Poly(alkylene isophthalate)s were prepared by different methods, either in solution or in bulk. The SEC measurements were evaluated in such a way that all oligomers were included. In solution (monomer conc. 0.1-0.7 mol/L) large fractions of rings were formed and high dispersities (up to 12) were obtained, which disagree with theoretical predictions. Polycondensations in bulk did neither generate cyclics by "back-biting" nor by end-to-end cyclization, when the maximum temperature was limited to 210 degrees C. The dispersities of these perfectly linear polyesters were again higher than the theoretical values. Regardless of the synthetic method monomeric cycles were never observed. Furthermore, SEC measurements performed in tetrahydrofuran and in chloroform and SEC measurements performed in three different institutes were compared. Finally, SEC measurements of five samples were performed with universal calibration and a correction factor of 0.7160.02 was found for normal calibration with polystyrene. (C) 2015 Wiley Periodicals, Inc.