Electrochemical sensing for the detection of 2,4-dichlorophenoxy acetic acid using molecularly imprinted polymer membrane

Molecularly imprinted polymer (MIP) membranes were used to develop highly sensitive chemical sensors for the detection of herbicide 2,4-dichlorophenoxy acetic acid (2,4-d). The 2,4-d imprinted composite MIP membranes were prepared, and the characterization was done by UV-VIS spectrophotometer, Fourier transform infrared spectroscopy, and scanning electron microscopy, and the same were fitted in a new electrochemical sensor model. Membrane electroconductivity measurements were performed by applying a small-amplitude alternating voltage (20 mV) with a varying frequency from 20 Hz to 80 kHz generated by a low-frequency wave form generator. The measured changes in the membrane ionic/electric conductivity as a function of 2,4-d concentration was allowed to evaluate the recognition properties of the prepared membrane. This sensor is useful in detecting 2,4-d herbicide having concentration range 10^-3 M to 10^-6 M. The cross-selectivity of the sensor, reproducibility of results, and reusability of MIP membrane were examined and found remarkable and recommendable.     

Electrical and photoelectrical studies of plasma polymerized acrylonitrile

The electrical and photoelectrical properties of plasma polymerized acrylonitrile (PAN) are reported. The polymer films were studied in silver-PAN-silver systems. Electrical conductivity at room temperature was of the order of 10⁻¹¹ ohm⁻¹ cm⁻¹. The space charge limited current (SCLC) studies at room temperature and thermally stimulated current studies (TSC) over a temperature range of 290–500°K led to a clear understanding of carrier concentration, carrier mobility, trapping levels and activation energies. Photoelectric measurements were used to draw a band picture in plasma depositedPAN.     

Structural,thermal and electrical properties of polyvinyl alcohol/poly(vinyl pyrrolidone)–sodium nitrate solid polymer blend electrolyte

Sodium ion conducting solid polymer blend electrolyte thin films have been prepared by using polyvinyl alcohol (PVA)/poly(vinyl pyrrolidone) (PVP) with NaNO₃ by solution cast technique. The prepared films were characterized by various methods. The complexation of the salt with the polymer blend was identified by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR), Differential scanning calorimetry was used to analyze the thermal behavior of the samples, and the glass transition temperature is low for the highest conducting polymer material. The scanning electron microscopy gives the surface morphology of the polymer electrolytes. The frequency and temperature dependent of electrical conductivities of the films were studied using impedance analyzer in the frequency range of 1 Hz to 1 MHz. The highest electrical conductivity of 50PVA/50PVP/2 wt% NaNO₃ concentration has been found to be 1.25 × 10^?5 S cm^?1 at room temperature. The electrical permittivity of the polymer films have been studied for various temperatures. The transference number measurements showed that the charge transport is mainly due to ions than electrons. Using this highest conducting polymer electrolyte, an electrochemical cell is fabricated and the parameters of the cells are tabulated.     

Synthesis and ionic conductivity of polymeric ion gel containing room temperature ionic liquid and phosphotungstic acid

Composite electrolyte comprising phosphotungstic acid (PWA) filler and 1-butyl-3-methyl-imidazolium-tetrafluoroborate (BMImBF₄) room temperature ionic liquid (RTIL) in poly(2-hydroxyethyl methacrylate) (PHEMA) matrix has been prepared. The polymer matrix was formed by free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) monomers. BMImBF₄ was used as both ionic source and plasticizer, and PWA filler provided the proton conductivity in this system. The interactions and structure changes of the PHEMA-RTIL-PWA composites were investigated by Fourier transform infrared spectra, differential scanning calorimetry, and X-ray diffraction. PWA fillers maintained their Keggin structure within a limited range and enhanced the ionic conductivity of the composite electrolyte. The electrolyte with PWA at the 2 wt.% showed the highest ionic conductivity of 8 × 10^− 4 S cm^− 1 at room temperature and 96% relative humidity.     

Development of proton conducting biopolymer membrane based on agar–agar for fuel cell

A proton-conducting polymer electrolyte based on agar and ammonium nitrate (NH₄NO₃) has been prepared through solution casting technique. The prepared polymer electrolytes were characterized by impedance spectroscopy, X-ray diffraction, and Fourier transform infra-red spectroscopy. Impedance analysis shows that sample with 60 wt.% NH₄NO₃ has the highest ionic conductivity of 6.57 × 10⁻⁴ S cm⁻¹ at room temperature. As a function of temperature, the ionic conductivity exhibits an Arrhenius behaviour increasing from 6.57 × 10⁻⁴ S cm⁻¹ at room temperature to 1.09 × 10⁻³ S cm⁻¹ at 70 °C. Transport parameters of the samples were calculated using Wagner’s polarization method and thus shows that the increase in conductivity is due to the increase in the number of mobile ions. Fuel cell has been constructed with the highest proton conductivity polymer 40agar/60NH₄NO₃ and the open circuit voltage is found to be 558 mV.

