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1.
A comb-shaped polymer was prepared from a vinyl ether monomer comprising three oxyethylene units with a terminal methoxy group. The polymer could dissolve LiClO4, NaClO4, and LiSO3CF3 salts to form homogeneous amorphous mixtures, and the glass transition temperatures in each system were observed to increase with added salt. A.c. conductivity studies on the mixtures of polymer-LiClO4 showed a dependence on both salt concentration and temperature. Room temperature conductivities were around 10?5Scm?1 rising to about 10?3Scm?1 at ~ 380K. A maximum in the conductivity was detected which altered with temperature. Conductivities which displayed non-Arrhenius behaviour were analysed using the Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model derived by Gibbs and coworkers.  相似文献   

2.
A novel ionic liquid of trifluoroacetic propylamine, i.e., [CH3CH2CH2NH3+] [CF3COO] (TFAPA), was synthesized from trifluoroacetic acid and propylamine. The ionic liquid of TFAPA was used to prepare anhydrous, conducting membranes based on polymers of sulfonated poly (ether ether) ketone (SPEEK) or polyvinylidenefluoride (PVDF). The ionic conductivity and mechanical strength of the composite membranes were investigated at elevated temperatures and under anhydrous conditions. Conductivity of 0.030 S/cm was achieved with TFAPA at 180 °C, and of 0.019 S/cm with a membrane containing 70% (wt) TFAPA in SPEEK with a sulfonation degree of 86% at 160 °C. Increasing either ionic liquid content or temperature reduced the mechanical strength of the composite membrane. Efforts were made to improve the strength of TFAPA/SPEEK composite membranes by cross-linking the SPEEK, which led to some strength enhancement at 110 °C and 130 °C.  相似文献   

3.
Poly(ether urethanes) obtained by the copolymerization of poly(ethylene glycol) (PEG) and lysine ethyl ester (LysOEt) are elastomeric materials that can be processed readily to form flexible, soft films. In view of these desirable physicomechanical properties, the potential use of these new materials as solid polymer electrolytes was explored. Solid polymer electrolytes were prepared with copolymers containing PEG blocks of different lengths and with different concentrations of lithium triflate (LiCF3SO3). Correlations between the length of the PEG block, the concentration of lithium triflate in the formulation, and the observed Li+ ion conductivity were investigated. Solid electrolyte formulations were characterized by differential scanning calorimetry for glass transition temperatures (Tg), melting points (Tm), and crystallinity. Ionic conductivity measurements were carried out on thin films of the polymer electrolytes that had been cast on a microelectrode assembly using conventional ac-impedance spectroscopy. These polymer electrolytes showed inherently high ionic conductivity at room temperature. The optimum concentration of lithium triflate was about 25–30% (w/w), resulting at room temperature in an ionic conductivity of about 10−5 S cm−1. For poly(PEG2000-LysOEt) containing 30% of LiCF3SO3, the activation energy was ∼ 1.1 eV. Our results indicate that block copolymers of PEG and lysine ethyl ester are promising candidates for the development of polymeric, solvent-free electrolytes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1449–1456, 1997  相似文献   

4.
Two oxetane‐derived monomers 3‐(2‐cyanoethoxy)methyl‐ and 3‐(methoxy(triethylenoxy)) methyl‐3′‐methyloxetane were prepared from the reaction of 3‐methyl‐3′‐hydroxymethyloxetane with acrylonitrile and triethylene glycol monomethyl ether, respectively. Their homo‐ and copolyethers were synthesized with BF3· Et2O/1,4‐butanediol and trifluoromethane sulfonic acid as initiator through cationic ring‐opening polymerization. The structure of the polymers was characterized by FTIR and1H NMR. The ratio of two repeating units incorporated into the copolymers is well consistent with the feed ratio. Regarding glass transition temperature (Tg), the DSC data imply that the resulting copolymers have a lower Tg than pure poly(ethylene oxide). Moreover, the TGA measurements reveal that they possess in general a high heat decomposition temperature. The ion conductivity of a sample (P‐AN 20) is 1.07 × 10?5 S cm?1 at room temperature and 2.79 × 10?4 S cm?1 at 80 °C, thus presenting the potential to meet the practical requirement of lithium ion batteries for polymer electrolytes. Copyright © 2005 Society of Chemical Industry  相似文献   

