Polypyrroles with Nafion

Polypyrrole containing other non-classical counteranions have been prepared [231]. These anions are transition metal anions such as cyanides, FeCl4", metallophtalocyanine, trisoxalates, EDTA, SALEN, dithiolates and polytungstates. The use of polymeric anions [232,233] has led to polypyrroles with good mechanical properties though with lower conductivity (<1 S cm ). With Nafion [234,235] sulfonate is the counteranion so that better mechanical properties are obtained. 

Anodic deposition of polypyrrole onto ITO or gold electrodes coated with Nafion produced a blend at the... 

After electrodeposition, the ITO covered with polypyrrole was immersed in deionized water for 30 min, next allowed to dry for 12 h and Anally was placed into 6 M NaOH solution for 30 s. According to the authors, the last operatiOTi reduced the conductivity of polypyrrole by several orders of magnimde and increased its stability. Occasionally polypyrrole film was additionally covered with Nafion layer to block the ingress of anions. 

Yoon el al. [112] reported an all-solid-state sensor for blood analysis. The sensor consists of a set of ion-selective membranes for the measurement of H+, K+, Na+, Ca2+, and Cl. The metal electrodes were patterned on a ceramic substrate and covered with a layer of solvent-processible polyurethane (PU) membrane. However, the pH measurement was reported to suffer severe unstable drift due to the permeation of water vapor and carbon dioxide through the membrane to the membrane-electrode interface. For conducting polymer-modified electrodes, the adhesion of conducting polymer to the membrane has been improved by introducing an adhesion layer. For example, polypyrrole (PPy) to membrane adhesion is improved by using an adhesion layer, such as Nafion [60] or a composite of PPy and Nafion [117],... 

Treatment of PVDF by dehydrofluorination and doping with sulfuric acid prior to blending have been shown to improve the hydrophilicity of a Nafion/PVDF blend. Such blends were demonstrated to show comparable conductivity and FC performance to unmodified Nation and significantly improved over blends in which the PVDF had not been treated. MeOH crossover rates, however, were not reported. PEMs composed of "sandwiches" of Nation plus Nafion/PVDF blends have also been used as PEMs in order to reduce MeOH crossover and improve DMFC performance. - Other non-ionic polymers that have been blended with Nation include PPCF and polypyrrole. 21... 

Additional improvements can be achieved through the use of multilayers (based on different overlaid films). Such combination of the properties of different films has been documented with bilayers of Nation/CA (14) and Nafion/collagen (29). The former allows selective measurements of the neurotransmitter dopamine in the presence of the slightly larger epinephrine and the anionic ascorbic acid (Figure 5). In addition to bilayers, mixed (composite) films, such as PVP/CA (75) or polypyrrole/Eastman Kodak AQ (30) layers can offer additional permselectivity advantages, such composites exhibit properties superior to those of their individual components. Also promising are sensor arrays, based on electrodes coated with... 

Composites between polypyrrole and a variety of porous materials such as paper, cloth or wood have been made. Often the respective material was impregnated with an oxidant such as FeCls and subsequently contacted with pyrrole vapor or solution. For example, polypyrrole (and polyaniline) have been made in Nafion perfluorosulfonated ionomer membranes by treatment with aqueous ferric chloride and the monomers. ... 

Yogeswaran et al., designed a new bimetallic nanoparticles (Au and Pt) modified electrodes for simultaneous determination of AA, EP and UA [169], First, a composite film comprising of functionalized multiwall carbon nanotubes and nafion was formed on the GC electrode. Then Au and Pt NPs were electrochemically deposited on to the composite film modified GC electrode. The voltammetric peaks of AA, EP and UA are well resolved with the peak separations of 222 mV and 131 mV respectively. Lu et al., demonstrated the determination of UA on GC electrode electrodeposited with AuNPs and DNA [170], Clean GC electrode was immersed into a AuNPs colloidal solution and a potential of +1.5 V is applied for 60 min for the deposition of AuNPs. Then the electrode was dipped into a DNA solution (0.1 mg/ml) and a potential of +1.5 V is applied for 30 min to electrodeposit DNA. Finally, DNA/AuNPs modified electrode excellently separates the voltammetric signals of UA, NEP and AA. Li et al., electrodeposited AuNPs on the GC electrode modified with the ultrathin overoxidized polypyrrole film [171], The modified determines the UA in the presence of EP and AA with a lowest detection limit of 1.2 x 10"8 M. 

The use of PPy-Nafion-PPy trilayers has enabled a low-power pump to be constructed at Dublin in which two trilayers act as tweezers in compressing the fluid inside a flexible polyurethane tube. Through the choice of conical inlets and outlets to create unidirectional fluid movement, flow rates of up to 1.6 pi s were achieved [96]. A further pmnp design involving a polypyrrole-polydimethylsiloxane diaphragm with check valves has been developed, with a pumping rate of 52 pi min [97],... 

