Facile preparation of poly(3,4‐ethylenedioxythiophene) nanoparticles via a miniemulsion polymerization process

Poly(3,4‐ethylenedioxythiophene) (PEDOT) nanoparticles were prepared via a miniemulsion polymerization process. The chemical oxidative polymerization of 3,4‐ethylenedioxythiophene (EDOT) occurred in the presence of β‐1,3‐glucan with the injection of an aqueous oxidant solution, and the nanodroplets of EDOT were transformed to PEDOT nanoparticles dispersed in the aqueous medium. The aqueous emulsion of PEDOT nanoparticles showed relatively long emulsion stability (> 8 weeks), and the recovered solid nanoparticles were also redispersible in deionized water without deposition. The size and size distribution of PEDOT nanoparticles could be controlled by adjusting the operating conditions of the ultrasonifier before the polymerization process. The building‐up of a shearing force decreases the size of the PEDOT nanoparticles and also causes the occurrence of a multimodal size distribution for the PEDOT nanoparticles. The electrical conductivity of the PEDOT nanoparticles was 0.28–1.20 S cm⁻¹. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Nafion/PTFE Composite Membranes for Fuel Cell Applications

The composite membranes were prepared by impregnation of porous poly(tetrafluoroethylene) membranes with a 5 wt% Nafion solution. Scanning electron microscope micrographs of composite membranes show the surface and cross section of poly(tetrafluoroethylene) membranes were covered and filled with Nafion resin. Comparison of physical properties and fuel cell performance of composite membranes with those of Nafion membranes (DuPont Co) is presented. The composite membrane has better thermal stability and gas barrier property but worse ionic conductivity than Nafion membrane. Though the composite membrane has a lower conductivity than Nafion membrane, however, owing to the thinner thickness of composite membrane (in thickness of 20±5µm) than Nafion-115 (in thickness of 125µm) and Nafion-117 (in thickness of 175µm) membranes, the composite membrane has a shorter H⁺ ion transporting pathway and thus a higher conductance (conductance = conductivity/membrane thickness) than Nafion-115 and Nafion-117 membranes. Thus the composite membrane has a better fuel cell performance than Nafion-117 and Nafion-115 membranes. In this report, we show that our composite membrane has a fuel cell performance similar to Nafion-112 membrane (in thickness of 50µm).     

Evidence for ‘bottom up’ growth during vapor phase polymerization of conducting polymers

Elemental analysis of sequentially formed PPy/PEDOT polymer blends using liquid-like oxidant layers by vapor phase polymerization (VPP) has provided conclusive evidence for a ‘bottom up’ growth mechanism during polymerization. Chemical analysis by XPS of the top surface of the polymer thin film formed by sequential polymerization of pyrrole monomer, followed by EDOT monomer, revealed the outer most layer to be PEDOT. ToF-SIMS depth profiling confirmed this result, indicating the diminishing presence of PEDOT fragments with concomitant increasing PPy fragments as a function of depth from the top surface, an indication that PEDOT was stationed above PPy. When the polymerization process was reversed (i.e. EDOT followed by pyrrole) the opposite was observed. By extension we propose that the same growth mechanism exists for any VPP conducting polymer where a (viscous) liquid-like oxidant layer is utilized.     

聚3,4-乙烯二氧噻吩/聚苯胺复合材料的制备与性能

以过硫酸铵(APS)和FeCl3为复合氧化剂,采用原位化学氧化聚合法合成了导电聚3,4-乙烯二氧噻吩/聚苯胺(PEDOT/PANI)复合材料,研究了苯胺浓度及加入时间、复合氧化剂配比和复合乳化剂配比对复合材料性能的影响,并对复合材料进行了分析. 结果表明,PEDOT/PANI复合材料合成的较佳工艺条件为：3,4-乙烯二氧噻(EDOT) 0.6 mol/L、复合氧化剂 0.6 mol/L(FeCl3:APS=1:2, mol)、复合乳化剂 0.4 mol/L(SDBS:CTAB=2:3, mol)、复合掺杂剂1.2 mol/L(H2SO4:SSA=4:1, mol)及苯胺0.8 mol/L, EDOT聚合2 h后加入苯胺溶液继续反应8 h. 复合材料的导电性、结晶性和热稳定性比纯导电聚合物好.     