5.
Poly(phthalazinone ether ketone) (PPEK) is an amorphous thermoplastic polymer with a high glass transition temperature (Tg) exceeding 250°C. We describe the preparation of foams from PPEK and characterize their properties. PPEK foams were prepared using dichloromethane as a foaming agent. The foaming agent was swollen into discs of the PPEK, which were then foamed by heating. Foams could be prepared at temperatures far below the Tg of the PPEK due to plasticization of the polymer by the foaming agent. Foams with densities ranging from 0.1 to 0.65 g/cm3 were prepared. Their thermal conductivity and modulus (measured approximately by indentation tests) were found to decrease with density, and the trends were similar to those expected from existing models. The foams could be annealed at 200°C without collapse suggesting that they may be useful in structural or insulation applications where stability at high temperature is essential.  相似文献   

6.
Summary Three comb polymers(CP) with oligo-oxyethylene side chains of the type-O(CH2CH2O)nCH3 were prepared from methyl vinyl ether/maleic anhydride alternating copolymer. Homogeneous amorphous polymer electrolytes were made from CP and LiCF3SO3 or LiClO4 by solvent-casting method, and their conductivities were measured as a function of temperature and salt concentration. The conductivity which displayed non-Arrhenius behaviour was analyzed using the Vogel-Tammann-Fulcher equation. The conductivity maximum appears at lower salt concentration when CP has longer side chains. XPS was used to study the cation-polymer interaction.  相似文献   

7.
The development of morphological solid-state structures in sulfonated poly(arylene ether sulfone) copolymers (acid form) by hydrothermal treatment was investigated by water uptake, dynamic mechanical analysis (DMA), and tapping mode atomic force microscopy (TM-AFM). The water uptake and DMA studies suggested that the materials have three irreversible morphological regimes, whose intervals are controlled by copolymer composition and hydrothermal treatment temperature. Ambient temperature treatment of the membranes afforded a structure denoted as Regime1. When the copolymer membranes were exposed to a higher temperature, AFM revealed a morphology (Regime2) where the phase contrast and domain connectivity of the hydrophilic phase of the copolymers were greatly increased. A yet higher treatment temperature was defined which yielded a third regime, likely related to viscoelastic relaxations associated with the hydrated glass transition temperature (hydrated Tg). The required temperatures needed to produce transitions from Regime1 to Regime2 or Regime3 decreased with increasing degree of disulfonation. These temperatures correspond to the percolation and hydrogel temperatures, respectively. Poly(arylene ether sulfone) copolymer membranes with a 40% disulfonation in Regime2 under fully hydrated conditions showed similar proton conductivity (∼0.1 S/cm) to the well-known perfluorinated copolymer Nafion® 1135 but exhibited higher modulus and water uptake. The proton conductivity and storage modulus are discussed in terms of each of the morphological regimes and compared with Nafion 1135. The results are of particular interest for either hydrogen or direct methanol fuel cells where conductivity and membrane permeability are critical issues.  相似文献   

8.
The unsaturated polyoxyethylene (PEO) was synthesized by copolymerization of ethylene oxide with allyl glycidyl ether in toluene using bimetallic-oxo-alkoxide as a catalyst. The effects of polymerization conditions on conversion and intrinsic viscosity of the copolymer were studied. The unsaturated copolymer was characterized with infrared spectra, 1H NMR, and wide-angle X-ray diffraction. The relationship between crystallinity of the copolymers and conductivity of their LiClO4 complexes were investigated. The copolymer with ∼ 65 wt % PEO content exhibits a room temperature conductivity of 1 × 10−4 S cm−1 at a molar ratio of EO/Li = 20. The unsaturated PEO was graft-copolymerized with styrene using 2,2′-azobis(isobutyronitrile) as initiator in toluene, with grafting efficiency ∼ 50%. The purified graft copolymer was characterized with infrared spectra, 1H NMR, and wide-angle X-ray diffraction, and was shown to have good emulsifying properties and a phase-transfer catalytic property. LiClO4 complex of the graft copolymer with 70 wt % PEO content exhibits a room temperature conductivity approaching 1 × 10−4 S cm−1 at molar ratio of EO/Li = 20/1. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2417–2425, 1998  相似文献   

