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.     

Ionic conductivity studies in PMMA/PVdF polymer blend electrolyte with lithium salts

Batteries using ionically conducting polymer membranes as electrolytes are very attractive, since the concept of power sources capable of combining a high energy content with plasticity is very appealing for the consumer electronics market and in electric vehicle applications. Blend based polymer electrolytes composed of poly (methylmethacrylate) (PMMA), Poly Vinylidene fluoride (PVdF), Lithium salt (LiX) (X=ClO₄, BF₄ and CF₃SO₃) and Dimethyl Phthalate (DMP) are prepared using solvent casting technique. The films have been characterized using XRD, FTIR, Thermal and SEM studies; the effect of complexing salt and temperature on ionic conductivity is also discussed. The maximum conductivity value obtained for the solid polymer electrolyte film at 303 K is 4.2 × 10⁻³ S/cm.     

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.     

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.     

Role of salt concentration on conductivity optimization and structural phase separation in a solid polymer electrolyte based on PMMA-LiClO4

Although a large number of ionic conductors based on poly(methyl-methacrylate) (PMMA) are reported in literature, an optimization of salt concentration with respect to conductivity and stability properties remains by and large neglected. We report, perhaps for the first time, such an optimization of salt (LiClO₄) concentration on structural, morphological, electrical, and ion–polymer interaction in PMMA-based solid polymer films. The active coordination site for the cation (Li⁺), out of the two possible electron donating functional groups (i.e. C=Ö and Ö–CH₃) in PMMA, has been ascertained on the basis of evidences recorded in Fourier transform infrared spectrum. The results suggested C=Ö as the only possible site in PMMA matrix for coordination with Li⁺ cation. The X-ray diffraction results have clearly indicated an optimum limit of salt dissolution in PMMA matrix corresponding to O/Li = 4 (i.e., ~21wt.%) above which “phase-separation” occurs distinctly. The effect of salt concentration on amorphous → crystalline phase changes in PMMA and its correlation to morphology have been clearly observed in terms of their impact on electrical properties. An optimum electrical conductivity of ~7.2 × 10^?5S cm^?1 has been recorded at 100°C (~PMMA glass transition). The temperature dependence of conductivity follows typical Vogel–Tamman–Fulcher behavior.     

Preparation and characterization of biodegradable poly(ε-caprolactone)-based gel polymer electrolyte films

Biodegradable polymer electrolyte films based on poly(ε-caprolactone) (PCL) in conjunction with lithium tetrafluoroborate (LiBF₄) salt and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄) ionic liquid were prepared by solution cast technique. The structural, morphological, thermal, and electrical properties of these films were examined using X-ray diffraction (XRD), optical microscopy (OM), differential scanning calorimetry (DSC), and impedance spectroscopy. The XRD and OM results reveal that the pure PCL possesses a semi-crystalline nature and its degree of crystallinity decreases with the addition of LiBF₄ salt and EMIMBF₄ ionic liquid. DSC analysis indicates that the melting temperature and enthalpy are apparently lower for the 40 wt% EMIMBF₄ gel polymer electrolyte as compared with the others. The ambient temperature electrical conductivity increases with increasing EMIMBF₄ concentration and reaches a high value of ～2.83?×?10^?4 S cm^?1 for the 85 PCL:15 LiBF₄ + 40 wt% EMIMBF₄ gel polymer electrolyte. The dielectric constant and ionic conductivity follow the same trend with increasing EMIMBF₄ concentration. The dominant conducting species in the 40 wt% EMIMBF₄ gel polymer electrolyte determined by Wagner’s polarization technique are ions. The ionic conductivity of this polymer electrolyte (～2.83?×?10^?4 S cm^?1) should be high enough for practical applications.     

AC impedance, FTIR and XRD investigations of poly acrylonitrile complexed with LiCF3SO3

Solid polymer electrolytes of high ionic conductivity are prepared using poly acrylonitrile (PAN), propylene carbonate (PC), ethylene carbonate (EC) and LiCF₃SO₃. The polymer films are characterised by X-ray diffraction, FTIR and a.c. impedance spectroscopic techniques. The conductivity studies of PAN-LiCF₃SO₃-PC-EC polymer electrolyte systems are carried out in the temperature range 301–373 K. The temperature dependence of the conductivity of the polymer films obeys the VTF relation. The conductivity values are presented and the results are discussed.     

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.     

