Ionic conductivity, thermal stability and FT-IR studies on plasticized PVC / PMMA blend polymer electrolytes complexed with LiAsF6 and LiPF6

The lithium salt (x) (x=LiAsF₆, LiPF₆) was complexed with a blend of poly(vinyl chloride) (PVC) / poly(methyl methacrylate)(PMMA) and plasticized with a combination of ethylene carbonate(EC) and propylene carbonate(PC). The electrolyte films were prepared using doctor blade method and subjected to ionic conductivity measurements at nine different temperatures viz.,-30, -15, 0, 15, 30, 40, 50, 60 and 70 °C. The films were also subjected to TG - DTA and FT-IR analysis. The effect of salt on ionic conductivity is discussed. A 75:25 PMMA/PVC blend at 60 % plasticizer content has been found to possess optimal properties in terms of ionic conductivity, thermal and electrochemical stability.     

Electrical,structural, and morphological studies of honeycomb-like microporous zinc-ion conducting poly (vinyl chloride)/poly (ethyl methacrylate) blend-based polymer electrolytes

Solid polymer electrolytes (SPEs) based on poly (vinyl chloride)/poly (ethyl methacrylate) [PVC/PEMA] blend complexed with zinc triflate [Zn(CF₃SO₃)₂] salt have been prepared using solution casting technique. Thin film samples containing various blend ratios of PVC/PEMA with fixed composition of salt have been examined by means of complex impedance analysis, and as a consequence, the typical composition corresponding to PVC (30 wt%)/PEMA (70 wt%) has been identified as the optimized blend exhibiting the highest room temperature ionic conductivity of 10^?8 Scm^?1. The ionic conductivity of the optimized blend was further enhanced from 10^?8 to 10^?6 Scm^?1 by adding the chosen salt in different weight percentages at 301 K. The occurrence of complexation of the polymer blend and an evidence of interaction of cations, namely Zn²⁺ ions with the polymer blend, have been confirmed by Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy measurement studies. The efficacy of ion-polymer interactions was estimated by means of an evaluation of transport number data pertaining to Zn²⁺ ions which was found to be 0.56. The apparent changes resulting in the structural properties of these polymer electrolytes possessing a honeycomb-like microporous structure were identified using X-ray diffraction (XRD) and scanning electron microscopic (SEM) studies. Such promising features of the present polymer blend electrolyte system appear to suggest possible fabrication of new rechargeable zinc batteries involving improved device characteristics.     

Rheological properties and impedance spectroscopy of PMMA-PVdF blend and PMMA gel polymer electrolytes for advanced lithium batteries

In the present study, blend ionic conducting membranes formed by poly(methylmethacrylate (PMMA) / poly(vinilydenefluoride) (PVDF) (blend ratio PMMA/PVdF=80/20), lithium perchlorate (LiClO₄) as a salt and a mixture of ethylene carbonate (EC)-propylene carbonate (PC) as plasticizer are prepared and characterized by impedance spectroscopy and dynamic rheological experiments. We compared the results obtained on the blends with those on PMMA gel-based polymer electrolytes incorporating the same EC/PC mixture of plasticizer and the same quantities of salt. The main focus of this study is to illustrate the rheological data of the gels and blends electrolytes to point up their mechanical stability with the temperature in sight of the technological application. The conductivity values are reported in the 20–100 °C temperature range for different lithium salt contents, while the rheological behaviour has been recorded up to 140 °C. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Increase of photoluminescence from fullerenes-doped poly (alkyl methacrylate) under laser irradiation

Increase of photoluminescence (PL) from fullerenes (C₆₀ and C₇₀)-doped poly(alkyl methacrylate), such as poly(ethyl methacrylate) (PEMA), poly(isopropyl methacrylate) (PiPMA) and poly(isobutyl methacrylate) (PiBMA), have been studied under laser irradiation with wavelength of in air. After laser irradiation, PL peaks of all fullerenes doped-polymers are broadened and blue-shifted. This PL increase depends on the fullerene concentrations. By comparing with fullerenes-doped PMMA, fullerenes-doped PEMA have the greatest PL increase among the four kinds of polymers, including PEMA, PiPMA, PiBMA and PMMA. PL intensity of C₇₀-doped polymers increases much more quickly than the corresponded C₆₀-doped polymers at the initial stage of laser irradiation. Great change on their UV-visible absorption spectra before and after laser irradiation indicate some great variation on chemical structure of fullerene molecules dispersed in polymer matrix under laser irradiation. This great PL increase may be attributed to formation of fullerene oxide-polymer and oxidized fullerene-polymer adducts due to laser-induced photochemical reactions among fullerene, oxygen and polymer.     