9.
P-octyl polyethylene glycol phenyl ether (Triton X-100) and cetyltrimethylammonium bromide (CTAB) were mixed to be used as surfactant for preparing reverse microemulsion with n-hexane, n-hexanol and water. Effects of weight ratio of the two surfactants, temperature, concentrations of water and cosurfactant on the conductivity were studied. The results indicate that the conductivity of the mixed surfactants reverse microemulsion is greatly higher than that of the single surfactant system. The reverse microemulsion has been modified to be with good conductivity. The weight ratio of the two surfactants, temperature, concentrations of water and cosurfactant have obvious effects on the conductivity of the reverse microemulsion. Furthermore, the electrochemical behavior of potassium ferricyanide [K3Fe(CN)6] in the mixed surfactants reverse microemulsion was investigated by cyclic voltammetry. The result shows that the redox processes of \textFe( \textCN ) 6 3- / \textFe( \textCN ) 6 4- {{\text{Fe}}\left( {\text{CN}} \right)_{ 6}}^{ 3- } / {{\text{Fe}}\left( {\text{CN}} \right)_{ 6}}^{ 4-} present good reversibility and are controlled by diffusion in the system.  相似文献   

10.
A crosslinked polyether network was prepared from poly(ethylene glycol) diglycidyl ether (PEGDE) cured with poly(propylene oxide) polyamine. Significant interactions between ions and polymer host have been observed for the crosslinked polyether network in the presence of LiClO4 by means of FT-IR, DSC, TGA, and 7Li MAS solid-state NMR. Thermal stability and ionic conductivity of these complexes were also investigated by TGA and AC impedance measurements. The results of FT-IR, DSC, TGA and 7Li MAS solid-state NMR measurements indicate the formation of different types of complexes through the interaction of ions with different coordination sites of polymer electrolyte networks. The dependence of ionic conductivity was investigated as a function of temperature, LiClO4 concentration and the molecular weight of polyether curing agents. It is observed that the behavior of ion transport follows the empirical Vogel-Tamman-Fulcher (VTF) type relationship for all the samples, implying the diffusion of charge carrier is assisted by the segmental motions of polymer chains. Moreover, the conductivity is also correlated with the interactions between ions and polymer host, and the maximum ionic conductivity occurs at the LiClO4 concentration of [O]/[Li+]=15.  相似文献   

11.
The proton exchange membrane (PEM) is the core component of a high-performance proton exchange membrane fuel cell (PEMFC). Since the traditional PEM has the disadvantages of poor cell performance and high cost, a new kind of PEM with good proton conductivity, low cost and simple preparation should be explored. In this paper, several different binary hybrid membranes were successfully prepared through one-step encapsulation of different ionic liquids (ILs) in sulfonated poly(ether ether ketone) (SPEEK). The prepared membranes were characterized by scanning electron microscope (SEM), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), proton conductivity measurements and dynamic mechanical analysis (DMA). SEM images showed that ILs were fully doped into SPEEK. FT-IR and XPS proved that SPEEK and IL formed a new chemical bond combined with intermolecular hydrogen bonds. The TG results showed that the binary hybrid membranes could maintain stability even at 300°C. The water uptake and swelling ratio showed that the water absorption capacity of the binary composite membrane played a vital role in improving proton conductivity. The proton conductivity study showed that ILs doping also helped to improve the proton conductivity of the SPEEK membrane. When the doping amount of IL was maintained at 30 wt.%, it has the highest proton conductivity, 25 mS cm−1 at 120°C. It was proved that anhydrous hybrid membrane tetraphenyl imidazole sulfate/SPEEK ([IM2][H2PO4]/SPEEK) could be used in PEMFC at medium temperature.  相似文献   

12.
A poly(styrenesulfonate) lithium salt was tested as a single-ion conductor in a poly(ethylene oxide)/poly(ethylene glycol) dimethyl ether matrix. Impedance spectroscopy and voltage step polarization were used to characterize the composite electrolytes. A specific conductivity of about 7×10−8 S cm−1 was evaluated at 70 °C. The very low conductivity was attributed to the poor solubility of Li+ in the polymer matrix. AlCl3 was added to the polymer electrolyte to increase the salt dissolution. The addition of the Lewis acid strongly increases the conductivity and a specific conductivity of about 4×10−6 S cm−1 was measured at 20 °C. For temperature lower than 60 °C, the specific conductivity dependence with increasing temperature follows an Arrhenius-type behavior. An activation energy of about 55.6 kJ mol−1 was calculated. A very similar activation energy (60.3 kJ mol−1) was found for the charge transfer resistance. The transport properties of the polymer electrolyte were tested by applying a d.c. voltage step to a symmetrical lithium cell. The current at the applied voltage decreased with time. The decrease was related to an increase in the cell resistance due to the continuous growth of a passivation layer on the lithium surface.  相似文献   

