Blends with polypyrrole

Common conductive polymers are poly acetylene, polyphenylene, poly-(phenylene sulfide), polypyrrole, and polyvinylcarba2ole (123) (see Electrically conductive polymers). A static-dissipative polymer based on a polyether copolymer has been aimounced (124). In general, electroconductive polymers have proven to be expensive and difficult to process. In most cases they are blended with another polymer to improve the processibiUty. Conductive polymers have met with limited commercial success. 

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... 

Composites can also be prepared by electropolymerization from solutions containing dissolved polymer 307). Since films of polypyrrole or polythiophene are normally porous, it seems most likely that the dissolved polymer is simply entrained in the pores. Similarly, composites have been prepared by polymerization of pyrrole in the presence of acrylic latex, giving blends with 10-30 % polypyrrole that are conducting yet processable 808). Presumably the polypyrrole is distributed throughout the latex particles. 

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

Poly thiophene, PTP, and polypyrrole, PPR, blends with PS and PC were prepared by Wang et al. [1990] by thiophene or pyrrole electrochemical polymerization using electrodes coated with PS or PC hlms. The thiophene or pyrrole diffuses into the fihn and polymerizes in-situ in the film. Threshold conductivity occurs at 18 wt% for both conducting polymers in PS. Lower levels exist for PTP (12 wt%) and PPR (7 wt%) in PC. Miscibility of PPR/PC is attributed to the lower threshold limit as phase separated blends would be expected to have higher values. Previous studies with polyacetylene/PS blends reported threshold conductivity at 16 wt% polyacetylene [Aldissi and Bishop, 1985]. 

Comparing an injected polypyrrole/PVC blend with a granular magnetic material tuned at the same frequency (Figure 8.36), we have measured the reflection coefficient on 2 mm thick samples, and observed a bandwidth of the same order of magnitude. But the surfacic mass of 2.6 kg/m obtained in the case of the blend, reaches 5 kg/m for the granular magnetic material. 

So, there has also been considerable interest in the use of conducting polymers, particularly polypyrrole (PPy), polythiophene, and polyaniline (PANl), in the form of thin films or blends with conventional polymers as sensors for airborne volatiles such as alcohols, ethers, halogens, ammonia (NH3), NO2, and warfare simulants... 

Wang H. L., Toppare L., and Fernandez J. E., Conducting polymer blends polythiophene and polypyrrole blends with polystyrene and poly (bisphenol A carbonate). 

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]. 

Films prepared in a similar manner with Hydrin C are those utilizing poly(N,N -dimethyl-2,2 -bipyrrole) [220], and polypyrrole [221]. Electrochromic films of Hydrin C and poly(o-methoxyaniline) have also been produced in which the aniline polymer is chemically polymerized in the presence of p-toluene sulfonic acid and blended with Hydrin C with the blend cast from solution [219]. Another example in which an electrochromic polymer was electrochemically polymerized in the presence of an insulating polymer is that of polypyrrole-polyjether urethane) or polypyrrole-poly(ethylene-co-vinyl alcohol) composite films [222]. Both films switched between a yellow reduced state to a bluish brown oxidized state, similar to polypyrrole. 

Polyaniline Blend Fibers Fabrics Coated with Polypyrrole and Polyaniline... 

Conductive polymer such as poly aniline (PANI), polypyrrole (PPy), poly (3,4-ethylenediox-)rthiophene) (PEDOT) as the conductive agent, most often blended with a common fiber forming polymer (PA, PES, etc.) in the extrasion. 

The mechanical mixture of oxidant and polymer is also an interesting method to incorporate the oxidant in the polymer matrix. Blends of polypyrrole and EPDM rubber (a terpolymer of ethylene, propylene and ethylidene norbomene) were obtained using an EPDM matrix impregnated with CUCI2 by calendering [31]. 

The oxidant can also be incorporated into the polymer matrix by dissolution with the insulating polymer in a common solvent, followed by solvent evaporation. This procedure was used to prepare blends of polypyrrole with poly(vinyl chloride) [32,33], and with poly(vinyl alcohol) [34]. 

Blends of polypyrrole and Teflon were also prepared by the chemical oxidation of pyrrole in an emulsion of Teflon containing the ferric / -toluene sulfonate salt [69]. Pyrrole was added to the ferric salt aqueous solution and mixed with the Teflon emulsion stabilized by Triton X-100. After stirring for 3 hours a finely dispersed blend was obtained. This emulsion was coagulated with ethanol. Conductivity was reported to reach 1 S cm with a percolation behavior. This method could be used for large-scale production of the blend. 

Poly(p-phenyleneterephthalamide) is soluble in dimethyl sulfoxide and is used to produce the well-known Aramid fibers. A blend of this material and polypyrrole in the form of film was prepared by the electrode coating method and using a / -toluenesulfonate salt as electrolyte [82]. A comparison of the mechanical properties of the blend with pure polypyrrole showed that the blend is a tougher material with a higher modulus and lower elongation at break. Treatment of the blend with HCl raises the conductivity but also increases hardness and toughness. 

As pointed out previously, poly(ethylene terephtha-late) is also largely used in the production of fibers, but this polymer has been blended with conductive polymers only in the form of films. In one study a poly(ethylene terephthalate) film was used as support for the preparation of a blend of poly(methyl methacrylate) and polypyrrole [90]. The poly(ethylene terephthalate) film coated with poly(methyl methacrylate) was immersed in pure pyrrole monomer and transferred to an aqueous FeCl3 solution. Surface conductivities in the range of 100 S cm were... 

Emulsion polymerization of pyrrole was also used to prepare blends of polypyrrole with a poly(alkyl methacrylate) [95]. A chloroform solution of a poly-(alkyl acrylate) and pyrrole was dispersed in an aqueous surfactant solution generating an emulsion. An aqueous solution of an oxidant was added to the emulsion with stirring, polymerizing pyrrole. The precipitated blend could be hot pressed in the form of films with conductivities of 6-7Scm . The curve for the variation of the conductivity of the blend with the oxidant/pyrrole ratio shows a maximum at a ratio of two with subsequent decrease. However, the yield increases to nearly 100% up to a ratio of four. The percolation threshold is approximately 10 wt% of pyrrole. The type and the concentration of the surfactant also affect the yield and conductivity. The mechanical properties of the blend depends on the number of carbons in the alkyl chain of the insulating polymer host. The strain at break of hot-pressed films increases and the stress at break decreases in the direction methyl, ethyl, butyl (Figure 18.3). This is an example where the mechanical properties of the conductive blend could be tailored according to the alkyl substituent in the poly(alkyl methacrylate) used in its preparation. 

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