A Fuel‐Flexible Alkaline Direct Liquid Fuel Cell

We constructed a fuel‐flexible fuel cell consisting of an alkaline anion exchange membrane, palladium anode, and platinum cathode. When an alcohol fuel was used with potassium hydroxide added to the fuel stream and oxygen was the oxidant, the following maximum power densities were achieved at 60 °C: ethanol (128 mW cm⁻²), 1‐propanol (101 mW cm⁻²), 2‐propanol (40 mW cm⁻²), ethylene glycol (117 mW cm⁻²), glycerol (78 mW cm⁻²), and propylene glycol (75 mW cm⁻²). We also observed a maximum power density of 302 mW cm⁻² when potassium formate was used as the fuel under the same conditions. However, when potassium hydroxide was removed from the fuel stream, the maximum power density with ethanol decreased to 9 mW cm⁻² (using oxygen as oxidant), while with formate it only decreased to 120 mW cm⁻² (using air as the oxidant). Variations in the performance of each fuel are discussed. This fuel‐flexible fuel cell configuration is promising for a number of alcohol fuels. It is especially promising with potassium formate, since it does not require hydroxide added to the fuel stream for efficient operation.     

Preparation of anion exchange membranes based on pyridine functionalized poly(vinyl alcohol) crosslinked by 1,4-dichlorobutane

A series of anion exchange membranes [pyridine functionalized-poly(vinyl alcohol)-1,4-dichlorobutane (PVA-PY-DL_x)] were synthesized by using PVA-PY as polymer matrix and DL as crosslinker and iodomethane as quaternization reagent. During the experiment, pyridine groups grafted on PVA were transformed into quaternary ammonium group during the formation process of the crosslinked structure and the quaternization routine by iodomethane. The characterization results revealed that the PVA-PY-DL_x membranes have been successfully prepared and the crystallinity increases with increase of DL. PVA-PY-DL_x membranes have smooth and uniform morphology. The introduction of crosslinked structure improves the mechanical properties and dimensional stability of the PVA-PY-DL_x membrane, enhances the alkali resistance. When the mass content of DL was 4.0%, composite membrane had the maximum tensile strength (44.2 MPa), and the OH⁻ conductivity reaches 1.05 × 10⁻² S cm⁻¹ at 70 °C. The accelerated aging experiment was carried out in 3 mol L⁻¹ potassium hydroxide (KOH) solution for 120 h at 80 °C, which revealed that the anionic conductivity of PVA-PY-DL_4.0 membrane retains 79.6% of its initial conductivity, showing better stability of alkali stability. Methanol permeability of PVA-PY-DL_x membranes was only the 0.37–0.72% of the Nafion-117 membrane in 3 mol L⁻¹ methanol at 60 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47395.     

New solid polymer electrolyte membranes for alkaline fuel cells

New solid polymer electrolyte composite membranes have been prepared using chitosan as matrices and incorporating potassium hydroxide as the functional ionic source. These membranes were featured as a three‐layer structure having a porous intermediate layer while the two crosslinked surface layers are dense. Results from impedance spectroscopy analysis showed that the conductivity of some hydrated composite membranes, after hydration for 1 h at room temperature, reached about 10⁻² S cm⁻¹. Several composite membranes were then tested in alkaline fuel cells, using hydrogen as fuel, air as oxidant and platinum as the electrode catalyst. A current density of 35 mA cm⁻² has been achieved at 60 °C with a flow rate of hydrogen at 50 ml min⁻¹ and air at 200 ml min⁻¹. Copyright © 2004 Society of Chemical Industry     

Nafion® reinforced with polyacrylonitrile/ZrO2 nanofibers for direct methanol fuel cell application

Nafion® membrane blended with polyacrylonitrile nanofibers decorated with ZrO₂ was successfully fabricated. The composite membrane showed improved proton conductivity, swelling ratio, thermal and mechanical stability, reduced methanol crossover, and enhanced fuel cell efficiency. The nanocomposite membranes achieved a reduced methanol crossover of 5.465 × 10⁻⁸ cm² S⁻¹ compared to 9.118 × 10⁻⁷ cm² S⁻¹ of recast Nafion® membrane using a 5 M methanol solution at 80°C. The composite membrane also showed an ion conductivity of 1.84 compared to 0.25 S cm⁻¹ recast Nafion® at 25°C. The composite membranes showed a peak power density of 68.7 mW·cm⁻² at 25°C, these results show a promising composite membrane for fuel cell application.     

