CONTRIBUTIONS FROM INTERFACIAL POLARIZATION, CONDUCTIVITY AND POLYMERRELAXATIONS TO THE COMPLEX PERMITTIVITY OF A FILM OF POLY[(5-ETHYL-1,3-DIOXAN-5-YL)METHYL ACRYLATE] CONTAINING IONIC IMPURITIES

The complex permittivity of a him of the polymer poly[(5-ethyl-1,3-dio xan-5-yl)methyl acrylate] of width 0.4 mm and containing very small am ounts of ionic impurities has been studied at a range of frequencies f rom 0.01 Hz to 100 kHz and at a range of temperatures from -135 to + 1 40 degrees C. Some mechanical determinations of the complex Young modu lus have also been performed for the same polymer. To separate the sur face polarisation effects and the conductivity effects from the dielec tric relaxations of the polymer chains and side-chains we have used th e same theoretical methods as earlier described for a film of a copoly mer of vinylidene cyanide and vinyl acetate and for a film of oly[4-(a cryloxy)phenyl-(4-chlorophenyl)methanone]. The diffusion coefficient o f the most rapidly diffusing ion is studied as a function of temperatu re. The diffusion coefficient follows a non-Arrhenius Vogel relation w ith the same Vogel temperature as the alpha-relaxation (glass-rubber). Both phenomena may be interpreted using the Cohen-Turnbull theory of free volume as has previously been done for the diffusion of oxygen th rough poly(cyclohexyl acrylate). The fractional free volume at the gla ss transition temperature (ca. 36 degrees C) is found to be 0.031, clo se to the range normally found (0.025 +/- 0.005). A beta-relaxation is also found at higher frequencies and lower temperatures. This relaxat ion shows Arrhenius behaviour with an activation energy E-double dagge r/R = 5780 K. The alpha- and beta-relaxations seem to merge at ca. 100 degrees C and in addition a relaxation more slow than the a-relaxatio n is found at even higher temperatures. This relaxation can only be se en after correction of the dielectric loss for conductivity. The mean activation energy of this relaxation in the temperature range 90-140 d egrees C is practically identical with the mean activation energy of t he alpha-relaxation in the same range of temperatures (E-double dagger /R approximate to 15 000 K). The slow relaxation is probably connected with the motion of the polymer molecule as a whole in the 'virtual tu bes' of long-range, topological entanglements, for example by 'reptati on'. At very high frequencies (50-100 kHz), isochronous graphs of diel ectric loss vs. temperature exhibit a splitting of the or-peak into tw o peaks.