     

Structure, thermal and transport properties of PVAc-LiClO4 solid polymer electrolytes

The lithium ion conducting solid polymer electrolytes (SPE) based on PVAc-LiClO₄ of various compositions were prepared by solution casting technique. Structure and surface morphology characterization were studied by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) measurements, respectively. Thermal and conductivity behavior of polymer-salt complexes were studied by employing differential scanning calorimetry (DSC) and ac impedance measurements, respectively. XRD and SEM analyses indicate the amorphous nature of the polymer-salt complexes. DSC measurements show decrease in T_g with the increase in LiClO₄ concentrations. The bulk conductivity of the PVAc:LiClO₄ polymer electrolytes was found to vary between 7.6×10⁻⁷ and 6.2×10⁻⁵ S cm⁻¹ at 303 K with the increase in salt concentration. The temperature dependence of the polymer electrolyte complexes appear to obey Arrhenius law.     

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.     

Graft polymerization of poly(epichlorohydrin-g-poly((oxyethylene) methacrylate)) using ATRP and its polymer electrolyte with KI

This contribution demonstrates a synthesis of comb polymer consisting of a poly(epichlorohydrin) (PECH) backbone and poly(oxyethylene methacrylate) side chains. Atom transfer radical polymerization (ATRP) was used to directly initiate the chlorine atoms of PECH macroinitiator. The structure of comb polymer was characterized by nuclear magnetic resonance (¹H nuclear magnetic resonance) and Fourier transform infrared (FT-IR) spectroscopy, presenting the successful “grafting from” method using ATRP. The comb polymer was used as a polymer matrix for dissolving potassium iodide (KI) to prepare solid polymer electrolyte. FT-IR spectroscopy indicates that the potassium salts are dissolved in the polymeric matrix due to coordination interaction with the ether oxygens of graft copolymer. Differential scanning calorimetry showed that glass transition temperature (T _g) of polymer electrolytes continuously increased with increasing salt concentration up to 15 wt.%, mostly due to coordinative interactions between the potassium ions and the ether oxygens of polymer matrix. Ionic conductivity at room temperature increased with increasing salt concentrations up to 5 wt.% (maximum ionic conductivity ~3.7 × 10⁻⁵ S/cm), after which it gradually decreased.     

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.     

Ionic conductivity of LiX-oligo(ethylene oxide)-perfluoro polymer ternary hybrids

Polymeric solid electrolytes were prepared from inorganic lithium salts, endo-acetylated oligo(ethylene oxide) and polyanions with perfluoro(ethylene) main chain. High ionic conductivity was found when these ternary hybrids took micro-segregated structures with continuous cylindrical conduction columns of lithium salt-oligo(ethylene oxide) in the sea of perfluoro-poly(electrolytes). The ionic conductivity of more than 10^?5 S/cm was established at room temperature without affecting the processibility and flexibility of resulting hybrid films.     

Effect of ionic liquid on the properties of poly(vinylidene fluoride)-based gel polymer electrolytes

Poly(vinylidene fluoride)-based polymer electrolytes using ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide as the plasticizer were prepared by solution casting method. The effects of the solvent evaporation temperature (SET) and ionic liquid content (ILC) on the properties and structures of the polymer electrolytes were investigated by characterization of scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry, as well as mechanical and ionic conductivity test. It was confirmed that both SET and ILC had significant influence on the morphology, degree of crystallinity, mechanical properties, and ionic conductivity of the prepared polymer electrolytes. With ILC of 40 %, an excellent polymer electrolyte can be obtained at SET of 60 °C, which exhibited ionic conductivity up to ca. 10^?4 S/cm at room temperature, accompanied by excellent tensile strength of 22.8 MPa and elongation at break of 540 %.     

