FINE-STRUCTURES OF COPOLYESTERS CONTAINING NAPHTHALENE AND 9,10-DIHYDROPHENANTHRENE RINGS

Copolyesters composed of poly(ethylene 2,6-naphthalate) and poly(ethyl ene 9,10-dihydrophenanthrate) (PEN/PEHP copolymers) with different cop olymer compositions were synthesized and their thermal properties and fine structures were investigated using thermal analysis and X-ray dif fraction methods. T(g)s Of the copolymers increased with increasing mo lar fraction of the PEHP component; on the other hand, their T(m)s dec reased slightly and their crystallinity also decreased. The crystallit es in the copolymers were assigned to the alpha- or beta-polymorphic f orms of PEN. In particular, annealed samples containing 5% and 10% PEH P exhibited X-ray diffraction patterns showing the coexistence of the alpha- and beta-forms. In the case of samples containing 20% PEHP the crystallites were of the beta-form. Thus, the crystalites formed in th e copolymers are composed of PEN sequences, while PEHP sequences remai n in the amorphous regions. PEHP sequences interfere with the crystall ization of PEN/PEHP copolymers and have a strong influence on the chai n packing mode of the unit cell in the copolymers. (C) 1997 Elsevier S cience Ltd.