Effect of ionic liquid incarceration during free radical polymerization of PMMA on its structural and electrical properties

The thin film of poly(methyl methacrylate) (PMMA) has been widely studied as host in a polymer electrolyte system due to its good mechanical stability towards lithium electrode. However, the brittle property of this film creates additional resistance for the ionic conduction. The addition of ionic liquid (IL) has been noticed to improve the brittleness of the film. In addition, its ionic conductivity can also be enhanced, but no free standing film can be obtained when higher amount of IL was added. Therefore, in this study, 1-methyl-3-pentamethyldisiloxymethylimidazolium bis(trifluoromethylsulfonyl)imide,[(SiOSi)C₁C₁im][NTf₂], was incarcerated during free radical polymerization of MMA. Interestingly, this newly synthesized PMMA (PMMA_IL) gives a flexible and transparent film with ionic conductivity of ～10^?7 S/cm at room temperature. The structural properties of this PMMA_IL were further investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and optical microscope (OM).     

Electrical and electrochemical properties of poly (methyl methacrylate) based nanocomposite gel electrolytes dispersed with dedoped (insulating) polyaniline nanofibers

In this work, we have investigated the effect of dedoped (insulating) polyaniline (PAni) nanofibers on the electrical and electrochemical properties of poly(methyl methacrylate) (PMMA)-based gel electrolytes. PAni nanofibers have been synthesized using interfacial polymerization technique. By analysis of X-ray diffraction (XRD) and impedance spectroscopy results, it has been demonstrated that the incorporation of dedoped PAni nanofibers up to a moderate concentration (4 wt%) to PMMA–(PC?+?DEC)–LiClO₄ gel polymer electrolyte system significantly enhances the ionic conductivity of the electrolyte system, which can be attributed to the inhibition of polymer chain reorganization upon dispersion of high aspect ratio nanofibers in PMMA matrix resulting in reduction in polymer crystallinity, which gives rise to an increase in ionic conductivity. At higher concentration, dedoped nanofibers appear to get phase separated and form insulating clusters, which impede ionic transport. The phase separation phenomena at higher fraction of nanofibers are confirmed by XRD. Studies on electrochemical behavior reveal that electrochemical potential window increases with the increase of nanofibers loading.     

Correlation Between Segmental Dynamics,Glass Transition,and Lithium Ion Conduction in Poly(Methyl Methacrylate)/Ionic Liquid Mixture

A solid-state membrane of a polymer/ionic liquid miscible mixture, poly(methyl methacrylate) (PMMA) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) doped with lithium perchlorate (LiClO₄), was prepared and characterized. Miscibility, segmental dynamics, glass transition and ionic conductivity were investigated. Based on the results from differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), the system is fully miscible and of single phase. Broadening of the glass transition was observed when increasing the amount of ionic liquid, which can be attributed to mobility and flexibility differences between the polymer and ionic liquid. A large dynamical asymmetry and intrinsic mobility difference allow segmental and structural motion/relaxation over a wider temperature range by increasing the amount of ionic liquid. Saturation recovery spin–lattice relaxation time (T₁) versus temperature obtained from ⁷Li nuclear magnetic resonance (NMR) showed high mobility of lithium ions, which was almost temperature independent. Lithium ion conductivity significantly increases with increasing ionic liquid amount. It is concluded that lithium ion mobility and its conduction is positively correlated to segmental dynamics of ion carriers in this model system, which is more noticeable in mixtures with higher amounts of the ionic liquid.     

Electrical,optical, and structural characterization of polymer blend (PVC/PMMA) electrolyte films

Ion-conducting solid polymer blend electrolytes based on polyvinyl chloride (PVC)/poly methyl methacrylate (PMMA) complexed with sodium perchlorate (NaClO₄) were prepared in various concentrations by solution cast technique. The features of complexation of the electrolytes were studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. DC conductivity of the films was measured in the temperature range 303–398 K. Transference number measurements were carried out to investigate the nature of charge transport in the polymer blend electrolyte system. The electrical conductivity increased with increasing dopant concentration, which is attributed to the formation of charge transfer complexes. The polymer complexes exhibited Arrhenius type dependence of conductivity with temperature. In the temperature range studied, two regions with different activation energies were observed. Transference number data showed that the charge transport in this system is predominantly due to ions. Optical properties like absorption edge, direct band gap, and indirect band gap were estimated for pure and doped films from their optical absorption spectra in the wavelength region 200–600 nm. It was found that the energy gap and band edge values shifted to lower energies on doping with NaClO₄ salt. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamil Nadu, India, Dec. 7–9, 2006.     

