Effects of poly(ethylene glycol) on electrical conductivity of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic acid) film

A series of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic acid) composite thin films with prescribed concentrations of poly(ethylene glycol) were prepared. The PEDOT–PSS pristine film and PEDOT–PSS/PEG films were studied using four-probe method, photoelectron spectroscopy and atomic force microscopy. The electrical conductivity of PEDOT–PSS/PEG hybrid films was found to be enhanced compared to the PEDOT–PSS pristine film, depending on the PEG concentration and molecular weight. XPS analysis and AFM results showed that PEG induces the phase separation between the PEDOT–PSS conducting particles and the excessive PSSNa shell. Simultaneously PEG may form hydrogen bond with sulfonic groups of PSSH, and hence weaken the electrostatic interactions between PEDOT cationic chains and PSS anionic chains. These resulted in the creation of a better conduction pathway among PEDOT–PSS particles, attributed to the improvement of conductivity.     

Conductivity studies of poly(ethylene oxide)(PEO)/poly(vinyl alcohol) (PVA) blend gel polymer electrolytes for dye-sensitized solar cells

Poly(ethylene oxide)(PEO)–poly(vinyl alcohol) (PVA) blend-based gel polymer electrolytes (GPEs) have been prepared by blending equal weights of PEO and PVA in ethylene carbonate (EC), dimethyl sulfoxide (DMSO), tetrabutylammonium iodide (TBAI), and iodine crystals (I₂). The conductivity, diffusion coefficient, number density, and ion mobility of the electrolytes have been calculated from the impedance data obtained from electrochemical impedance spectroscopy (EIS) measurements. The GPE with the composition of 7.02 wt%, PVA, 7.02 wt% PEO, 30.11 wt% ethylene carbonate (EC), 30.11 wt% DMSO, 24.08 wt% TBAI and 1.66 wt% I₂ exhibits the highest conductivity of 5.5 mS cm^?1 at room temperature. Dye-sensitized solar cells (DSSCs) with configuration fluorine tin oxide (FTO)/titanium dioxide/N3-dye/GPE/platinum/FTO have been fabricated and tested under the white light of intensity 100 mW cm^?2. The DSSC containing the highest conducting GPE exhibits the highest power conversion efficiency, η of 5.36 %.     

Star-shaped oligo(ethylene glycol) ethers (OEGE) as a new type of plasticizer for polymer gel electrolytes

Star-shaped oligo(ethylene glycol) methyl ethers (three and four arm molecules of various molecular weights) were synthesized and characterized with regard to viscosity, thermal transitions, ability to solvate the electrolyte LiCF₃SO₃ and the ionic conductivity of their LiCF₃SO₃ solutions in comparison to linear oligo(ethylene glycol) methyl ethers. Polymer gel electrolytes were prepared by photopolymerization of tri(ethylene glycol) dimethacrylate (EG₃DMA) or its copolymerization with the polar comonomer cyanomethyl methacrylate (CyMA) in the presence of the oligo(ethylene glycol) ethers mentioned above and of the electrolyte LiCF₃SO₃. The gels were characterized concerning their thermal transitions, thermo-mechanical properties, their ability to solvate the electrolyte and their ionic conductivity. In comparison to the linear plasticizers the star-shaped ones show a distinctly lower tendency to crystallize, which is even completely suppressed in several cases. Intensified ion association was found in LiCF₃SO₃ solutions of the star-shaped plasticizers, if the number of the ethylene glycol units per arm was lower than 4. Therefore, the conductivity of the solutions and the gels was lower than that with linear plasticizers at room temperature. The modification of the polymer matrix by copolymerization with 20 mol% CyMA resulted in a maximum of the ionic conductivity σ≈1×10⁻⁵ S/cm of gels with star-shaped plasticizers at 25 °C.     

Infrared spectroscopic and conductivity studies of poly(N-methylpropylenimine)/lithium triflate electrolytes

Poly(propylenimine), PPI, was methylated using Eschweiler-Clark conditions to produce poly(N-methylpropylenimine), PMPI. Differences may be seen in the IR spectra of the PMPI (–CH₂CH₂CH₂NCH₃–) and its homolog poly(N-methylethylenimine), PMEI, (–CH₂CH₂NCH₃–), especially in the conformation region (~ 1100 to ~ 1400 cm^− 1). The addition of lithium trifluoromethanesulfonate, (LiCF₃SO₃), sharpens the distinctions between these systems. Comparison of IR spectra of polymer:LiCF₃SO₃ complexes at compositions ranging from pure polymer to 5:1 N:Li⁺ (molar ratio) suggests significant differences in the nature of polymer salt interactions and the complex structure present in each system. These are further evidenced by differential scanning calorimetry data in which PMPI displays less variation in glass transition temperature, T_g, with the addition of salt than seen in PMEI. These observations may be interpreted in terms of local structural changes originating in cation–anion and cation–polymer interactions, particularly at mid to high salt concentrations.     