Fuel cell performance of polymer electrolyte membrane based on hexafluorinated sulfonated poly(ether sulfone)

The potential-current fuel cell characteristics of membrane electrode assemblies (MEAs) using hexafluorinated sulfonated poly(ether sulfone) copolymer are compared to those of Nafion^® based MEAs in the case of proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC). The hexafluorinated copolymer with 60 mol% of monosulfonated comonomer based acid form membrane is chosen for this study due to its high proton conductivity, high thermal stability, low methanol permeability, and its insolubility in boiling water. The catalyst powder is directly coated on the membrane and the catalyst coated membrane is used to fabricate MEAs for both fuel cells. A current density of 530 mA cm^?2 at 0.6 V is obtained at 70 °C with H₂/air as the fuel and oxidant. The peak power density of 110 mW cm^?2 is obtained at 80 °C under specific DMFC operating conditions. Other electrochemical characteristics such as electrochemical impedance spectroscopy, cyclic voltammetry, and linear sweep voltammetry are also studied.     

The structure and properties of PEDOT synthesized by template-free solution method

In this study, a simple one-step template-free solution method was developed for the preparation of poly(3,4-ethylenedioxythiophene) (PEDOTs) with different morphologies by adjusting various ratios of oxidant (FeCl₃·6H₂O) to monomer (3,4-ethylenedioxythiophene (EDOT)). The results from structural analysis showed that the structure of PEDOT was strongly affected by the oxidant/monomer ratio, and the polymerization degree, conjugation length, doping level, and crystallinity of PEDOT decreased with increasing of the oxidant/monomer ratio. The morphological analysis showed that PEDOT prepared from an oxidant/monomer ratio of 3:1 displayed a special coral-like morphology, and the branches of ‘coral’ would adjoin or grow together with increasing content of oxidant in the reaction medium; consequently, the morphology of PEDOT changed from coral to sheets (at an oxidant/monomer ratio of 9:1). The electrochemical analysis proved that the PEDOT prepared from an oxidant/monomer ratio of 3:1 had the lowest resistance and the highest specific capacitances (174 F/g) at a current density of 1 A/g with a capacity retention rate of 74% over 1,500 cycles, which indicated that the PEDOT with a coral-like morphology could be applied as a promising electrode material for supercapacitors.     

Ionically Cross‐Linked Proton Conducting Membranes for Fuel Cells

For improving stability without sacrificing ionic conductivity, ionically cross‐linked proton conducting membranes are fabricated from Na⁺‐form sulfonated poly(phthalazinone ether sulfone kentone) (SPPESK) and H⁺‐formed sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO). Ionically acid‐base cross‐linking between sulfonic acid groups in SPPO and phthalazone groups in SPPESK impart the composite membranes the good miscibility and electrochemical performance. In particular, the composite membranes possess proton conductivity of 60–110 mS cm⁻¹ at 30 °C. By controlling the protonation degree of SPPO within 40–100 %, the composite membranes with favorable cross‐linking degree are qualified for application in fuel cells. The maximum power density of the composite membrane reaches approximately 1100 mW cm⁻² at the current density of 2800 mA cm⁻² at 70 °C.     

聚乙撑二氧噻吩/二氧化硅复合材料制备及导电性研究

以表面含磺酸基团的改性二氧化硅纳米微球为填料,以三氯化铁(FeCl3)为氧化剂,对甲苯磺酸钠(TSANa)为掺杂剂,氧化聚合乙撑二氧噻吩(EDOT),制备了具有良好导电性的PEDOT/SiO2复合材料。并利用X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和四探针等手段进行了表征。结果表明:当FeCl3与EDOT的摩尔比为0.8,TSANa的质量分数为10%,反应时间为4 h,得到的复合材料具有较高的电导率。     

Sulfonated poly(ether ether ketone)/s–TiO2 composite membrane for a vanadium redox flow battery

The SPEEK/s-TiO₂ composite membrane was prepared by blending sulfonated poly(ether ether ketone) (SPEEK) and sulfonated titanium dioxide (s-TiO₂) nanoparticles. The important physiochemical parameters such as proton conductivity, water uptake, swelling degree and ion exchange capacity of the composite membrane were measured. The thermal stability and chemical stability were also tested. It was observed that the SPEEK/s-TiO₂ composite membrane exhibited the best selectivity (7.13 × 10⁴ S·min·cm⁻³) accompanying high proton conductivity (0.061 S·cm⁻¹) and low tetravalent vanadium ion (VO²⁺) permeability (8.55 × 10⁻⁷ cm²·min⁻¹) compared with Nafion117, SPEEK and SPEEK/TiO₂ membranes. The battery performance with these membranes was characterized by charge–discharge cycling tests and it was found that the SPEEK/s-TiO₂ composite membrane showed the highest energy efficiency (EE) up to 82.3%, indicating the SPEEK/s-TiO₂ composite membrane is a candidate for vanadium redox flow battery (VRFB) application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48830.     

