Effect of thermal history and rigid unit on rheological properties of the thermotropic liquid crystalline polyesteramides

Abstract

The effects of thermal history and rigid units on rheological properties of thermotropic liquid crystalline (TLC) polyesteramides with bulky side group were studied by differential scanning calorimetry (DSC) and static and dynamic viscoelastic measurements. Rheological properties of TLC polyesteramides were largely dependent on the amount of the rigid unit as well as the annealing condition. The effect of thermal history on dynamic moduli was investigated above and below the transition temperature of metastable equilibrium state defined by Cheng. G' (dynamic storage modulus) and G " (dynamic loss modulus) of TLC polyesteramides measured above the transition temperature (280 degrees C) were little affected by the amount of the rigid unit and the thermal history, whereas below the transition temperature (220 degrees C) both were largely dependent on the thermal history. These dependencies were also confirmed satisfactorily by the DSC measurement. The copolyesteramide (X = 0.7) showed viscoelastic behavior with a longer relaxation time in the molten state than the homopolyesteramide( X = 1.0), because the nematic mesophase became more prominent as the amount of rigid unit increased.