Synthesis and characterization of a homologous series of aromatic-aliphatic polyesters with non-coplanar 2,2′-dimethylbiphenylene units

Abstract

We report on the synthesis and characterization of a series of semiflexible polyesters containing a non-coplanar biphenylene unit and a flexible alkylene spacer of variable length. The number of methylene groups in the spacer was varied from three to eight. The polyesters were synthesized by interfacial polycondensation. The polymer properties were characterized by thermal analysis, optical microscopy and wide-angle X-ray diffraction. Melting transitions and glass transition temperatures show a strong odd-even effect with respect to the number of methylene groups in the flexible spacer. The crystallinity is reduced by the incorporation of the 2,2′-dimethylbiphenylene unit. In the polyesters with an odd number of methylene groups the crystallization is suppressed and indications of a crystalline phase were only observable after extensive annealing.