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.     

Investigation of dibutyl phthalate as plasticizer on poly(methyl methacrylate)–lithium tetraborate based polymer electrolytes

Polymer electrolyte membranes, comprising of poly(methyl methacrylate) (PMMA), lithium tetraborate (Li₂B₄O₇) as salt and dibutyl phthalate (DBP) as plasticizer were prepared using a solution casting method. The incorporation of DBP enhanced the ionic conductivity of the polymer electrolyte. The polymer electrolyte containing 70 wt.% of poly(methyl methacrylate)–lithium tetraborate and 30 wt.% of DBP presents the highest ionic conductivity of 1.58 × 10⁻⁷ S/cm. The temperature dependence of ionic conductivity study showed that these polymer electrolytes obey Vogel–Tamman–Fulcher (VTF) type behaviour. Thermogravimetric analysis (TGA) was employed to analyse the thermal stability of the polymer electrolytes. Fourier transform infrared (FTIR) studies confirmed the complexation between poly(methyl methacrylate), lithium tetraborate and DBP.     

无规共聚物与均聚物共混体系的相容性

用核磁共振方法(NMR)及差示扫描量热法(DSC)测定了苯乙烯-丙烯腈(SAN)无规共聚物与均聚物系列聚甲基丙烯酸甲酯(PMMA),聚甲基丙烯酸乙酯(PEMA),聚甲基丙烯酸正丁酯(PnBMA),聚甲基丙烯酸异丁酯(PiBMA)共混体系的有关参数,比较全面地研究了影响SAN与聚甲基丙烯酸酯类(PMAs)相容性的因素,对它们相容性的本质进行了探讨,得出了一些重要结论.     

Effect of lithium salt concentration in PVAc/PMMA-based gel polymer electrolytes

Hybrid solid polymer electrolyte films comprising of poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), LiClO₄, and propylene carbonate are prepared by solution casting technique by varying the salt concentration. In this study, PVAc/PMMA polymer blend ratio is fixed as 25:75 on the basis of conductivity and mechanical stability of the film. X-ray diffraction, Fourier transform infrared impedance, thermogravimetry/differential thermal analysis and scanning electron microscopy studies are carried out for the polymer electrolytes. The maximum ionic conductivity is found to be 4.511 × 10⁻⁴ S cm⁻¹ at 303 K for the plasticized polymer electrolyte with 8 wt.% of LiClO₄. The ionic conductivity is found to decrease with an increase of LiClO₄ concentration.     

Effect of molecular weight of PMMA on the conductivity and viscosity behavior of polymer gel electrolytes containing NH<Subscript>4</Subscript>CF<Subscript>3</Subscript>SO<Subscript>3</Subscript>

The addition of polymethyl methacrylate (PMMA) having different molecular weights to electrolytes containing ammonium trifluoromethanesulfonate (NH₄CF₃SO₃) in diethyl carbonate (DEC) has been found to result in conductivity enhancement and to yield gel electrolytes with conductivity higher than the corresponding liquid electrolytes. The increase in conductivity has been found to be due to the dissociation of undissociated NH₄CF₃SO₃ and ion aggregates present in the electrolytes, and this has been supported by Fourier transform infrared spectroscopy results, which suggests active interaction of PMMA and NH₄CF₃SO₃ in these gel electrolytes. The increase in conductivity also depends upon the molecular weight of the polymer used and is relatively more for PMMA having lower molecular weight. The increase in viscosity with PMMA addition also depends upon the molecular weight of the polymer and is closely related to the conductivity behavior of these electrolytes. Polymer gel electrolytes have been found to be thermally stable up to a temperature of 125 °C.     

