Microwave frequencies poly

The piezoelectric phenomena have been used to generate ultrasonic waves up to microwave frequencies using thin poly(vinylidene fluoride) transducers. In the audio range a new type of loudspeaker has been introduced using the transverse piezolectric effect on a mechanically biased membrane. This development has been of considerable interest to telephone engineers and scientists. 

Temperature dependent microwave frequency dielectric constant of poly(aniline)-camphor sulfonic acid (PAN-CSA) prepared in CHCI3 and m-cresol. Inset microwave frequency conductivity of PAN-CSA (m-cresol). Data were recorded at 6.5 X 10 . After Reference [482], reproduced with permission. 

The direct absorption of moderate to low frequency, nonionizing, electromagnetic radiation - microwaves - by DNA polymer molecules is a potential source of biological effects. As an introductory study of this question, we have evaluated the absorption of isolated homopolymer straight chains of poly dG-poly dC. For some absorption processes we have also investigated some effects of a surrounding aqueous medium. 

Smart skins are to be considered in the context of radar absorbing materials where solutions have been given in [113,114]. Smart microwave windows have been proposed in the context of using poly(aniline)-silver-polymer electrolyte composite materials which have shown a change in microwave reflectivity when a small electrical dc potential is applied among them [115]. An adaptive radar absorbing structure based on the topology of a Salisbury screen combined with an active frequency selective surface controlled by PIN diodes has been described in [116] which allows for superior reflectivity-bandwidth. 

For example, blends and semi-IPN of polypyrrole and EPDM rubber, prepared by calendering, absorb 85% of microwave radiation in the 10-13 GHz range [167]. Surface deposition of polypyrrole onto poly-(vinylchloride) produced composites with microwave absorption properties in the 0.1-20 GHz frequency range [168]. The same authors also studied the shielding characteristics of blends of polyaniline and poly(3-octylthiophene) with polystyrene and with the copolymer of ethylene and vinyl acetate. For defense purposes, however, a larger frequency range should be covered, but this only encourages continuation of the research. 

Most work to date has concentrated on a particular aspect of microwave properties, e.g. conductivity or dielectric constant, with few studies of the complete spectrum of properties over broad frequency ranges. For example. Fig. 12-2a.b show the DC vs. microwave (6.5 GHz) conductivity and the microwave (6.5 GHz) dielectric constant vs. temperature for a series of poly(anilines) measured by Javadi et al. [195]. The behavior observed- microwave conductivity greatly exceeding DC conductivity for higher doping levels, and dielectric constant being independent of temperature for low doping levels- is typical of CPs. Buckley and Eashoo [430] obtained relatively poor values for e and e", ca. 90 and 60 (at the Ka band, ca. 33 GHz) for compacted P(Py)/Cl powder. 

Naishadham [475] used the cavity perturbation technique to study the overall microwave characteristics, including EMI-SE, of the CPs poly(acetylene) (P(Ac)) and poly(p-phenylene-benzobisthiazole) (P(BT)), at 8.9 and 9.89 GHz, and continuously in the 2-20 GHz frequency region. Figs. 19-la.b.c summarize some of his results. 

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