Preparation and characterization of graphene composites with conducting polymers

We report a new route for preparing electro‐conductive composites based on reduced graphene oxide (RG‐O) and poly(3,4‐ethylenedioxythiophene) (PEDOT). The composites were prepared by in situ polymerization of EDOT in aqueous mixture containing RG‐O platelets modified with poly(sodium 4‐styrenesulfonate) (PSS). In the synthetic process, PSS molecules stabilize RG‐O in the aqueous phase and function as a polymerization template to hybridize PEDOT chains along RG‐O platelets. Compared with the RG‐O platelets, the resulting composites show an enhanced electrical conductivity of 9.2 S cm^?1 with good thermal stability. Copyright © 2011 Society of Chemical Industry     

New composite membrane poly(vinyl alcohol)/graphene oxide for direct ethanol–proton exchange membrane fuel cell

This study investigated a simple synthesis of a crosslinked poly(vinyl alcohol)/ graphene oxide composite membrane with lower ethanol permeability membrane for passive direct ethanol–proton exchange membrane fuel cells (DE-PEMFCs). The chemical and physical structure, morphologies, ethanol uptake and permeability, ion exchange capacities, water uptake, and proton conductivities were determined and found that transport properties of the membrane were affected by the GO loading. The composite membrane with optimum GO content (15 wt %) exhibited the highest proton conductivity of 9.5 × 10⁻³ Scm⁻¹ at 30°C, 3.24 × 10⁻² Scm⁻¹ at 60°C, respectively and reduced ethanol permeability until 1.75 × 10⁻⁷ cm² s⁻¹. In the passive DE-PEMFC, the power density at 60°C were obtained as 5.84 mW cm⁻² higher than those by commercial Nafion 117 is 4.52 mW cm⁻². © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46928.     

A new proton conducting membrane based on copolymer of methyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid for direct methanol fuel cells

In this paper, a new kind of copolymer methyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS-co-MMA) was synthesized by free radical polymerization. IR-spectrum and ¹H NMR were used to confirm the structure of the copolymers, and the thermal character of the copolymers was investigated with TGA and DSC. Flexible and transparent membranes based on this kind of copolymer were prepared by solution casting method. The physical properties including ionic exchange capability (IEC), water uptake, proton conductivity, methanol permeability and morphology of the membranes were investigated. These membranes showed higher water uptake though they had lower IEC compared with Nafion-117. The proton conductivity of the membrane with IEC of 0.9 mmol/g was 1.14 × 10⁻² S/cm and its methanol permeability coefficient was 5.46 × 10⁻⁷ cm²/s, much lower than that of Nafion-117. Tests on cells were also carried out to measure the performance of the membrane.     

Preparation of composite membranes with polyimides and poly (amide-imide)s skin via interfacial condensation for air separation

Composite membranes were prepared by the interfacial condensation of water-soluble diamines with an organic solvent (dichloromethane)-soluble dicarbo-methoxy terephthaloyl chloride or carbomethoxy terephthaloyl chloride on top of a porous aluminum oxide support. The morphology of skin on the composite membranes is different in the two different procedures. The polyimide composite membranes with 40-times coatings provide a high gas permeation rate of oxygen and good permselectivity [α(O₂/N₂)]. The composite membrane with the polyimides skin at 40-times coatings had a gas permeation rate of oxygen range from 83 × 10⁻⁵ to 130 × 10⁻⁵ cm³(STP) s⁻¹ cm⁻² cmHg⁻¹, and a permselectivity [α(O₂/N₂)] range of 3.57 to 5.60. The composite membrane with poly (amide-imide)s skin at 40-times coatings had a gas permeation rate of oxygen range from 102 × 10⁻⁵ to 146 × 10⁻⁵ cm³(STP) s⁻¹ cm⁻² cmHg⁻¹, and the permselectivity (α(O₂/N₂)) range from 3.20 to 4.96.     

