Phase transition process of polyester from phenanthrene, poly(oxyheptamethyleneoxy-2,7-phenantrenedicarbonyl), a main chain
type liquid crystalline polymer, was investigated by simultaneous DSC-XRD measurements using the synchrotron radiation facility
(PF). Three exothermic DSC peaks were observed during cooling from the isotropic liquid state. These DSC peaks were assigned
to the transition from the isotropic liquid to the smectic A, that from the smectic A to C, and that from the smectic C to
the crystalline state, respectively, as determined by XRD profiles. The rate of transition from the smectic A to C was very
slow compared with the liquid crystalline transition and the crystallization. From the DSC-XRD results, the thermal expansion
along c-axis in the crystal and smectic phases are 4.110−4 and 1.410−3 nm K−1 , respectively.