casting from tetrahydrofuran and characterized by conductivity measurements, thermal analysis and electrochemical stability. Electrolytes based on this host polymer, with LiPF₆, were obtained as mechanically robust, flexible, transparent and completely amorphous films.     

Effect of plasticizer on structural and electrical properties of nanocomposite solid polymer electrolytes

The solid polymer electrolyte films based on polyethylene oxide, NaClO₄ with dodecyl amine modified montmorillonite as filler, and polyethylene glycol as plasticizer were prepared by a tape casting method. The effect of plasticization on structural, microstructural, and electrical properties of the materials has been investigated. A systematic change in the structural and microstructural properties of plasticized polymer nanocomposite electrolytes (PPNCEs) on addition of plasticizer was observed in our X-ray diffraction pattern and scanning electron microscopy micrographs. Complex impedance analysis technique was used to calculate the electrical properties of the nanocomposites. Addition of plasticizer has resulted in the lowering of the glass transition temperature, effective dissociation of the salt, and enhancement in the electrical conductivity. The maximum value of conductivity obtained was ∼4.4 × 10⁻⁶ S cm⁻¹ (on addition of ∼20% plasticizer), which is an order of magnitude higher than that of pure polymer nanocomposite electrolyte films (2.82 × 10⁻⁷ S cm⁻¹). The enhancement in conductivity on plasticization was well correlated with the change in other physical properties.     

Ni-MH battery based on plasticized alkaline solid polymer electrolytes

Solid-state nickel metal hydride cells were fabricated using plasticized alkaline solid polymer electrolytes (ASPE) prepared from polyvinyl alcohol (PVA), potassium hydroxide (KOH), alumina (α-Al₂O₃), and propylene carbonate (PC). The ASPE film with PVA/KOH/α-Al₂O₃/PC/H₂O weight ratio of 1.00:0.67:0.09:2.64:1.32 and conductivity of (6.6 ± 1.7) × 10⁻⁴ S cm⁻¹ was used in fabrication of the electrochemical cells. To investigate the electrochemical properties of the plasticized ASPE, cells with the configuration Mg₂Ni/plasticized ASPE/Ni(OH)₂ were fabricated. At the eighth cycle with a current drain of 0.1 mA and plateau voltage of ∼1.1 V, the discharge lasted for 14 h before the cell was considered to have failed. The failure mode of the cell was due to the formation of thin Mg(OH)₂ insulating layers.     

Effect of clay surface modification on the structure and electro-optical properties of liquid crystal/clay nanocomposites

FTIR spectroscopy, atomic force microscopy (AFM) and electro-optical measurements were used to study nanocomposites consisting of nematic liquid crystal (LC) ZLI-2293 and organophilic montmorillonite (MMT) nanoparticles. The initial MMT was modified by two different surfactants: octadecylbenzyldimethylammonium chloride (OBDM) and dioctadecylldimethylammonium chloride (DODM). According to spectroscopic results, Van der Waals interactions between the components of the LC/clay composites are stronger in OBDM-MMT case. AFM images of two types of the LC/clay nanocomposites showed different morphology consisting of large-scale structures. Correlation between the spectroscopic results and electro-optical behaviour of the LC/clay nanocomposites was observed. It was inferred that the memory effect is more pronounced for composites with OBDM-MMT due to colloid network formation, whereas the electro-optical contrast is higher for DODM-MMT, where the clay particles are not organized in any ordered structure.     

Characterisation of plasticized PMMA based solid polymer electrolytes

Polymer electrolyte films prepared from poly (methyl methacrylate) and LiAsF₆ with different concentrations of plasticizer (DBP) are described. The formation of polymer-salt complexes has been confirmed by XRD and FTIR spectral studies. The temperature dependence of the conductivity of the polymer films obeys the VTF relation. Values of conductivities of the polymer complexes are presented and discussed.     

Synthesis of star macromolecules for solid polymer electrolytes

The star macromolecules (SM) were synthesized from phloroglucinol, phosphorus oxychloride, and poly(ethylene glycol methyl ether) with different molecular weight. Structures of the products were characterized by Fourier transform infrared and ¹H-nuclear magnetic resonance. Solid polymer electrolyte films were prepared by mixing the products with poly(ethylene oxide) (PEO) and LiClO₄. The polymer blends of PEO and SM have been characterized by differential scanning calorimetry and thermogravimetry, and the polymer electrolytes have been characterized by alternating current impedance. All the SM products could improve the conductivities of the polymer electrolyte obviously at a temperature range from 20 °C to 80 °C.     

