Dielectric relaxations in thermotropic liquid crystalline polypeptides

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 α´₁ 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 and α₂ peaks 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