MnO2-polypyrrole conducting polymer composite electrodes for electrochemical redox supercapacitors

Redox supercapacitors using electrochemically synthesised MnO₂-polypyrrole composite electrodes have been fabricated with different electrolytes, namely polymer electrolyte film (polyvinyl alcohol, PVA-H₃PO₄ aqueous blend), aprotic liquid electrolyte (LiClO₄-propylene carbonate, PC) and polymeric gel electrolyte [poly methyl methacrylate, (PMMA)-Ethylene carbonate (EC)-Propylene carbonate (PC)-NaClO₄]. The capacitors have been characterised using galvanostatic charge-discharge methods. The cell with aqueous PVA-H₃PO₄ shows non-capacitive behaviour owing to some reversible chemical reaction of MnO₂ with water while the MnO₂-polypyrrole composite is found to be a suitable electrode material for redox supercapacitors with aprotic (non-aqueous) electrolytes. The solid state supercapacitor based on MnO₂-polypyrrole composite electrodes with gel electrolyte gives stable values of capacitance of 10.0–18.0 mF cm⁻² for different discharge current densities.     

Characterization of high ionic conducting PVAc–PMMA blend-based polymer electrolyte for electrochemical applications

A solid polymer blend electrolyte is prepared using poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) polymers with different molecular weight percentage (wt%) of ammonium thiocyanate (NH₄SCN) by solution casting technique with tetrahydrofuran (THF) as a solvent. The structural, morphological, vibrational, thermal and electrical properties of the prepared polymer blend electrolytes have been studied. The incorporation of NH₄SCN into the polymeric matrix causes decrease in the degree of crystallinity of the samples. The complex formation between the polymer and salt has been confirmed by FTIR technique. The increase in T _g with increase in salt concentration has been investigated. The maximum conductivity of 3.684?×?10^?3 S cm^?1 has been observed for the composition of 70PVAc/30PMMA/30 wt% of NH₄SCN at 303 K. This value of ionic conductivity is five orders of magnitude greater than that of 70PVAc/30PMMA polymer membrane. Dielectric and transport studies have been done. The highest conducting polymer electrolyte is used to fabricate proton battery with the configuration Zn/ZnSO₄·7H₂O (anode) ||polymer electrolyte||PbO₂/V₂O₅ (cathode). The open circuit voltage of the fabricated battery is 1.83 V, and its performance has been studied.     

Investigation on the effects of addition of SiO<Subscript>2</Subscript> nanoparticles on ionic conductivity,FTIR, and thermal properties of nanocomposite PMMA–LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>

Composite polymer electrolyte systems composed of poly(methyl methacrylate) (PMMA) as the host polymer, lithium trifluoromethanesulphonate (also known as lithium triflate; LiCF₃SO₃) as dopant salt, and a variety of different concentrations of nano-sized fumed silica (SiO₂) as inorganic filler were studied. The effect upon addition of SiO₂ on the ionic conductivity of the composite polymer electrolytes was investigated, and it was proven that the ionic conductivity had been enhanced. In addition, the interfacial stability also showed improvement. Maximum conductivity was obtained upon addition of 2 wt.% SiO₂. The complexation of PMMA and LiCF₃SO₃ was verified through Fourier transform infrared studies. The thermal stability of the polymer electrolytes was also found to improve after dispersion of inorganic filler. This was proven in the thermogravimetric studies.     

Experimental investigations on plasticized PMMA/PVA polymer blend electrolytes

Blend based polymer electrolytes composed of poly (methyl methacrylate) (PMMA), poly(vinylalcohol) (PVA) and LiClO₄ are prepared using solvent casting technique. The polymer films are characterized by XRD and FTIR studies to determine the molecular environment for the conducting ions. These polymer films have been investigated in terms of ionic conductivity using the results of impedance studies. The influence of the blend composition on the electrochemical behaviour is also discussed. The highest room temperature conductivity obtained for the film consisting of PMMA, PVA, LiClO₄ and DMP is 0.06×10⁻³ S/cm at 303 K. The PMMA-PVA blend based polymer electrolytes look very desirable and promising for lithium battery applications.     