Enhancement of the electrochemical properties with the effect of alkali metal systems on PEO/PVdF-HFP complex polymer electrolytes

Polymer blend electrolytes based on poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by using different lithium salts LiX (X = ClO₄, BF₄, CF₃SO₃, and N [CF₃SO₂]₂) using solution casting technique. To confirm the structure and complexation of the electrolyte films, the prepared electrolytes were subjected to X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. Alternating current (AC) impedance analysis was performed for all the electrolyte samples at various temperatures from 303 to 343 K. The result suggests that among the various lithium salts, LiN[CF₃SO₂]₂-based electrolytes exhibited the highest ionic conductivity at 8.20 × 10^?4 S/cm. The linear variation of the ionic conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius-type thermally activated process. Activation energies were found to decrease when doping with lithium imide salt. The dielectric behavior has been analyzed using dielectric permittivity (ε*), electric modulus (M*), and dissipation factor (tanδ) of the samples. Cyclic voltammetry has been performed for the electrolyte films to study their cyclability and reversibility. Thermogravimetric and differential thermal analysis (TG/DTA) was used to ascertain the thermal stability of the electrolytes, and the porous nature of the electrolytes was identified using scanning electron microscopy via ion hopping conduction. Surface morphology of the sample having maximum conductivity was studied by an atomic force microscope (AFM).     

Effect of nanochitosan on electrochemical, interfacial and thermal properties of composite solid polymer electrolytes

PEO-based solid polymer electrolyte films with various concentrations of nanochitosan as filler and LiCF₃SO₃ as salt were prepared by membrane hot-press technique. Nanochitosan was prepared from chitosan by conventional chemical cure method. The prepared composite membranes were characterized by FT-IR, XRD, thermal, SEM, AFM analyses, electrochemical impedance spectroscopy, cyclic voltammetry and compatibility studies. The ionic conductivity and thermal stability of the polymer membranes were enhanced significantly by addition of nanofiller. The compatibility studies reveal that filler incorporated membrane is better compatible with lithium interface than filler free electrolyte.     

Effect of radiation on conductivity of solid PVA–KOH–PC composite polymer electrolytes

The aim of this work is to enhance the room temperature conductivity of solid alkaline composite polymer electrolytes (ACPEs) based on polyvinyl alcohol/potassium hydroxide/propylene carbonate (PVA–KOH–PC) composites by cross-linking the PVA and bond scission of the PC by γ-radiation. The ACPEs were prepared by solvent-casting technique and irradiated with doses up to 200 kGy at room temperature. The microstructure of the ACPEs was measured using XRD spectrometer, and the results show the structural change from semicrystalline to amorphous, indicating that the cross-linking has been achieved at higher doses. It was found that the PKOH composite at 40 wt% KOH and PPC composite at 60 wt% PC show higher conductivities. The conductivity of the PKPC composites is dominated by dc conductivity at higher frequencies and that PC with 60 wt% has the highest conductivity at a dose of 200 kGy.Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6–8, 2005.     

低散射非偏振依赖的聚合物/液晶光栅

了降低聚合物/液晶光栅的散射损失,并消除光栅的偏振依赖性,选取了低官能度的光敏单体作为反应体系,并逐步提高光栅的制备温度。首先选用五官能度的DPHPA （dipentaerythritol hydroxyl pentaacrylate）、双官能度的PDDA（ phthalic diglycol diacrylate）以及单官能度的NVP （N-vinylpyrrolidone）作为反应体系;其次,在制备过程中在光栅的后面放置加热台,逐步提升制备温度。实验结果表明:当制备温度上升到62 ℃以上,光栅有更多（36%）的液晶析出,相分离比常温下制备时要更完全一些,而且高温下制备的光栅其平整度更高,从而使光栅的散射损失比常温下减小了66.7%,器件的SEM图片也进一步证明了这个结论。同时高温制备也消除了液晶光栅的偏振依赖特性。     

Structural and ionic conductivity of PEO blend PEG solid polymer electrolyte

Structural and ionic conductivity of PEO blend PEG with KI solid polymer electrolyte system is presented. The polymer PEG showed miscible with the high molecular weight polymer PEO. The X-ray diffraction patterns of PEO/PEG with KI salt indicated the decrease in the degree of crystallinity with increasing concentration of the salt. The DSC measurements of PEO/PEG:KI polymer electrolyte system showed that the melting temperature is shifted towards the lower temperature with increase of the salt concentration. Optical micrographs demonstrated that the spherulites of different sizes are present along with dark regions between the spherulites for lower salt compositions. With increase of salt concentration more amorphous regions are observed. The significance of blend is the increase of one order in ionic conductivity when compared to without blend PEO electrolyte.     

