The synthesis and properties of poly(ethylene terephthalate) (PET) copolymers containing four bisester diamide structural units are reported. Two of the bisester diamides consist of three para-substituted aromatic rings, and the other two consist of three meta-substituted aromatic rings. The copolymers have been characterized by nuclear magnetic resonance, differential scanning calorimetry, and dilute solution viscometry. Three of the copolymers can be compression-molded into amorphous films for oxygen barrier testing, and one of these three films can be oriented for additional barrier testing. The three amorphous films all have lower permeabilities than unoriented PET. However, this difference diminishes upon the orientation of the polymer films.
Copolymers of poly(ethylene terephthalate) (PET) containing 6-oxy-2-carboxyanthracene (OA) and 6-oxy-2-carboxynaphthalene (ON) structural units are prepared by reactive blending of acetoxyarenecarboxylic acid comonomers with PET. The new copolymers are characterized by 1 H and 13 C NMR, DSC, dilute solution viscometry, optical microscopy, and wide-angle X-ray diffraction and compared to poly(ethylene terephthalate-co-4-oxybenzoate), PET-co-OB. Whereas 40 mol % of the OB unit is required to induce liquid crystallinity in PET-co-OB, only 20 mol % of OA or 30 mol % of ON units are required. This is also in contrast to copolymers containing similar amounts of symmetrical arenedicarboxylate structural units which do not form liquid crystalline phases.
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