Dielectric Relaxations in Thermotropic Liquid Crystalline Polypeptides

Document Type

Article

Publication Date

1-1-1993

Abstract

Thermally stimulated depolarization current (TSDC) and thermally stimulated polarization current (TSPC) measurements and the differential scanning calorimetry (DSC) method have been used for the investigation of thermal transitions in thermotropic poly(γ-stearyl-α, L-glutamate). The β peak (−80°C and α1 and α1 peaks registered between −50°C and 25°C were attributed to movements of side chain dipoles. The α2 peak, observed ≈ 43°C, was indicative of the melting of paraffinic side chains. The activation energies were determined for β peaks (Ea = 0.2 eV) and α2 peaks (Ea = 0.4 to 0.7 eV) at different heating rates. A good correlation between heating rate and the square of the maximum peak temperature was found, showing that these peaks are of dipolar origin. The α1 and α2 peaks were strongly influenced by thermal treatments, The position of α2 was close to that determined by DSC. Depending on the thermal history of samples the paraffinic side chain segments melted and crystallized over a large temperature range suggesting the formation of crystallites with different dimensions. The TSDC curves were symmetrical, that is the currents measured with two electrometers mounted on each face of the sample are identical. © 1993 IEEE

Publication Source (Journal or Book title)

IEEE Transactions on Electrical Insulation

First Page

122

Last Page

127

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