Abstract
PET oligomers with different degrees of polymerization containing PHB as end groups were synthesized by melt condensation of bis(2-hydroxyethyl) terephthalate (BHET) in the presence of ethylp-hydroxybenzoate (EtPHB). Coupling the oligomers with terephthaloyl chloride, a series of block copolymers with identical triad aromatic ester “hard” segments as mesogen and different lengths of PET “soft” segments as spacer were obtained. Observation with a cross-polarized optical microscope shows that these copolymers are thermotropic in a certain range of the spacer length (n). Asn increases, the melting point (Tm) of the copolymer also increases, following the increasing molecular weight. The isotropic transition temperature (Ti) and the LC phase range (ΔT), on the other hand, decrease with the increasingn. Whenn exceeds a critical value, the LC phase disappears.
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