Novel Proton Conducting Membranes from the Combination of Sulfonated Polymers of Polyetheretherketones and Polyphosphazenes Doped with Sulfonated Single‐Walled Carbon Nanotubes

Intent on developing efficient proton exchange membranes used for direct methanol fuel cells as well as hydrogen fuel cells, a series of membranes based on sulfonated polyetheretherketone and sulfonated polyphosphazene‐graft copolymers is prepared by cross‐linking reaction because the former material has good enough mechanical property, while the latter is excellent in the proton transfer. The cross‐linked membranes combine the advantages of the two kinds of polymers. Among them, the membrane poly[(4‐trifluoromethylphenoxy)(4‐methylphenoxy)phosphazene]‐g‐poly {(styrene)₁₁‐r‐[4‐(4‐sulfobutyloxy)styrene]₃₃‐sulfonated poly(ether ether ketone)75 (CF₃‐PS₁₁‐PSBOS₃₃‐SPEEK75) shows a proton conductivity at 0.143 S cm⁻¹ under fully hydrated conditions at 80 °C and performs tensile strength about five times as much as did the sulfonated polyphosphazene membrane CF₃‐PS₁₁‐PSBOS₃₃. Further doping of sulfonated single‐walled carbon nanotubes (S‐SWCNTs) into the cross‐linked membranes on the screening of additives gives composite membrane CF₃‐PS₁₁‐PSBOS₃₃‐SPEEK75‐SWCNT possessing proton conductivity of 0.196 S cm⁻¹, even higher than that of Nafion 117 and a tensile strength comparable to that of Nafion 117. However, this significance of the composite membrane in the proton conduction is not observed in the test with a H₂/air fuel cell when it shows a maximal power density of 280 mW cm⁻² at 80 °C, whereas 294 mW cm⁻² is observed for CF₃‐PS₁₁‐PSBOS₃₃‐SPEEK75.

     

Radiation-grafted membrane/electrode assemblies with improved interface

Recent progress is reported in preparing membrane/electrode assemblies for polymer electrolyte fuel cells based on radiation-grafted FEP-g-poly(styrenesulfonic acid) membranes. MEAs with an improved interface between the membrane and commercially available gas diffusion electrodes were obtained by Nafion®-coating of the membrane and hot-pressing. These improved MEAs showed both, performance data comparable to those of MEAs based on Nafion® 112 and an operation lifetime in H₂/O₂ fuel cells of more than 2000 h at 60 °C and 500 mA cm⁻² current density.     

Influence of different organic solvents and oxidants on insulating and film-forming properties of PEDOT polymer

Processing of conjugate polymers has always been a challenge because of their poor solubility and infusibility in organic and inorganic solvents. The processibility and applications of intrinsically conductive polymers can be enhanced by producing their solutions or dispersions in different suitable solvents. It can also be achieved by preparing undoped or electrically neutral polymers, which can further be transformed in a semiconductor after an oxidation/reduction reaction. The present study focuses on the preparation of active dispersions of poly(3,4-ethylenedioxythiophene) (PEDOT) conductive polymer in various organic solvents. For this purpose, the polymerization of 3,4-ethylenedioxythiophene (EDOT) monomer was carried out in three different organic solvents, ethanol, 1-butanol, and acetonitrile, with two commonly used oxidants, ferric(III) chloride and ferric(III) p-toluenesulfonate. In this regard, the oxidant and monomer solutions with variable molar concentrations (0.25, 0.5, and 1.0 M) were prepared in particular solvents and then the solutions were mixed with different monomer/oxidant volume ratios. The obtained dispersions of PEDOT can readily be polymerized on the surface of different materials after solvent evaporation and a uniform film can be achieved. The effect of molar as well as volume concentrations of EDOT monomer and oxidant on insulating (undoped/neutral) and film-forming properties of PEDOT was investigated. These dispersions were applied on a transparent PET film and cellulosic fibers (viscose), dried at room temperature and analyzed using scanning electron microscope, optical microscope, and ATR-FTIR spectroscopic analysis. The electrical characterization of undoped PEDOT-coated fibers was performed on Keithley Picoammeter. This study contributes to obtaining a simpler and instantaneous polymerization method of PEDOT preparation and enhancing its application area.