Polymer electrolytes based on copolymer of poly(ethylene glycol) dimethacrylate and imidazolium ionic liquid

Polymer electrolytes based on the copolymer of N-vinylimidazolium tetrafluoroborate (VyImBF₄) and poly(ethylene glycol) dimethacrylate (PEGDMA) have been prepared. Ethylene carbonate (EC) and LiClO₄ are added to form gel polymer electrolytes. The chemical structure of the samples and the interactions between the various constituents are studied by FT-IR. TGA results show that these polymer electrolytes have acceptable thermal stability, are stable up to 155 °C. Measurements of conductivity are carried out as a function of temperature, VyImBF₄ content in poly(VyImBF₄-co-PEGDMA), and the concentration of EC and LiClO₄. The conductivity increases with PEGDMA and EC content. The highest conductivity is obtained with a value of 2.90 × 10^? 6 S cm^? 1 at room temperature for VP1/EC(25 wt.%)–LiClO₄ system, corresponding to the LiClO₄ concentration of 0.70 mol kg^? 1 polymer.     

An investigation of the proton conductivities of hydrated poly(vinyl alcohol)/boric acid complex electrolytes

Proton-conducting polymer complex electrolytes were prepared by incorporation of boric acid, H₃BO₃ into poly(vinylalcohol), PVA, to form hydrated PVAxH₃BO₃ where x denotes the number of moles of boric acid per polymer repeat unit. The dried materials were characterized via Fourier transform infrared spectroscopy, thermogravimetry, and X-ray diffraction. The proton conductivity of the hydrated complex electrolytes was measured by AC impedance spectroscopy. PVA2H₃BO₃ with RH ∼25% was found to be optimum composition that exhibited proton conductivity of 1.3 × 10⁻³ S/cm at 80 °C.     

Morphology and conductivity of electrolytes based on poly(ethylene oxide) - Eu(ClO4)3 films

Solid polymer electrolytes based on a poly(ethylene oxide), (PEO), host have been prepared using the solvent casting method and characterized by conductivity measurements and thermal analysis. The observed ionic conductivity of the novel system based on PEO and europium perchlorate was similar to that of other electrolytes based on the same polymer host with a different trivalent guest species [1]. The presence of the perchlorate anion widened the composition range of amorphous behaviour but limited the thermal stability of the electrolytes produced. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Ionic conductivity of electrolytes based on star-branched poly(ethylene oxide) with high concentration of lithium salts

Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone)imide LiTFSI and lithium iodide salts were prepared by casting from solution. The electrical properties of electrolytes subjected to various heating and cooling runs were studied by impedance spectroscopy and impedance spectroscopy simultaneous with optical microscope observation. Differential scanning calorimetry was used for additional characterization. The results indicate that in electrolytes with high content of salt, values of ionic conductivity comparable to that of dilute electrolytes can be achieved. Moreover, electrolytes with high amount of salt seem to show weaker temperature dependence of conductivity. Promising results in terms of ionic conductivity were obtained for mixture of LiTFSI and lithium iodide. A few problems which may decrease the performance of studied system as a solid electrolyte were also identified, from which changes of physical properties of samples subjected to thermal cycles and aging seem to be the most important ones.     

Synthesis, characterization and electrochemical properties of poly(methyl methacrylate)-grafted-poly(vinylidene fluoride-hexafluoropropylene) gel electrolytes

A new comb-like copolymer, poly(vinylidene fluoride-co-hexafluoropropylene)-g-poly(methyl methacrylate), or [P(VDF-HFP)-g-PMMA], was successfully synthesized through grafting in situ formed PMMA to the P(VDF-HFP) backbone. The composition of the P(VDF-HFP)-g-PMMA copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and elemental analysis. X-Ray diffractometry (XRD) and differential scanning calorimetry (DSC) were used to examine the reduction in crystallinity of P(VDF-HFP) due to the anchoring of PMMA segments on it. Gel electrolyte membranes based on the resulting copolymer were prepared by the Bellcore process. The ionic conductivity of Li⁺ across the membranes and the related transference number were measured. A study of the interfacial stability between Li electrode and the P(VDF-HFP)-g-PMMA gel electrolyte was also conducted to evaluate the suitability of the P(VDF-HFP)-g-PMMA copolymer in rechargeable lithium and lithium-ion battery applications.     

