Phase transitions of liquid crystalline polyesters: Poly(heptane-1,7-diyl-4,4′-biphenyldicarboxylate)

Abstract

Wide-angle X-ray scattering was applied to investigate the non-isothermal and isothermal phase transitions of poly(heptane-1,7-dyil-4,4′-biphenyldicarboxylate). It is suggested that the isotropic–smectic (I–S) transition is controled by a nanophase separation with a critical point Tns=151 °C. Nanophase separation is followed by a first-order S–Cr (crystal) transition. At isothermal conditions above Tns only S phase exists, whereas below it the S phase appears first and the Cr phase grows from the S by nucleation and three-dimensional crystal growth.