Poly (ethylene terephthalate) (PET)와 Poly (1, 4-phenylene terephthalate) (PHT) 의 copolyester (PEHT)를 PHT반복단위의 함량이 30 mol% 미만인 범위에서 용액중합으로 합성하고 이들의 물성을 조사하였다. PEHT 중 PHT의 함량이 증가함에 따라 유리전이 온도, 결정화 속도, 내열성은 증가하고, 녹는점은 감소하였다. PHT 반복단위 함량이 16.5, 24.9 mol %인 경우 액정성을 관찰할 수 있었으며, PET 반복단위와 PHT 반복단위에 의한 결정이 혼재함을 광각 X-선 회절로부터 관찰하였다.

Copolyesters (PEHT) of poly (ethylene terephthalate) (PET) and poly (1, 4-phenylene terephthalate)(PHT) were synthesized by the solution polymerization with the PHT unit contents of less than 30 mol %, and their physical properties were studied. As the content of PHT unit in PEHT was increased, glass transition temperature, crystallization rate, thermal stability increased, whereas melting temperature decreased. When the PHT unit contents were 16.5 and 24.9 mol %, nematic mesophase was observed. Wide angle X-ray diffraction pattern showed the peaks originated from both PET unit and PHT unit.