13.
The mixed conductivity (ionic and electronic) of Ag2S was measured at room temperature by a square wave method. Various types of cells were used. They allowed blocking of either the ionic or electronic current in the steady state. The electronic conductivity was very different depending upon whether the Ag2S was contacted with metallic silver or not, the ratio of electronic to ionic conductivity being 3·22 or 0·015, respectively. The ionic conductivity was the same in both cases, in agreement with theoretical expectations for a system with high ionic disorder and relatively small electronic disorder. The measurements yielded also information about the kinetics of the exchange of Ag+ -ions at the interface Ag2S Agaq. It was estimated that the exchange current density is at least 100 mA cm2 for a 0·1 M AgNO3 solution. In contrast to this the kinetics of a redox process (Fe3?aq + e → Fe2+aq) were found to be very slow. These two features are favourable from the viewpoint of the use of Ag2S as an ion selective electrode.The kinetics of the Ag/Ag+aq interface were also studied. Especially with AgNO3 solutions the polarisation resistance is extremely high near the equilibrium potential (at cd's of the order of μA/cm2) and drops suddenly at potentials above about 5–10 mV. The phenomena observed are probably due to adsorption effects. The difference between the behaviour of the Ag and Ag2S interfaces is discussed.  相似文献   

14.
The direct and alternating current conductivity, space charge limited current, and thermoelectrical properties of boron‐containing poly(vinyl alcohol)‐derived ceramic have been investigated. The electrical conductivity of the sample increases with increase in temperature and the room temperature conductivity of the sample was found to be 3.82 × 10?5 S/cm. The electrical conductivity and thermoelectric power results suggest that the PVAB polymer has p‐type electrical conductivity. The current–voltage characteristics indicate that at higher voltages, the space charge limited conductivity mechanism is dominant in the PVAB sample. The electronic parameters such as the position of the Fermi level bottom of the conduction band, EF, the density of states in conduction band Nc, effective mass of holes ms were found to be 0.44 eV, 2.12 × 1025 m?3, and 0.59 mo, respectively. Alternating current conductivity results suggest that the correlated barrier hopping conductivity is dominant in AC conductivity mechanism of the sample. The imaginary part of the dielectrical modulus at different temperatures shows a relaxation peak, indicating a temperature‐dependent non‐Debye relaxation. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers  相似文献   

15.
The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF3SO3, LiBr and LiClO4 were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and 13C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li+ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion-cation association consistent with increasing LiCF3SO3 concentrations. Moreover, the 13C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. Tg and Td of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li+ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.  相似文献   

16.
Most of the anhydrous proton conducting membranes are based on inorganic or partially inorganic materials, like SrCeO3 membranes or polybenzimidazole (PBI)/H3PO4 composite membranes. In present work, a new kind of anhydrous proton conducting membrane based on fully organic components of PBI and tridecyl phosphate (TP) was prepared. The interaction between PBI and TP is discussed. The temperature dependence of the proton conductivity of the composite membranes can be modeled by an Arrhenius relation. Thermogravimetric analysis (TGA) illustrates that these composite membranes are chemically stable up to 145 °C. The weight loss appearing at 145 °C is attributed to the selfcondensation of phosphate, which results in the proton conductivity drop of the membranes occurring at the same temperature. The DC conductivity of the composite membranes can reach ∼10−4 S/cm for PBI/1.8TP at 140 °C and increases with increasing TP content. The proton conductivity of PBI/TP and PBI/H3PO4 composite membranes is compared. The former have higher proton conductivity, however, the proton conductivity of the PBI/H3PO4 membranes increases with temperature more significantly. Compared with PBI/H3PO4 membranes, the migration stability of TP in PBI/TP membranes is improved significantly.  相似文献   

17.
A novel series of hydrocarbon‐based copolymers containing flexible alkylsulfonated groups and hydroxylated poly(ether ether ketone) backbones was designed and prepared as proton conducting membranes. Among the membranes, the membrane SPO3–(PMS–PSBOS)2 with the ion exchange capacity 1.70 showed good proton conductivity at 0.137 S/cm at 80 °C, which was two times as much as that of the control membrane SPO. Further, incorporating the sulfonated graphene oxide (s‐GO) into SPO3–(PMS‐PSBOS)2 leads to the composite membrane SPO3–(PMS–PSBOS)2–SGO, which exhibited higher proton conductivity compared to Nation 117 and the native membrane SPO3–(PMS–PSBOS)2. In addition, the composite membrane SPO3–(PMS–PSBOS)2–SGO showed well‐defined phase separated structures and high selectivity (1.40 × 105 Ss/cm3), which were about three times as that of Nafion 117 (0.52 × 105 Ss/cm3). These results suggested that these membranes are promising materials for direct methanol fuel cell (DMFC) applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45205.  相似文献   

