Small amounts of dimethyl-4,4'-biphenyldicarboxylate, 2,7-dimethyl-4,5,9,10-tetrahydropyrenedicarboxylate, and dimethyl-2,7-pyrenedicarboxylate have been copolymerized into poly(ethylene) terephthalate (PET). The thermal transitions of the copolymers have been characterized, and the crystallization rates have been measured isothermally. Avrami analysis indicates that all the copolymers crystallized at a slower rate than that of the PET homopolymer. Addition of perylene to the copolymers containing pyrene enhanced the rate of crystallization, which could be the consequence of stacked arene assemblies serving as templates for crystal formation.