ABSTRACT:Dielectric relaxation of poly(tetrafluoroethylene-co-perfluorovinyl ether) (PF A) grafted by ethyl methacrylate (EMA) and vinyl acetate (V Ac) of different compositions prepared by direct radiation was studied at O.l, 1, 10, and 100kHz between 273 and 550 K. Two well resolved relaxation peaks are observed in all films except that with EMA/V Ac of compositon 10j90wt% in which the second peak is masked. In PFA film grafted by EMA/VAc of 50/50 wt% at low temperature the third relaxation was observed. The activation energy for the relaxation was determined from Arrhenius plots. The ac conductivity of the films was investigated and the activation energy of conduction was evaluated. X-Ray diffraction patterns and IR spectra were also measured.KEY WORDS Dielectric Constant s' j Dielectric Loss s" j Conductivity j Activation Energy j Measurement of dielectric loss (s") and relative permittivity as functions of frequency and temperature is a well established method of detecting molecular motion in macromolecules, particularly in the solid state. Amorphous polymers may exhibit five types of relaxation regions 2 : (1) motion of the entire chain as a unit; (2) motion of a chain segment of perhaps 50-100 carbon atoms, i.e., glass transition; (3) motion of a 2, 3, or 4 carbon atom moiety about the chain axis; (4) motion of a side group about an axis at right angles to the chain, and (5) very low temperature loss which may or may not be the same as (4). Not all relaxation processes are observed in dielectric experiment. A process is dielectrically active only if it involves the reorientation of the dipole-moment vector. 3 The dielectric properties of flexible polar side-amorphous polymers depend on the position and direction of the dipolar group with respect to the chain backbone. Two main kinds of relaxation are generally observed in this type of polymer. A high temperature relaxation (I)() associated with chain backbone motion and a low temperature relaxation (p) which results from the side group motion. 4 • 5 Even in amorphous polymers without side groups, such as amorphous polyesters, 6 two kinds of relaxation are also observed. The molecular mechanism of the hightemperature relaxation is also the large-scale conformational rearrangement of the main chains; the low-temperature relaxation is due to the local twisting modes of main chains when the large-scale conformational rearrangement of main chain is frozen. 7 -9 This is also called P relaxation since it has characteristics similar to the p relaxation in polymers with flexible polar side groups, both originate in local motions. 10 Relaxation of methacrylate polymers has been the object of many studiesY - 13 The dielectric behaviour of poly(vinyl ester) is of particular interest to many authors. 15 -17 In poly(vinyl acetate) (PVAc) two relaxation regions, (I)() and (p), are observed. 14 • 15 In this study, the dielectric relaxation of poly(tetrafluoroethylene-coperfluorovinyl ether) (PF A) film grafted with different compositions of ethyl methacrylate and vin...
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