Abstract
The dielectric behavior of a family of block copolymers based on poly(butylene terephthalate) (PBT) and aliphatic polycarbonate (PC), with the composition of PBT varying from 100 wt.-% to 40 wt.-%, has been investigated by broad-band dielectric spectroscopy in the frequency range from 10–1 to 109 Hz. At temperatures above the glass transition, the merging of local γ process and the cooperative β process was studied for PBT and 40/60 and 60/40 PBT-PC copolymers. The experimental data can be satisfactorily analyzed considering a sum of two Havriliak-Negami functions indicating that both β and γ relaxations can be treated as independent processes. Dielectric measurements for the 40/60 copolymer were extended over and above the melting region to characterize the influence of crystal melting on the dynamic behavior. It is shown that the progressive loss of the crystalline lamellar stack microstructure, as characterized by differential scanning calorimetry and small- and wide-angle X-ray scattering, provokes a dramatic change in the dynamic behavior of both the β and γ process.
Published Version
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