SYNTHESIS AND CHARACTERIZATION OF A HOMOLOGOUS SERIES OF AROMATIC-ALIPHATIC POLYESTERS WITH NONCOPLANAR 2,2'-DIMETHYLBIPHENYLENE UNITS

We report on the synthesis and characterization of a series of semifle xible polyesters containing a non-coplanar biphenylene unit and a flex ible alkylene spacer of variable length. The number of methylene group s in the spacer was varied from three to eight. The polyesters were sy nthesized by interfacial polycondensation. The polymer properties were characterized by thermal analysis, optical microscopy and wide-angle X-ray diffraction. Melting transitions and glass transition temperatur es show a strong odd-even effect with respect to the number of methyle ne 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 suppress ed and indications of a crystalline phase were only observable after e xtensive annealing.