Various poly(p-phenylene alkylene dicarboxylates) (PPADs) were synthesized and their crystallization behavior was examined as functions of the length and the odd/even numbers of carbon atoms in the aliphatic component. PPADs with longer aliphatic units of even-numbered carbon atoms were found to crystallize faster than do those of other cases. The results are compared with the crystallization behavior of conventional poly( alkylene terephthalate)s(PATs), e.g., poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PET), which have the same chemical composition as the corresponding PPAD but the reversed direction of the ester group. The effects of this structural difference on the melting temperature and the crystallization kinetics are also discussed.