Acetylated 4,4’-biphenydiol (ABD) and biphenyl-4,4’-dicarboxylic acid (BDCA) were polycondensed in inert aromatic reaction media at various temperatures and monomer concentrations. At temperatures less than or equal to 300 degrees C oligoesters were obtained, which according to infra-red and C-13 nuclear magnetic resonance cross-polarization/magic-angle spinning spectroscopic characterization preferentially possess two carboxyl end-groups. Furthermore, polycondensations were conducted at 400 degrees C whereby high-molecular-weight polyesters were obtained. Electron microscopy revealed the formation of lengthy crystallites, but true needle-like whiskers were never formed. Analogous polycondensations were conducted with acetylated hydroquinone and BDCA or with ABD in combination with terephthalic acid. Furthermore, all three polyesters were prepared by polycondensation of the free diphenols with terephthaloyl chloride or biphenyl-4,4’-dicarboxylic acid dichloride in Marlotherm-S at 400 degrees C. Highly crystalline polyesters were obtained whenever the polycondensations were conducted at 400 degrees C in Marlotherm-S, but in all cases the morphology was that of irregular particles. Wide-angle X-ray diffraction powder patterns measured with synchrotron radiation up to 440 degrees C revealed that all three polyesters undergo a gradual transition from an orthorhombic crystal lattice to pseudo-hexagonal and finally to hexagonal chain packing with increasing temperature. These transitions cover a temperature range of more than 400 degrees C. Only in the case of the polyester derived from hydroquinone and BDCA was a reversible first-order phase transition observed around 506 degrees C.