Ionic conductivity and interfacial resistance of electrospun poly(acrylonitrile)/poly(methyl methacrylate) fibrous membrane-based polymer electrolytes for lithium ion batteries

Electrospun poly(acrylonitrile) fibrous membrane (PAN-EFM) is prepared and enhanced by adding poly(methyl methacrylate)(PMMA) and subsequently minimizing the average diameter of the PAN/PMMA blend fibers. Electrospinning of the 50/50 wt% PAN/PMMA solution is carried out with the aim of the simultaneous presence of both polymers on the fiber surface. Their presence in exterior surface is confirmed using the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique next to the leaching of PMMA with acetone. The process parameters are optimized in four stable modes with the average diameter decreasing from 445 to 150 nm. Mechanical strength of the membrane is measured and reported. Comparing the sample electrochemical properties of the EFMs reveals that the addition of PMMA increases ionic conductivity from 1.02 to 3.31 mS cm^?1 and reduces interfacial resistance from ~1000 to ~400?Ω. It is also demonstrated that the ~300-nm reduction in average diameter of the blend fibers increases ionic conductivity from 3.31 to 5.81 mS cm^?1 and reduces interfacial resistance from ~400 to ~200?Ω.     

Rheological,thermal, and mechanical properties of poly(ethylene naphthalate)/poly(ethylene terephthalate) blends

Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and ¹H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content.     

Preparation of poly(2-ethyl aniline)/kaolinite composite materials and investigation of their properties

Conductive poly(2-ethyl aniline) (PEAn)/kaolinite composite was prepared by chemical polymerization in aqueous HCl medium in the presence of kaolinite particles by using potassium chromate (K₂CrO₄) as oxidant. Effects of polymerization conditions, such as concentrations of oxidant and 2-ethyl aniline, polymerization time and temperature on PEAn content and conductivity of composite, were investigated. The prepared composite material, having the highest PEAn content and conductivity, was obtained in the polymerization carried out at 20 °C for 2 h with 0.2 M K₂CrO₄ and 0.2 M EAn. It was observed that the micro-hardness of prepared composites increased with the increase in the PEAn contents of composites. The highest micro-hardness value of 7.92 kg mm⁻² was reached at 24.6% PEAn content. Characterization of composites was carried out by FTIR spectroscopy, XRD, TGA and SEM techniques.     

An experimental study on the effect of mesoporous silica addition on ion conductivity of poly(ethylene oxide) electrolytes

Solid polymer electrolyte (SPE) composites, which are composed of poly(ethylene oxide) (PEO), mesoporous silica (SBA-15), and lithium salt were prepared in order to investigate the influence of SBA-15 content on the ionic conductivity of the composites. The ionic conductivity of the SPE composites was monitored by frequency response analyzer (FRA), and the crystallinity of the SPE composites was evaluated by using XRD. As a result, the addition of SBA-15 to the polymer mixture inhibited the growth of PEO crystalline domain, due to the mesoporous structure of the SBA-15. Also, the PEO₁₆LiClO₄/SBA-15 composite electrolytes show an increased ion conductivity as a function of SBA-15 content up to 15 wt.%. These ion conductivity characteristics are dependent on crystallinity with SBA-15 content.     

Poly(ethylene glycol) and phospholipid packing in the structure of reverse micelles

The influence of water substitution by a substance with a different polarity on the structure of phospholipid monolayer interface in water-in-oil microemulsion has been studied by the Fourier-transform pulsed-gradient spin-echo (FT PGSE)¹H nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spin-label methods. For this purpose the soybean phosphatidylcholine-based microemulsion and water soluble poly(ethylene glycol) with molecular weight 400 (PEG400) were used. Self-diffusion coefficients of all microemulsion components obtained by the FT PGSE NMR technique provided information about both the size of reverse micelles and distribution of components between different microemulsion compartments. The maximum hyperfine splitting, 2A _max, in the ESR spectra was used to characterize the degree of the phospholipid hydrocarbon chain mobility. It was shown that PEG400 alters significantly the size of the reverse micelles and the motion of the labeled segments of the lipid tails. A mechanism of PEG400 acting in solution of the phospholipid-based reverse micelles on the basis of the rough decrease of the micelle core polarity was suggested.     

