Bipolar polymers

Research Focus Development of bipolar polymer electrolytes, which are thermally and hydrolytically stable, flexible, and exhibit low methanol permeability and high proton conductivity. 

Wodzki R and Nowaczyk J. Membrane transport of organics. III. Permeation of some carboxyUc acids through bipolar polymer membrane. J Appl Polym Sci, 2001 80(14) 2705-2717. 

FIGURE 23.2 Bipolar polymer electrolyte electrolysis cell connected in series to enlarge the applied potential. The cathode, anode, current collectors, polymer electrolyte, and electrocatalyst with the evolution of gases are shown. 

Figure 5.11 Synthesis of block copolymer-grafted MWCNTs (top), and the representative TEM image of PHEMA-Z -PMMA-grafted MWCNT. The insert shows the cartoon of the bipolar polymer layer-coated CNT. Reprinted with permission from Kong et...

Figure 16.17 Typical output characteristics of the bipolar polymer blend FETs in (a) electron enhanced mode and (b) hole enhancement mode. (Reprinted with permission from Ref. [15]).

One idea to realize a pin junction with conjugated polymers is to create it in situ by electrochemical doping. By using the conjugated polymer in a solid slate electrochemical cell, the production of bipolar light-emitting pin junction devices can be realized [69, 70]. 

Both share more or less the same merits but also the same disadvantages. The beneficial properties are high OCV (2.12 and 1.85 V respectively) flexibility in design (because the active chemicals are mainly stored in tanks outside the (usually bipolar) cell stack) no problems with zinc deposition in the charging cycle because it works under nearly ideal conditions (perfect mass transport by electrolyte convection, carbon substrates [52]) self-discharge by chemical attack of the acid on the deposited zinc may be ignored because the stack runs dry in the standby mode and use of relatively cheap construction materials (polymers) and reactants. 

Composite structures that consist of carbon particles and a polymer or plastic material are useful for bipolar separators or electrode substrates in aqueous batteries. These structures must be impermeable to the electrolyte and electrochemical reactants or products. Furthermore, they must have acceptable electronic conductivity and mechanical properties. The physicochemical properties of carbon blacks, which are commonly used, have a major effect on the desirable properties of the conductive composite structures. Physicochemical properties such as the surface... 

Furan was dimethoxylated to give 2,5-dihydro-2,5-dimethoxyfuran, using electrogenerated bromine molecules generated from bromide salts in electrolyte solutions [71]. This reaction was characterized in classical electrochemical reactors such as pump cells, packed bipolar cells and solid polymer electrolyte cells. In the last type of reactor, no bromide salt or electrolyte was used rather, the furan was oxidized directly at the anode. H owever, high consumption of the order of 5-9 kWh kg (at 8-20 V cell voltage) was needed to reach a current efficiency of 75%. 

Ma and coworkers [154] synthesized a bipolar luminescent PPV-based polymer 111, which contained both donor triarylamine and acceptor oxadiazole moieties in the backbone. A device fabricated with this polymer (ITO/PEDOT/111/CsF/Al) showed a maximum brightness of 3600 cd/m2 and a maximum luminescent efficiency of 0.65 cd/A (< el = 0.3%), about 15 times brighter and more efficient than the device of the same configuration with a nonoxadiazole polymer 112. 

Z. Peng, Z. Bao, and M.E. Galvin, Polymers with bipolar carrier transport abilities for light emitting diodes, Chem. Mater., 10 2086-2090, 1998. 

Typical host materials can be summarized as electron transport hosts, hole transport hosts, bipolar hosts, large band-gap hosts for blue or white emission, or polymer hosts. 

There has been an accelerated interest in polymer electrolyte fuel cells within the last few years, which has led to improvements in both cost and performance. Development has reached the point where motive power applications appear achievable at an acceptable cost for commercial markets. Noticeable accomplishments in the technology, which have been published, have been made at Ballard Power Systems. PEFC operation at ambient pressure has been validated for over 25,000 hours with a six-cell stack without forced air flow, humidification, or active cooling (17). Complete fuel cell systems have been demonstrated for a number of transportation applications including public transit buses and passenger automobiles. Recent development has focused on cost reduction and high volume manufacture for the catalyst, membranes, and bipolar plates. 

Figure 4.1 shows a schematic of a typical polymer electrolyte membrane fuel cell (PEMFC). A typical membrane electrode assembly (MEA) consists of a proton exchange membrane that is in contact with a cathode catalyst layer (CL) on one side and an anode CL on the other side they are sandwiched together between two diffusion layers (DLs). These layers are usually treated (coated) with a hydrophobic agent such as polytetrafluoroethylene (PTFE) in order to improve the water removal within the DL and the fuel cell. It is also common to have a catalyst-backing layer or microporous layer (MPL) between the CL and DL. Usually, bipolar plates with flow field (FF) channels are located on each side of the MFA in order to transport reactants to the... 

Injection molded thermoplastic bipolar plates made of Vectra LCP (liquid crystal polymer) and Fortron PPS fabricated by Ticona Engineering Polymers, (http //www.ticona.com/redesign/ index/markets/innovation/fuel cell.htm Ticona Engineering Polymers. 2008 accessed March 2008.)... 

Cho, E. A., U. S. Jeon, H. Y. Ha, et al. 2004. Gharacteristics of composite bipolar plate for polymer electrolyte membrane fuel cells. Journal of Power Sources 125 178-182. 

Wang, H., and J. A. Turner. 2004. Investigation of a duplex stainless steel as polymer electrolyte membrane fuel cell bipolar plate material. Journal of Power Sources. 128 193-200. 

The electrolyte is a perfluorosulfonic acid ionomer, commercially available under the trade name of Nafion . It is in the form of a membrane about 0.17 mm (0.007 in) thick, and the electrodes are bonded directly onto the surface. The electrodes contain very finely divided platinum or platinum alloys supported on carbon powder or fibers. The bipolar plates are made of graphite-filled polymer or metal. 

In addition to water and inorganic solids (salts dissolved in cell fluids, shells, and bones), organisms consist of a mix of organic substances. Some of these are macromolecules (e.g., globular proteins, cellulose). Some combine to form subcellular and tissue structures built with combinations of lipids, proteins, carbohydrates, and some specialized polymers like cutin or lignin (Fig. 10.2). These diverse organic materials cause organisms to have diverse macromolecular, cellular, and tissue portions that may be apolar, monopolar, and/or bipolar. 

A more recent LPB development in Israel involves the fabrication of bipolar cells using a composite polymer electrolyte (CPE), and a pyrite-based positive... 

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