Effects of compositions on properties of PEO–KI–I2 salts polymer electrolytes for DSSC

The effects of compositions on properties of PEO/KI/I₂ salts polymer electrolytes were investigated to optimize the photovoltaic performance of solid state DSSCs. XRD pattern for the mole ratio 12:1 of [EO:KI] was showed the formation of complete amorphous complex. DSC results also confirmed the amorphous nature of the polymer electrolyte. The highest value of ionic conductivity is 8.36 × 10^− 5 S/cm at 303 K (ambient temperature) and 2.32 × 10^− 4 S/cm at 333 K (moderate temperature) for the mole ratio 12:1 of EO:KI complex. The effect of contribution of [I⁻] and [I₃⁻] concentration with conductivity were also evaluated. FTIR spectrum reveals that the alkali metal cations were co-ordinated to ether oxygen of PEO. The formation of polyiodide ions, such as symmetric I₃⁻ (114 cm^− 1) and I₅⁻ (145 cm^− 1) caused by the addition of iodine was confirmed by FT Raman spectroscopic measurements. The optimum composition of PEO–KI–I₂ polymer electrolyte system for higher conductivity at ambient and moderate temperatures was reported. A linear Arrhenius type behaviour was observed for all the PEO–KI polymer complexes. Transport number measurements were carried out for several polymer electrolyte compositions. Dye-sensitized solar cells were fabricated by using higher conductivity polymer electrolyte compositions and its photoelectrochemical performance was investigated. The fill factor, short-circuit current, photovoltage and energy conversion efficiency of the DSSC assembled with optimized electrolyte composition were calculated to be 0.563, 6.124 mA/cm², 593 mV and 2.044% respectively.     

Ionic conductivity studies in composite solid polymer electrolytes based on methylmethacrylate

The preparation and characterization of composite polymer electrolytes of PMMA-LiClO₄-DMP for different concentrations of CeO₂ have been investigated. FTIR studies indicate complex formation between the polymer, salt and plasticizer. The electrical conductivity values measured by a.c. impedance spectroscopy are found to depend upon the CeO₂ concentration. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and the results are discussed.     

Study on ammonium acetate salt-added polyvinyl alcohol-based solid proton-conducting polymer electrolytes

Polyvinyl alcohol (PVA) complexes with different compositions of ammonium acetate (AA) are prepared by solution cast technique. Polyvinyl alcohol crystallinity decreased with increasing ammonium acetate salt content. Molecular weight and density of polyvinyl alcohol complex increased with the addition of ammonium acetate salt. The ammonium acetate salt addition resulted in plasticization and hence decreased glass transition temperature (T _g) as well as hardness number (HV). 80PVA:20AA presented maximum conductivity (σ?=?1.3?×?10^?7S cm^?1 at 303 K) with minimum activation energy (E _a) 0.151 eV below the T _g. The proton transport number determined using EMF method found ≈0.98 for polymer complex with ammonium acetate content >15 mol%. The complex impedance is measured as a function of frequency, temperature, relative humidity, and hydrogen partial pressure. Enhanced bulk conductivity with increased H₂ partial pressure and relative humidity suggested H⁺ mobility within complex polymer electrolyte.     

Preparation and characterization of solid polymer electrolytes based on PHEMO and PVDF-HFP

Polymer electrolyte membranes consisting of a novel hyperbranched polyether PHEMO (poly(3-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy}methyl-3′-methyloxetane)), PVDF-HFP (poly(vinylidene fluoride-hexafluoropropylene)) and LiTFSI have been prepared by solution casting technique. X-ray diffraction of the PHEMO/PVDF-HFP polymer matrix and pure PVDF-HFP revealed the difference in crystallinity between them. The effect of different amounts of PVDF-HFP and lithium salts on the conductivity of the polymer electrolytes was studied. The ionic conductivity of the prepared polymer electrolytes can reach 1.64 × 10^? 4 S·cm^? 1 at 30 °C and 1.75 × 10^? 3 S·cm^? 1 at 80 °C. Thermogravimetric analysis informed that the PHEMO/PVDF-HFP matrix exhibited good thermal stability with a decomposition temperature higher than 400 °C. The electrochemical experiments showed that the electrochemical window of the polymer electrolyte was around 4.2 V vs. Li⁺/Li. The PHEMO/PVDF-HFP polymer electrolyte, which has good electrochemical stability and thermal stability, could be a promising solid polymer electrolyte for polymer lithium ion batteries.