Starch-based gel electrolyte thin films derived from native sago (Metroxylon sagu) starch

Starch-based gel electrolyte (SbGE) thin films were prepared by mixing native sago starch with different amounts of glycerol, and subsequently doped with various types of ionic salts. SbGE thin films showed substantially enhanced mechanical properties and ionic conductivity through incorporating optimal composition of native sago starch, glycerol, and ionic salts. A maximum room temperature ionic conductivity of the order of 10^?3 S cm^?1 was achieved for optimized SbGE thin film consisting of 80 wt% of native sago starch and 20 wt% of glycerol, and doped with 8 wt% of LiCl. SbGE thin films were characterized by Fourier transformed infrared spectrometry, scanning electron microscopy, and electrochemical impedance spectroscopy. Due to their favorable mechanical properties, high ionic conductivity at room temperature, ease of preparation, environmentally benign, and cheap, SbGE thin films show high potential utility as gel electrolyte materials for the fabrication of solid-state electrochemical devices.     

Structural and ionic conductivity studies of solid polymer electrolytes based on poly (vinylchloride) and poly (methylmethacrylate) blends

Thin film of poly (vinylchloride) and poly (methylmethacrylate) blend polymer electrolytes plasticized with a combination of DBP and Li₂SO₄ salts have been prepared by solution casting technique. The prepared films were subjected to a.c. impedance measurements as a function of temperature ranging from 304–373 K. The maximum conductivity at 304 K was found to be 1.24 × 10⁻⁸ S·cm⁻¹ for PVC-PMMA-Li₂SO₄-DBP (7.5-17.5-5-70 mole-%). Temperature dependence studies on the ionic conductivity in the PVC-PMMA-Li₂SO₄-DBP system suggest that the ion conduction follows the Williams-Landel-Ferry (WLF) mechanism, which is further confirmed by Vogel-Tamman-Fulcher (VTF) plots. XRD, FTIR, SEM and thermal studies revealed complex formation in.     

Measurement of ionic conductivity of poly (<Emphasis Type="Italic">N</Emphasis>-vinylimidazole) and its fluoroborate salt in solid state

The conductivity of poly(N-vinylimidazole) (PVIM) and its fluoroborate salt (PVIM–HBF₄) are reported here. N-vinylimidazole is polymerized by free radical method and PVIM–HBF₄ is prepared by acidification of PVIM with HBF₄. The polyelectrolyte so formed has been characterized by infrared, hydrogen-1 nuclear magnetic resonance, thermogravimetric analyzer, and differential scanning calorimetry. Frequency and temperature dependence of AC conductivity has been studied to learn about the electrical conduction behavior in the materials. The electrical conductivity of the new material is found to be in the range of 10⁻⁵ to 10⁻⁶ S cm⁻¹.There is about 10²- to 10³-fold increase in conductivity of the polyelectrolyte. The material is shown to be a predominantly ionic conductor with t _ion ≈ 0.88. Apparent activation energies are found to be 0.397 and 0.250 eV for the polymer and the polyelectrolyte, respectively.     

Effect of ZnO filler concentration on the conductivity, structure and morphology of PVdF-HFP nanocomposite solid polymer electrolyte for lithium battery application

The polyvinylidene difluoride-co-hexafluoropropylene (PVdF-HFP) nanocomposite solid polymer electrolyte films were developed by solution-casting method. PVdF-HFP as a polymer host, lithium perchlorate (LiClO₄) as a salt for lithium ion, and ZnO nanoparticles as fillers were used to form the nanocomposite solid polymer electrolyte films. All the prepared samples were characterized by X-ray diffraction (XRD), differential scanning calorimetry, and scanning electron microscopy. The XRD patterns of the pure and nanocomposite solid polymer electrolyte samples indicate the formation of amorphous phase with 17.5 wt.% of lithium salt and ZnO fillers up to 3 wt.%. The total conductivity and lithium ion transference number were studied at room temperature by using impedance spectroscopy and Wagner’s polarization methods. The highest conductivity at room temperature for solid polymer electrolyte and nanocomposite solid polymer electrolyte are found to be 3.208?×?10^?4 and 1.043?×?10^?3 S/cm, respectively. Similarly, the lithium ion transference number is evaluated for the optimized solid polymer electrolyte and nanocomposite solid polymer electrolyte films with 3 wt.% of ZnO fillers. And it is found that ionic transference number could be enhanced from 92 to 95 % with the addition of nanosized ZnO fillers to the solid polymer electrolyte.     

Conductivity studies of starch-based polymer electrolytes

A proton-conducting polymer electrolyte based on starch and ammonium nitrate (NH₄NO₃) has been prepared through solution casting method. Ionic conductivity for the system was conducted over a wide range of frequency between 50 Hz and 1 MHz and at temperatures between 303 K and 373 K. Impedance analysis shows that sample with 25 wt.% NH₄NO₃ has a smaller bulk resistance (R _b) compared to that of the pure sample. The amount of NH₄NO₃ was found to influence the proton conduction; the highest obtainable room temperature conductivity was 2.83 × 10⁻⁵ S cm⁻¹, while at 100 °C, the conductivity in found to be 2.09 × 10⁻⁴ S cm⁻¹. The dielectric analysis demonstrates a non-Debye behavior. Transport parameters of the samples were calculated using the Rice and Roth model and thus shows that the increase in conductivity is due to the increase in the number of mobile ions.     