Mechanical spectroscopy of laser deposited polymers

Pulsed laser deposition (PLD) at 248 nm in ultra high vacuum was used to produce thin poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) films. The ablation and deposition mechanisms were found to be similar in both systems. Having the same backbone, these polymers differ in the size of their polar side groups leading to changes in their dynamics. Studies of the relaxation processes were performed using mechanical torsion and bending spectroscopy by means of a double-paddle oscillator (DPO) and an in-situ plasma plume excited reed (PPXR), respectively. A strong increase of the mechanical damping was observed during annealing of the polymer films well above the glass transition temperature T _g, while in-situ X-ray measurements did not reveal any structural changes. For PEMA, the glass transition temperature T _g=335 K and the main absorption maximum appear at lower temperatures compared to PMMA (T _g=380 K), allowing one to measure the mechanical properties in a much wider range above T _g.     

Effects of plasticizer and nanofiller on the dielectric dispersion and relaxation behaviour of polymer blend based solid polymer electrolytes

Solid polymer electrolytes consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50:50 wt/wt%) with lithium triflate (LiCF₃SO₃) as a dopant ionic salt at stoichiometric ratio [EO + (CO)]:Li⁺ = 9:1, poly(ethylene glycol) (PEG) as plasticizer (10 wt%) and montmorillonite (MMT) clay as nanofiller (3 wt%) have been prepared by solution cast followed by melt–pressing method. The X–ray diffraction study infers that the (PEO–PMMA)–LiCF₃SO₃ electrolyte is predominantly amorphous, but (PEO–PMMA)–LiCF₃SO₃–10 wt% PEG electrolyte has some PEO crystalline cluster, whereas (PEO–PMMA)–LiCF₃SO₃–10 wt% PEG–3 wt% MMT electrolyte is an amorphous with intercalated and exfoliated MMT structures. The complex dielectric function, ac electrical conductivity, electric modulus and impedance spectra of these electrolytes have been investigated over the frequency range 20 Hz to 1 MHz. These spectra have been analysed in terms of the contribution of electrode polarization phenomenon in the low frequency region and the dynamics of cations coordinated polymer chain segments in the high frequency region, and also their variation on the addition of PEG and MMT in the electrolytes. The temperature dependent dc ionic conductivity, dielectric relaxation time and dielectric strength of the plasticized nanocomposite electrolyte obey the Arrhenius behaviour. The mechanism of ions transportation and the dependence of ionic conductivity on the segmental motion of polymer chain, dielectric strength, and amorphicity of these electrolytes have been explored. The room temperature ionic conductivity values of the electrolytes are found ∼10⁻⁵ S cm⁻¹, confirming their use in preparation of all-solid-state ion conducting devices.     

Kinetics of sono-photooxidative degradation of poly(alkyl methacrylate)s

The mechano-chemical degradation of poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(n-butyl methacrylate) (PBMA) using ultrasound (US), ultraviolet (UV) radiation and a photoinitiator (benzoin) has been investigated. The degradation of the polymers was monitored using the reduction in number average molecular weight (M(n)) and polydispersity (PDI). A degradation mechanism that included the decomposition of the initiator, generation of polymer radicals by the hydrogen abstraction of initiator radicals, reversible chain transfer between stable polymer and polymer radicals was proposed. The mechanism assumed mid-point chain scission due to US and random scission due to UV radiation. A series of experiments with different initial M(n) of the polymers were performed and the results indicated that, irrespective of the initial PDI, the PDI during the sono-photooxidative degradation evolved to a steady state value of 1.6±0.05 for all the polymers. This steady state evolution of PDI was successfully predicted by the continuous distribution kinetics model. The rate coefficients of polymer scission due to US and UV exhibited a linear increase and decrease with the size of the alkyl group of the poly(alkyl methacrylate)s, respectively.     

