Miscibility in blends of liquid crystalline copolyester and semicrystalline poly(ethylene-2,6-naphthalene dicarboxylate)

The miscibility in blends of random liquid crystalline copoly(oxybenzoate-e thylene terephthalate) at a molar ratio of 60:40 (P64) and semicrystalline poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) were investigated with d ifferential scanning calorimetry, wide angle X-ray diffraction and polarize d optical micrography. It was found that P64 and PEN were partially miscibl e as evidenced from the appearance of a single glass transition temperature for each blend at different compositions. Furthermore, the Flory-Huggins i nteraction parameter, chi(12), for P64 and PEN was determined to be -1.13 t hrough the melting point depression analysis, indicating miscibility in ble nds of P64; and PEN at the melt state. The coherence lengths of PEN in the presence of a small amount of P64, around 3%, were larger than that in pure PEN, implying the regularity of PEN crystals in the blends with low P64 co ntent being more perfect than that of the pure PEN. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.