Dielectric relaxation of the alternating terpolymers of ethylene, propylene, and carbon monoxide

The alternating terpolymers of ethylene, propylene, and carbon monoxide were characterized by wide-angle x-ray scattering (WAXS), differential scanning calorimeter (DSC), thermally stimulated depolarization currents, and dielectric relaxation spectroscopy (DRS). At room temperature, the terpolymers were x-ray amorphous; however, the existence of weak endothermal effects over fairly broad temperature intervals above the glass transition suggested that they should be classified as "microcrystalline" (in a sense that the ultimate level of crystallinity lies beyond the resolution limits of ordinary WAXS instruments). The DRS data in the temperature intervals of α- and sub-glass relaxations were fitted quantitatively to the Havriliak-Negami equation. The characteristic parameters for the α-relaxation were consistent with classification of terpolymers as relatively fragile glass formers; however, their high fragility was attributed to steric constraints to the motion of chain dipoles by the residual network of microcrystals. Strong asymmetry of the dielectric subglass relaxation was regarded as additional experimental evidence for the interference of the spatial network of microcrystallites with the motion (in this case, noncooperative) of chain segments.