Conductivity study of some polymer electrolytes based on polyacrylonitrile

The present paper deals with the room temperature conductivity study of some polymer electrolytes based on polyacrylonitrile, ammonium tetraflouroborate as dopant, and propylene carbonate (PC) and polyethylene glycols (PEG300 and PEG600) as plasticizers. The additions of plasticizers having different dielectric constant have been found to modify the conductivity of polymer electrolytes. The increase in room temperature conductivity with plasticizer addition has been found to depend upon (1) the amount of salt present and (2) amount of plasticizers added. The polymer electrolytes prepared were characterized by X-ray diffraction, scanning electron micrographs, infrared, thermogravimetric, and AC impedance measurements. The highest room temperature conductivity observed in case of these polymer electrolytes was ∼10–13 s/cm.     

Effect of nano γ-Al2O3 addition on ion dynamics in polymer electrolytes

Polymer electrolytes, which hold the key of successful operation of all solid state ionic devices, have been investigated. An amorphous polymer was used to facsimile fast ion transport in the gel polymer electrolytes (GPE) and room temperature conductivity >10⁻³ S/cm can be attained. Further, these electrolytes were transformed into composites by dispersing inorganic particles of γ-Al₂O₃ (11 nm in size) in varying wt.%. An enhancement in the conductivity for an optimum concentration using LiClO₄ as a salt can be obtained and is described in terms of free charge carrier concentration, while the other family of Lithium salts viz. LiTf, LiIm, LiBETI decreases the conductivity marginally. FTIR spectroscopy supports the observed decrease in terms of more association between fillers and salts. It has been realized that the mechanical integrity of these composites increases manifold, without affecting the conductivity, significantly.     

Proton-conducting polymer electrolyte based on PVA-PAN blend doped with ammonium thiocyanate

Blending of polymers is one of the most useful methods for modulating the conductivity of solid polymer electrolytes. Blend polymer electrolytes have been prepared with polyvinyl alcohol (PVA)-polyacrylonitrile (PAN) blend doped with ammonium thiocyanate with different concentrations by solution casting technique, using dimethyl formamide (DMF) as the solvent. The prepared electrolytes are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), ultraviolet (UV), and ac impedance measurement techniques. The increase in amorphous nature of the blend polymer electrolyte by the addition of salt is confirmed by XRD analysis. The complex formation between the polymers and the salt has been confirmed by FTIR analysis. The thermal behavior has been examined using DSC and TGA. The maximum conductivity has been found to be 2.4?×?10^?3 S cm^?1 for 92.5PVA/7.5PAN/25 % NH₄SCN sample at room temperature. The temperature dependence of conductivity has been studied with the help of Arrhenius plot, and the activation energies are calculated. The proton conductivity is confirmed by dc polarization measurement technique. ¹H NMR studies reveal the presence of protons in the sample. A proton battery is constructed with the highest conducting sample, and its open circuit voltage is measured to be 1.2 V     

A new hyperbranched star polyether electrolyte with high ionic conductivity

Hyperbranched poly(glycidol) containing hydroxyl groups was firstly synthesized via anionic polymerization and then reacted with 2-bromoisobutyl bromide to form macroinitiator HPG-Br. Finally, a hyperbranched star polymer (HPG-PPEGMA) was successfully prepared by atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether methacrylate using HPG-Br as macroinitiator. The structures and properties of the obtained polymers were characterized by ¹H NMR, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The ionic conductivity of the polymer electrolytes composed of HPG-PPEGMA and lithium bis(trifluoromethanesulfonimide) (LiTFSI) was investigated via electrochemical impedance spectroscopy. The results showed that the room temperature ionic conductivity of the prepared hyperbranched star polymer electrolytes had a higher ionic conductivity. When [EO]/[Li] was 20, the ionic conductivity of the hyperbranched star polymer electrolyte was up to 1?×?10^?4 Scm^?1 at 30 °C. The onset decomposition temperature of the hyperbranched star polyether could reach 374 °C, indicating that the hyperbranched star polymer had a good thermal stability. The XRD results showed that the structure of the hyperbranched star polymer was beneficial to improve the ionic conductivity due to possessing a low degree of crystallinity.