Effect of ZnO nanoparticles on the structure and ionic relaxation of poly(ethylene oxide)-LiI polymer electrolyte nanocomposites

The effect of ZnO nanoparticles on the structure and ionic relaxation of LiI salt doped poly(ethylene oxide) (PEO) polymer electrolytes has been investigated. X-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy show that ZnO nanoparticles dispersed in the PEO-LiI polymer electrolyte reduce the crystallinity of PEO and increase relative smoothness of the surface morphology of the nanocomposite electrolyte. The electrical conductivity of the nanocomposites is found to increase due to incorporation of ZnO nanoparticles. We have shown that the structural modification due to insertion of ZnO nanoparticles results in the enhancement of the mobility i.e., the hopping rate of mobile Li+ ions and hence the ionic conductivity of PEO-LiI-ZnO nanocomposite electrolyte.     

Enhancement of the ionic conductivity of poly(ethylene oxide) electrolyte film by polyaniline addition

To improve the electrical conductivity of LiClO₄–poly(ethylene oxide) (PEO) complex, nonconductive polyaniline (NPANI) was employed as an additive. The electrical conductivity of the PEO–LiClO₄–NPANI electrolyte was at least ten times that of the original PEO–LiClO₄ electrolyte. The amine and/or imine nitrogen atoms in the NPANI polymer chain as well as the oxygen atoms in the PEO poly-merchain attracted the Li⁺ ions, and ion-dipole interaction occurred. The interaction enhanced the mobility of the ClO₄ ^– ions. The positively charged nitrogens were electronically stabilized in the entire polymer chain because NPANI had conjugated electrons. The mechanism is unique and different from those of other polymer additives. It is the very first example in which NPANI was employed as the additive for the PEO solid electrolyte and in which NPANI was found to be an effective additive. In addition, the NPANI addition hardly affected the physical properties of the PEO matrix such as the glass transition temperature and the melting temperature.     

Synthesis and characterization of conjugated poly (amino benzyl alcohol) and poly (ethylene glycol) for solid polymer electrolyte

A solid polymer electrolyte chemically bonded to a π-conjugated polymer was prepared for the use as a designed ladder-type structure by the graft copolymerization of poly (aminobenzyl alcohol) (PABA) with poly (ethylene glycol) (PEG). PABA was used as the frame for the ladder and the PEG as the rungs. The expected synergic effect afforded by the introduction of the ionic salts into the crosslinked conjugated polymer and PEG network was investigated as a function of its structure, morphology, and ionic conductivity. The insertion of the ionic salts into the PABA-PEG-PABA network led to the enhancement of the ionic conductivity compared to that of PEG/LiClO₄. The synergic effect may be explained by the more efficient segmental motion of the polymer chains or better ion mobility in the network due to the interrupted crystallization of the PEG chains. The fine tuning of the crosslinked conjugated polymer gel might enable it to show a faster response to electrochemical stimuli.     

Local thermal-mechanical analysis of ultrathin interfacially mixed poly(ethylene oxide)/poly(acrylic acid) layer-by-layer electrolyte assemblies

Ion conductivities of layer-by-layer (LBL) assemblies of solid thin film polyelectrolyte systems involving poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) were found to be a strong function of the number of bilayer stacks, n, with conductivities approaching 10^− 7 S/cm for n < 10, compared to 10^− 9 S/cm for n ≥ 10 and 10^− 10 S/cm for bulk PEO. Increased ion conductivity for low LBL stack numbers (n < 10) originated to part from an effective suppression of the PEO crystallization via PEO/PAA blending, which could be inferred from local glass transition temperature measurements involving shear modulation force microscopy. Another phenomenon responsible for high conductivity in thin films was found in the in-plane phase heterogeneity of PEO and PAA. Increased ion conductivity for larger LBL stacks (n ≥ 10) were attributed to low concentration autoblending caused by PEO-PAA hydrogen bonding, and an average layer thickness of noticeably less than 100 nm. The effect of interfacial constraints was evident in the degree of intermixing, addressed by a thin film extended Fox blend analysis, in the glass and melting transitions of PEO and PAA pure film components. While the glass transition value of PAA decreased by 55% to 46 °C for an 8 nm film, the melting transition for PEO decreased by 15% to 64 °C caused by surface tension effects.     

