Small amounts of dimethyl-4,4Ј-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.
The effect of incorporating phthalate, 1,8-naphthalenedicarboxylate, and 1,8-anthracenedicarboxylate structural units on the crystallization rate of PET are evaluated by isothermal and dynamic calorimetry. Although all of the comonomers retard crystallization, the 1,8-naphthalene unit shows no concentration dependence between 2.5 and 10% incorporation, in contrast to the smaller phthalate and larger anthracene units. The greater rate at which the 1,8-naphthalene copolymer crystallizes, relative to that of the other copolymers, is consistent with the notion that the U-turn geometry induces chain folding and nucleates crystallization.
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