MEH-PPV/PEG聚合物电双稳器件的研究

将PEG(聚乙二醇)引入到ITO/MEH-PPV(聚(2-甲氧基,5(2'-乙基己氧基)-1,4-苯撑乙烯撑)/Al三明治器件中,实现了很好的电双稳性能。通过改变PEG的分子量、浓度以及退火温度等条件,对器件性能进行了优化。通过电流-电压(I-V)测试研究了不同器件的性能,结果表明,分子量为4 000的PEG,在30 mg/mL的浓度下,通过120℃退火制备的薄膜,其器件性能最优,电流开关比可以达到10~3以上。利用SEM测试研究了活性层的膜形貌,并结合电流-电压(I-V)曲线的线性拟合,分析了电荷在器件中的传输过程。研究发现,相分离产生的陷阱对电荷的俘获是该器件产生电双稳特性的主要原因。     

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.     

Stimuli-responsive poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) triblock copolymers and complexation with poly(acrylic acid) at low pH

The self-organization of the double hydrophilic triblock copolymer poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide), PEO-b-P2VP-b-PEO, was investigated in dilute aqueous solution under several experimental conditions using turbidimetry, as well as static and dynamic light scattering. As a result of the temperature-sensitive properties of the end PEO blocks and the p H-responsive properties of the middle P2VP block, the formation of large star-like micellar nanostructures is observed at high p H, while at low p H, but in the presence of salt and at high temperature, flower-like micelles are formed. Moreover, the viscosimetric and dynamic light scattering studies at low p H revealed that micelle-like nanostructures are formed upon mixing the triblock copolymer with poly(acrylic acid), PAA, due to hydrogen bonding interpolymer complexation.     

Properties of acrylonitrile butadiene rubber (NBR)/poly(lactic acid) (PLA) blends and their foams

Abstract

Thermoplastic elastomers and their foams were prepared by blending elastomeric acrylonitrile butadiene rubber (NBR) and rigid poly(lactic acid) (PLA) with various PLA compositions ranging between 0 and 40%. The thermal and mechanical properties and the morphologies of the blends with various PLA contents were investigated through universal testing machine, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscope analysis. The rheological properties during gel formation were in situ monitored through the evolution of torque with curing time. Furthermore, the microcellular structures and physical properties of the NBR/PLA foams prepared using organic blowing agents were studied. The NBR/PLA blends showed a two-phase morphology made of a continuous NBR matrix and micron or submicron nodules and the tensile strength and modulus; also, hardness of the NBR/PLA blends increased with the increase of the added PLA content. While the foamed samples exhibited a similar cell structure and foaming ratio to that of the pure NBR, the cell formation was considerably reduced as the added PLA content exceeded 30%. We conclude that the mechanical properties of NBR thermoplastic elastomer as well as its foams can be controlled by a judicious introduction of rigid and biodegradable PLA.     

The conductivity and dielectric studies of solid polymer electrolytes based on poly (acrylamide-co-acrylic acid) doped with sodium iodide

Solid polymer electrolyte thin films based on polyacrylamide-co-acrylic acid (PAAC) doped with sodium iodide (NaI) with different ratios of polymer and salt added with fixed amount of additive of propylene carbonate (PC) were prepared by using solution casting method. The PC was added to the mixture of the solution to provide more flexibility to the polymer film by increasing the plasticity of the thin film membrane. The conductivity and dielectric studies were carried out on these thin films to understand the ion transport properties of the polymer electrolytes. The highest conductivity obtained was 1.88?×?10^?5 S cm^?1 for the 30% NaI salt-doped polymer electrolyte system at room temperature. The temperature-dependent conductivity agrees with Arrhenius relationship which shows that hopping mechanism of ions in the polymer matrix. The dielectric properties especially the loss tangent used to analyze the segmental relaxation of the polymer chain as more concentration of salt was incorporated. The electric modulus was studied to understand the electrical relaxation processes to overcome electrode polarization effect.     

Upon a magnetic composite preparation based on magnetite and poly(succinimide)-b-poly(ethylene glycol) shell

Taking into account that magnetic particles with suitable surface characteristics have a high potential for the use in a lot of in vitro and in vivo applications, in the study is presented the in situ preparation of a core-shell magnetic composite based on the magnetite core and the shell composed from the poly(succinimide)-b-poly(ethylene glycol) copolymer. The average particle size of the synthesized magnetic microspheres is in the range of 6.5-8.8 μm with a magnetite content of around 11%. The saturation magnetization of the microspheres was found 26.8 emu/g, the magnetic microspheres being characterized by superparamagnetic properties. The particles have combined properties of high magnetic saturation and biocompatibility and interactive functions at the surface through the block copolymer shell. The surface of the magnetic particles has also the possibility for further functionalization or the attachment of various bioactive molecules after the hydrolysis of the succinimide cycle and the resulting carboxylic group.