Influence of tetrapod-shaped zinc oxide whisker on poly(vinylidene fluoride) based gel polymer electrolyte

The influence of zinc oxide whisker (ZnO_w) on the ionic conductivity of poly(vinylidene fluoride) (PVdF) based gel polymer composite electrolyte was investigated by impedance spectroscopy. The critical volume content (V_c) to constitute the ideal network channel was calculated theoretically, and it was found that V_c was higher than that of the experimental result.     

Study of poly (methyl methacrylate)/poly (ethylene oxide) blends in solution. II

In this paper, the equilibrium properties for the poly (methyl methacrylate)/poly (ethylene oxide) system have been studied in 1, 2,dichloroethane and methyl acetate separately. Viscometry and laser light scattering techniques have been employed. The results obtained from both methods can be compared. From this comparison it turns out that the compatibility decreases as the PEO molecular weight increases at constant molecular weight of PMMA. On the contrary, the compatibility increases as the PMMA molecular weight increases for the same PEO molecular weight.     

An acrylate-based quasi-solid polymer electrolyte incorporating a novel dinitrile poly(ethylene glycol) plasticizer for lithium-ion batteries

Journal of Materials Science - The performance of solid polymer electrolytes is characterized by lower ionic conductivity than conventional liquid electrolytes but provides advantages in terms of...     

Selective binding of NH4 + by redox-active crown ethers: application to a NH4 + sensor

Two redox-active crown ethers, (1,1'- bi-2-naphthyl)-23-crown-6 incorporating 9,10-anthraquinone (BNAQ) and 1,4-benzoquinone (BNBQ), were synthesized and employed in the selective binding of NH(4)(+) over K(+). Their applications to NH(4)(+) detection were studied by cyclic voltammetry and amperometry in aqueous media. The results showed that the magnitude of the quinone redox peak decreased linearly as the concentration of NH(4)(+) increased, indicating the formation of BNAQ-NH(4)(+) and BNBQ-NH(4)(+) complexes. Formation constants of BNAQ-NH(4)(+) and BNBQ-NH(4)(+) complexes were determined to be 4.3 x 10(3) and 4.0 x 10(3) M(-1), respectively, which were 2 orders of the magnitude greater than those of BNAQ-K(+) and BNBQ-K(+) complexes. The (1)H NMR titration method carried out in DMSO-d(6) showed that both complexes possessed 1:1 stoichiometry, and association constants were determined to be 648 +/- 35 and 600 +/- 47 M(-1) for BNAQ-NH(4)(+) and BNBQ-NH(4)(+), respectively. Interference effects from other alkali and alkaline earth metal ions in the analysis of NH(4)(+) were also investigated. The BNAQ-modified sensor showed a linear response from 1.0 microM to 1.0 mM for NH(4)(+), and the detection limit was determined to be 0.9 +/- 0.03 microM.     

3-Methyltrimethylammonium poly(2,6-dimethyl-1,4-phenylene oxide) based anion exchange membrane for alkaline polymer electrolyte fuel cells

Hydroxyl ion (OH^?) conducting anion exchange membranes based on modified poly (phenylene oxide) are fabricated for their application in alkaline polymer electrolyte fuel cells (APEFCs). In the present study, chloromethylation of poly(phenylene oxide) (PPO) is performed by aryl substitution rather than benzyl substitution and homogeneously quaternized to form an anion exchange membrane (AEM). ¹H NMR and FT-IR studies reveal successful incorporation of the above groups in the polymer backbone. The membrane is characterized for its ion exchange capacity and water uptake. The membrane formed by these processes show good ionic conductivity and when used in fuel cell exhibited an enhanced performance in comparison with the state-of-the-art commercial AHA membrane. A peak power density of 111 mW/cm² at a load current density of 250 mA/cm² is obtained for PPO based membrane in APEFCs at 30 °C.     

