Partially fluorinated electrical

As part of an effort to develop high-performance, high-temperature-resistant polymers for microelectronics applications, we also recently described a series of both partially fluorinated and nonfluorinated poly(aryl ether ketone)s containing amide, amide-imide, cyano oxadizole, or pyridazine groups and characterized their thermal and electrical properties.11... 

Table 14.5 lists the thermal, electrical, and optical properties of perfluorinated polyimides, along with those of partially fluorinated and unfluorinated polyimides. Because of die flexible structure of the lOFEDA component, the polymer decomposition temperatures and values of perfluorinated polyimides are slightly lower than those of conventional polyimides. This coincides with the results of Hougham et al. who reported that an increase in fluorine content in... 

Table 14.5. Thermal, Electrical, and Optical Properties of Perfluorinated, Partially Fluorinated, and Unfluorinated Polyimides...

PFA and MFA exhibit considerably better electrical properties than most traditional plastics. In comparison with the partially fluorinated polymers, they are only slightly affected by temperature up to their maximum service temperature.54... 

The enhancement of both energy density and cell safety of rechargeable lith-ium(-ion) batteries is important for electric vehicle and power grid applications. Therefore, partially fluorinated organic compounds are expected as a good solvent... 

Perfluorocyclobutane (PFCB) polyaryl ethers are one such class of partially fluorinated polymers which combine the processability and durability of engineering thermoplastics with the optical, electrical, thermal, and chemical resistant properties of traditional fluoroplastics. Developed originally at The Dow Chemical Company" in Freeport, TX, PFCB polymers are prepared by the radical mediated thermal cyclopolymerization of trifluorovinyl ethers (Figure 1) and have, to date, provided a variety of thermoplastic and thermosetting materials possessing a tunable range of... 

Fig. 12 Partially fluorinated silylethynyl-functionalized anthradithiophenes (left). Single crystal of TES-ADT-F2 and its electrical characteristics (right) - reproduced with permission of the American Chemical Society from [53]...

Those critical functions of membrane for DMFC are simple but most important. Required functions are ionic conductivity, electrical insulation, gas and liquid (especially methanol) tightness, and chemical and mechanical stability. As indicated in Fig. 13.2, ohmic polarization is mainly due to the ionic resistance of membranes, but the low open circuit potential of cathode is also mainly coming from the voltage drop by mixed potential made of fuel crossover through the membrane. The low cost of material and process is also another factor in terms of commercialization. Especially for mobile applications, membranes have the additional function for mass balance of liquid fuel and water products circulated out of or through the membrane. In this manner, alternative membranes are under development and researchers are focused on four types perfluorinated and partially fluorinated membranes hydrocarbon and composite and other ionomer modifications inorganic materials. The current state of the art and technical approaches to these materials are discussed in detail elsewhere in this volume. 

For CFi this amount of double-bond character (19 percent), with the amount of partial ionic character of the C—F single bond (43 percent) corresponds to the electric charge +0.96 on the carbon atom Hence we may say that this molecule contains a C+ atom, with one negative charge resonating among the four fluorine atoms. As a first approximation the structure may be described as a resonance hybrid of the 12 structures of type A ... 

Fig. 12. Relationship between electrical conductivity and partial pressure of oxygen (reproduced with permission from J. Fluorine Chem., 87 (1998) 229 [39]).

There is yet another phenomenon that points to a 1,4-addition of fluorine atoms occurring at least partially The products obtained from the reaction of single-walled carbon nanotubes with fluorine are definite nonconductors (resistance >20 MQ), while the nanotubes employed feature a resistance of 10-15 2 only. Considering the structures that result from a consecutive 1,2- or 1,4-addition of fluorine, respectively, reveals that an electric current via conjugated it-bonds would still be possible in the 1,2-adduct (Figure 3.70). In the 1,4-adduct, on the other... 

---