18.
《Ceramics International》2017,43(8):6268-6275
The frequency dependent dielectric and AC conductivity properties of different concentrations of Pr3+ doped Sr0.5Ca0.5TiO3 ceramics were investigated for the frequency range 100 Hz to 2 MHz at different temperatures. The morphology of the prepared samples was analyzed by using Field-Emission Scanning Electron Microscope images. The value of dielectric constant and dielectric loss decreases with increase in the frequency of the applied signal in all the samples. Also, the value of dielectric constant and dielectric loss decreased with doping of different concentrations of Pr3+ ions. The conductivity of the samples obeys Jonscher's power-law and shows a decrease with increasing doping concentration of Pr3+ ions. The higher value of real and imaginary part of impedance at lower frequency indicates the space charge polarization of the material and its absence at higher frequencies was confirmed from the low value of impedance at higher frequency region. The Cole- Cole parameters of the samples were calculated and the semi-circle observed indicates a single relaxation process and can be modeled by an equivalent parallel RC circuit. At lower frequency region, the value of dielectric constant and dissipation factor increases with increase in the temperature. Also the value of conductivity increases with temperature at high frequency region, due to the enhanced mobility of charge carriers.  相似文献   

19.
《Ceramics International》2017,43(10):7810-7815
Sodium zirconium silicon phosphorus with the composition of Na3Zr2Si2PO12 (NZSP) was prepared by a facile solid state reaction method. The effects of the calcination temperature and rare earth element substitution on the structure and ionic conductivity of the NZSP material were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and AC impedance measurement. The results show that the microstructure and ionic inductivity of the NZSP was strongly affected by the aliovalent substitution of Zr4+ ions in NZSP with rare earth metal of La3+, Nd3+ and Y3+. At room temperature, the optimum bulk and total ionic conductivity of the pure NZSP solid electrolyte sintered under different conditions were 6.77×10−4 and 4.56×10−4 S cm−1, respectively. Substitution of La3+, Nd3+ and Y3+ in place of Zr4+ exhibited higher bulk conductivity compared with that of pure NZSP. Maximum bulk and ionic conductivity value of 1.43×10−3 and 1.10×10−3 S cm−1 at room temperature were obtained by Na3+xZr1.9La0.1Si2PO12 sample. The charge imbalance created by aliovalent substitution improves the mobility of Na+ ions in the lattice, which leads to increase in the conductivity. AC impedance results indicated that the total ionic conductivity strongly depends on the substitution element and the feature of the grain boundary.  相似文献   

20.
The role of cyclophosphazenes with oxyethylene chains (N3P3(OCH2CH2)nOCH3, (n = 3, 3, n = 7.2, 4) and N4P4[OC6H4O(CH2CH2O)7.2CH3]8 (8) for the synthesis and ionic conductivity in polymethacrylate networks was studied. Reflecting the structural features of cyclophosphazenes, the 7Li NMR spectra of the mixture of 3 and LiN(SO2CF3)2 showed that more than 40% of the Li+ salt could exist as a free ion at room temperature. Similar values were obtained for 4 and 8. Cross-linked methacrylate polymers (1214, and 1618) were prepared from the reaction of poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate both in the presence of these cyclophosphazenes which act as molecular imprinting molecules (method II, M-II) and without the cyclophosphazene (method I) DSC studies of the imprinted polymer, 12(20)/3/Li+ system after removal of the cyclophosphazene showed that the glass transition temperature range (ΔTg) becomes significantly narrower compared to that of the unimprinted 11(20)/3/Li+ system, where cross-linked polymer 11(20) was prepared in the absence of the cyclophosphazenes (method I, M-I). The ionic conductivity of the Li+/cross-linked polymer system was improved by the subsequent readdition of the cyclophosphazenes. The 12(20)/3/Li+ complex showed a conductivity of 1.1 × 10−3 S/cm at 90 °C, which was two times higher than that of the 11(20)/3/Li+ complex. The effectiveness of the small molecule imprinting technique for the preparation of cross-linked polyelectrolytes with high conductivity and mechanical stability is discussed. We dedicate this paper to Professor Christopher W. Allen for his creative, pioneering work in inorganic ring and inorganic-organic hybrid polymers.  相似文献   

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