Electrochemical studies on polymer electrolytes based on poly(methyl methacrylate)-grafted natural rubber for lithium polymer battery

MG30 is natural rubber grafted with 30% poly(methyl methacrylate). Gel polymer electrolytes containing MG30–LiCF₃SO₃–X (X = propylene carbonate, ethylene carbonate) are prepared by solution casting technique. The polymer–salt complexes were investigated using Fourier-transformed infrared. The ionic conductivity of the electrolytes are determined by the ac impedance studies over the temperature range of 303–383 K and is observed to obey the Vogel–Tamman–Fulcher (VTF) rule. The Li⁺ transference number obtained using the Bruce and Vincent method is <0.3. The Li/Li⁺ interface stability is established and the electrolytes were found to be able to withstand a voltage of more than 4.2 V.     

Dielectric properties and fluctuating relaxation processes of poly(methyl methacrylate) based polymeric nanocomposite electrolytes

Solid polymer nanocomposite electrolytes (SPNEs) consisted of poly(methyl methacrylate) (PMMA) and lithium perchlorate (LiClO₄) of molar ratio C=O:Li⁺=4:1 with varying concentration of montmorillonite (MMT) clay as nanofiller have been prepared by classical solution casting and high intensity ultrasonic assisted solution casting methods. The dielectric/electrical dispersion behaviour of these electrolytes was studied by dielectric relaxation spectroscopy at ambient temperature. The dielectric loss tangent and electric modulus spectra have been analyzed for relaxation processes corresponding to the side groups rotation and the segmental motion of PMMA chain, which confirm their fluctuating behaviour with the sample preparation methods and also with change of MMT concentration. The feasibility of these relaxation fluctuations has been explained using a transient complex structural model based on Lewis acid–base interactions. The low permittivity and moderate dc ionic conductivity at ambient temperature suggest the suitability of these electrolytes in fabrication of ion conducting electrochromic devices and lithium ion batteries. The amorphous behaviour and the exfoliated/intercalated MMT structures of these nanocomposite electrolytes were confirmed by X-ray diffraction measurements.     

Dielectric and thermal features of zinc ion conducting gel polymer electrolytes (GPEs) containing PVC / PEMA blend and EMIMTFSI ionic liquid

A new series of gel polymer electrolytes (GPEs) based on an optimized composition of polymer blend-salt matrix [poly(vinyl chloride) (PVC) (30 wt%) / poly(ethyl methacrylate) (PEMA) (70 wt%): 30 wt% zinc triflate Zn(CF₃SO₃)₂] containing different concentrations of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) ionic liquid has been prepared by simple solution casting technique. The prepared films of gel polymer membranes have been characterized utilizing complex impedance spectroscopy, differential scanning calorimetry (DSC), thermogravimetric (TG), and cyclic voltammetry (CV) analyses. The dielectric constant and ionic conductivity pursue similar trend with increasing EMIMTFSI concentration. The addition of ionic liquid in varied amounts into the optimized polymer blend-salt system effectively reduces the glass transition temperature (T_g) of the film as revealed from differential scanning calorimetry results. The origin of an improved thermal stability and feasible cyclic performance in respect of the best conducting sample of the resultant gel polymer electrolytes was also examined by utilizing thermogravimetric and cyclic voltammetry measurements.     

Effect of ethylene carbonate concentration on structural and electrical properties of PEO–PMMA polymer blends

Polyethylene oxide–polymethyl methacrylate (PEO–PMMA) polymer blend electrolyte system complexed with silver salt having different ethylene carbonate (EC) concentrations was prepared using solution cast technique. Complex formation and change in structural and microstructural properties have been studied by X-ray diffraction, Fourier transform infrared, and scanning electron microscopy analysis. The thermal properties of polymer films have been examined by the differential scanning calorimetry technique. Addition of plasticizer is observed to lower melting temperature. Electrical response of polymer films has been measured as a function of EC concentration and temperature using complex impedance spectroscopy. Complex impedance data are used to analyze the conductivity, permittivity, and modulus formalism to understand the conduction mechanism. The temperature dependence of electrical conductivity of polymer electrolytes shows a sudden rise at the melting temperature of PEO.