Linear poly(ethylene oxide)-based polyurethane hydrogels: polyurethane-ureas and polyurethane-amides

Over the last 30 years, water-swellable and water-insoluble hydrogels have been extensively investigated and developed, leading to a large family of materials which have found uses in a wide range of biomedical applications. While hydrogels usually present a crosslinked structure, linear polyurethane-ureas (PUUs) based on poly(ethylene oxide) have been shown to be able to absorb and swell with aqueous media without dissolving. This behavior is due to the phase separated domain morphology, where hydrogen bonded urethane/urea hard segment domains are dispersed in a PEO soft segment domain. This work investigates the possibility of obtaining linear poly(ethylene oxide)-based polyurethane-amide (PUA) hydrogels using two amide diols as chain extenders, a mono amide diol (AD) and a diamide diol (DD), and a dicarboxylic acid (maleic acid, MA). Poly(ethylene oxide) based PUAs were obtained using a “one-shot” bulk polymerization technique. The chemicophysical characterization and water-solubility tests showed that these materials, while having molecular weights similar to the PUUs, do not possess sufficient phase separation, hydrogen bonding and hydrophobicity of the hard segment domains to exhibit hydrogel behavior. Crosslinked PUAs using maleic acid as chain extender show interesting hydrogel properties. © 1999 Kluwer Academic Publishers     

Some new aspects of the phase diagram of the NH 4 + /H+-W-O system

The phase composition of partially-reduced products of ammonium paratungstate (APT) was investigated. The samples were prepared by reducing the APT in a H₂ + N₂/129 volume ratio/atomosphere in the temperature range 610 to 860 K, and studied by means of chemical analysis, by X-ray diffraction analysis and by thermoanalytical methods. The reduction products can be described by the general formula of M _xWO_3–y+x/2 where M can be either H⁺ and/or NH ₄ ⁺ . Products considered as tungsten bronzes (TB) can be formed in a fairly narrow temperature range. Another product, the so-called decomposed APT (DAPT) is a mixture of bronzes and of some other compounds characterized by y/2 and considered as some intermediate phases between TB and tungstates.     

Study of effect of composition, irradiation and quenching on ionic conductivity in (PEG) x : NH4NO3 solid polymer electrolyte

We have prepared, characterized and investigated a new PEG-2000 based solid polymer electrolyte (PEG) _x : NH₄NO₃. Ionic conductivity measurements have been made as a function of salt concentration as well as temperature in the range 265–330 K. Selected compositions of the electrolyte are exposed to a beam of 8 MeV electrons and ⁶⁰Co γ-rays to an accumulated dose of 10 kGy to study the effect on ionic conductivity. The electrolyte samples are also quenched at liquid nitrogen temperature and conductivity measurements are carried out. The ionic conductivity at room temperature exhibits a characteristic peak for the composition, x = 46. Electron beam irradiation results in an increase in conductivity for all compositions by a factor of 2–3. Exposure to γ-rays enhances the conductivity by one order of magnitude. Quenching at low temperature has resulted in an increase in conductivity by 1–2 orders of magnitude. The enhancement of conductivity upon irradiation and quenching is interpreted as due to an increase in amorphous region and decrease in crystallinity of the electrolyte. DSC and NMR measurements also support this conclusion.     

Impact of ethylene carbonate on ion transport characteristics of PVdF-AgCF3SO3 polymer electrolyte system

The ionic transport in thin film plasticized polymer electrolytes based on polyvinylidene fluoride (PVdF) as the polymer host, silver triflate (AgCF₃SO₃) as salt and ethylene carbonate (EC) as plasticizer prepared by solution casting technique has been reported. Addition of silver triflate has resulted in an increase in the room temperature (298 K) electrical conductivity of the polymer from 10⁻⁶ to 10⁻⁵ S cm⁻¹ whereas incorporation of EC as the plasticizer has further enhanced the conductivity value by an order of magnitude to 10⁻⁴ S cm⁻¹ owing to the possible decrease in crystallinity of the polymer matrix as revealed by the detailed temperature-dependent complex impedance, silver ionic transference number, Fourier transform infrared and X-ray diffraction measurements.