Thermotropic polyesters. 2: Synthesis, characterization and thermal transitions of copolyesters containing 4,4′-bis (ω-alkyloxy) biphenyl isophthalate units

Thermotropic copolyesters containing an isophthalate unit and mesogenic 4, 4′-bis (ω-hydroxyalkyloxy) biphenyls (n = 3, 4, 6) with different numbers of methylene units have been synthesized by melt polymerization. The number-average molar mass (M_n) was estimated from end group analysis by ¹H NMR. The copolymer compositions were also obtained from ¹H NMR. The thermal behavior of the copolymers containing even-even (n = 4, 6) and odd-even (n = 3, 4) pairings has been investigated and is also compared with that of the analogous homopolymers. The copolymers exhibit reduced melting point and extending liquid crystalline range identified using polarizing microscopy and DSC. All of the obtained compounds were characterized by conventional spectroscopic methods.