Characterization of blend polymer PVA-PVP complexed with ammonium thiocyanate

Thin films of blend polymer electrolytes comprising poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) complexed with ammonium thiocyanate (NH₄SCN) salt in different compositions have been prepared by solution casting technique using distilled water as solvent. The prepared films have been investigated by different experimental techniques. The complexation of these films has been studied by FTIR spectroscopy. The increase in amorphousness of the films with increase in NH₄SCN content has been confirmed by XRD analysis. The addition of ammonium thiocyanate salt to PVA-PVP polymer blend shows a shift in T_g of the blend. The effect of salt concentration and temperature on the ionic conductivity of the polymer blend films has been analyzed using AC impedance spectroscopy. The maximum conductivity of 6.85 × 10^?4 S cm^?1 at room temperature has been observed for the blend with 50 mol% PVA-50 mol% PVP complexed with 40 mol% NH₄SCN. The activation energy has been found to be minimum (0.24 eV) for this sample. Wagner’s polarization technique shows that the charge transport in these blend films is predominantly due to ions. Using the highest conductivity blend polymer electrolyte, a proton battery has been fabricated and its discharge characteristics have been studied.     

The physical and electrochemical properties of poly(vinylidene chloride-co-acrylonitrile)-based polymer electrolytes prepared with different plasticizers

Lithium ion-conducting membranes with poly(ethylene oxide) (PEO)/poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN)/lithium perchlorate (LiClO₄) were prepared by solution casting method. Different plasticizers ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (gBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dibutyl phthalate (DBP) were complexed with the fixed ratio of PEO/PVdC-co-AN/LiClO₄. The preparation and physical and electrochemical properties of the gel polymer electrolytes have been briefly elucidated in this paper. The maximum ionic conductivity value computed from the ac impedance spectroscopy is found to be 3?×?10^?4 S cm^?1 for the EC-based system. From DBP-based system down to EC-based system, a decrease of crystallinity and an increase of amorphousity are depicted by X-ray diffraction technique, the decrease of band gap energy is picturized through UV–visible analysis, the decrease of glass transition temperature is perceived from differential scanning calorimetry plots, and the reduction of photoluminescence intensity is described through photoluminescence spectroscopy study at an excitation wavelength of 280 nm. Atomic force microscopic images of EC-based polymer electrolyte film show the escalation of micropores. Fourier transform infrared spectroscopy study supports the complex formation and the interaction between the polymers, salt, and plasticizer. The maximum thermal stability is obtained from thermogravimetry/differential thermal analysis, which is found to be 222 °C for the sample complexed with EC. The cyclic voltagram of the sample having a maximum ionic conductivity shows a small redox current at the anode, and cathode and the chemical stability is confirmed by linear sweep voltammetry.     

Effect of dibutyl phthalate as plasticizer on high-molecular weight poly(vinyl chloride)–lithium tetraborate-based solid polymer electrolytes

A series of different composition of polymer electrolytes-based on poly(vinyl chloride) (PVC) as host polymer, lithium tetraborate (Li₂B₄O₇) as dopant salt, and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The interaction between the PVC, Li₂B₄O₇, and DBP were studied by Fourier transform infrared. The shifting, broadening, and splitting of transmission peaks were the evidences of complexation. The highest ionic conductivity polymer electrolyte of 2.83 × 10⁻⁶ S/cm was achieved at ambient temperature upon addition of 30 wt.% of DBP. In addition, the temperature-dependent conductivity, frequency-dependent conductivity, dielectric permittivity, and modulus studies were performed. The temperature-dependent conductivity of the polymer electrolytes was found to obey the Arrhenius behavior. The thermal stability of polymer electrolytes was verified by thermogravimetric analysis. The lower in glass transition temperature was proven in differential scanning calorimetry, whereas the higher amorphous region within the polymer matrix was demonstrated in X-ray diffraction.     

Structural and electrochemical characteristics of 49% PMMA grafted polyisoprene-LiCF3SO3-PC based polymer electrolytes

Gel polymer electrolytes consisting of 49% PMMA grafted polyisoprene-LiCF₃SO₃, were plasticized with propylene carbonate (PC) are reported. The effect of PC on the electrochemical properties of the polymer electrolyte has been investigated. Analysis of FTIR spectra shows the interaction of salt and plasticizers with the polymer chain. The ionic conductivity was measured and exhibited a maximum value of 10⁻⁴ S/cm. The temperature dependence of the electrical conductivity follows the Arrhenius law. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Conductivity, dielectric behaviour and thermal stability studies of lithium ion dissociation in poly(methyl methacrylate)-based gel polymer electrolytes

Thin films of poly(methyl methacrylate) (PMMA) with lithium triflate (LiCF₃SO₃) were prepared by using the solution-casting method with PMMA as the host polymer. Ionic conductivity and dielectric measurements were carried out on these films. The highest conductivity for polymer electrolyte with a ratio of 65:35 was found to be 9.88 × 10⁻⁵ S cm⁻¹, which is suitable for the production of mobile phone battery. Thermal gravimetric analysis was carried out to evaluate the thermal stability of the polymer electrolyte. The addition of salts will increase thermal stability of the polymer electrolyte.     

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.     

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.