The most studied Nafion composite membranes with organic fillers include blends of Nafion with polypyrrole, polybenzimidazole, poly(vinyl alcohol), polyvinylidene fluoride, polyanfline, sulftmated poly(ether ether ketone), and poly(tetrafluoroethylene). 

The acid-base Nafion composite membranes include blends of Nafion with polypyrrole (PPy) [98-104], polybenzimidazole (PBI) [105-107], poly (propyleneoxide) (PPO) [108, 109], polyfurfuryl alcohol (PFA) [110], poly(vinyl alcohol) (PVA) [111-115], sulfonated phenol-formaldehyde (sPF) [116], polyvinylidene fluoride (PVdF) [117-122], poly(p-phenylene vinylene) (PPV) [123], poly(vinyl pyrrolidone) (PVP) [124] polyanifine (PANI) [125-128], polyethylene (PE) [129], poly(ethylene-terephtalate) [130], sulfated p-cyclodextrin (sCD) [131], sulfonated poly(ether ether ketone) (sPEEK) [132-135], sulfonated poly(aryl ether ketone) (sPAEK) [136], poly(arylene ether sulfone) (PAES) [137], poly(vinylimidazole) (PVl) [138], poly(vinyl pyridine) (PVPy) [139], poly (tetrafluoroethylene) (PTFE) [140-142], poly(fluorinated ethylene-propylene) [143], sulfonated polyhedral oligomeric silsesquioxane (sPOSS) [144], poly (3,4-ethylenedioxythiophene) (PEDT) [145, 146], polyrotaxanes (PR) [147], purple membrane [148], sulfonated polystyrene (PSSA) [149, 150], polystyrene-b-poly(ethylene-ran-butylene)-bpolystyrene (SEES) [151], poly(2-acrylamido-2-methyl-l-propanesulphonic acid-co-l,6-hexanediol propoxylate diacrylate-co-ethyl methacrylate) (AMPS) [152], and chitosan [31]. A binary PVA/chitosan [153] and a ternary Nafion composite with PVA, polyimide (PI) and 8-trimethoxy silylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS) has also been reported [154]. 

Park et al. [102] reported a noticeable reduction of the methanol uptake in Nafion/polypyrrole composite membranes, which is accompanied by a similar decrease in the water sorption. A Nafion/polyaniline membrane containing polyanilines with different oxidation states is reported [127] to reduce around 10 % the methanol uptake, particularly the oxidized state, along with a very small reduction of the water uptake. A similar study on Nafion/polyaniline membrane reported a larger reduction (40 %) of the methanol uptake, which reached 50 % when Si02 was added to the composite membrane, without any significant effect on the water uptake [125]. 

E.A., Ocampo, A.L., Espinosa-Medina, M.A. and Sebastian, P.J. 2003. A modified Nafion membrane with in situ polymerized polypyrrole for the direct methanol fuel cell. LPower Soj. 124 59-64. 

Other polymer systems that have been studied with the electrochemical quartz crystal microbalance are poly(tetracycaoquinyldimethane) [91], poly(3-methylthiophene) [92], diheptylviologen bromide [93], polyani-line/Nafion composite films [94] and polypyrrole/3-(pyrrol-l-yl) propane sulphonate composites [95], and poly(pyrrole) composites with several anions [96-97]. 

Saito Y, Ogawa A, Uchida S, Kubo T, Segawa H (2010) Energy-storable dye-sensitized solar cells with interdigitated nafion/polypyrrole-Pt comb-like electrodes. Chem Lett 39 488 89... 

Polypyrrole cells using Li/LiC104 in PC as electrolyte have been proposed and extensively investigated [410-12]. Commercial application has been achieved two large companies have produced batteries based on litium/polypyrrole [413]. Recently a polypyrrole/Nafion composite was used in a lithium/poly(ethylenoxide) cell with improved characteristics over the simple polypyrrole electrode [414]. 

Nafion membranes were modified by the in situ electrodeposition of polypyrrole inside the membrane pores on the anode side only, in order to prevent the crossover of methanol in the direct methanol fnel cell (DMFC) [86]. The modified membranes were studied in terms of morphology, electrochemical characteristics, and methanol permeability. FTIR and SEM confirmed the presence of the polypyrrole on the anode side of the Nafion membrane. SEM showed the polymer to be present both on the membrane surface and inside the membrane pores. It was found to be deposited as small grains, with two distinct sizes the smallest particles had a diameter of around 100 nm, whereas the larger particles had diameters of around 700 ran. Methanol permeability was determined electrochemically and was shown to be effectively reduced. Controlling the phase through blend or block co-polymer will be a good approach in PEM development for satisfying requirement in various DMFC systems. 

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