Poly(ethylene terephthalate), PET, poly(ethylene-2, 6-naphthalate), PEN, and poly(ethylene terephthalate-co-naphthalate), PET/PEN copolymer were synthesized by two-stage esterification and polycondensation reaction. These polymers were characterized in their copolymer composition by IR and 1H-NMR, molecular weight and molecular weight distribution by viscometry and GPC. From the characterization results, PET/PEN copolymer synthesized from BHET/BHEN oligomer showed nearly the same copolymer composition as feed ratio by 1H-NMR analysis. From the GPC and inherent viscosity data, it was found that copolymer have molecular weight Mn between 15,000 and 26,000g/mo1. The destruction of crystallinity occured rapidly in PET/PEN copolymers with PET content of above 5mol % and the copolymer which has PET content above 20mo1% did not show crystallinity by DSC measurement with 5℃/min heating rate. Glass transition temperature of PET/PEN copolymer followed Fox's equation. Copolymers sample containing about 5mol% PET (PEN-95) showed slightly higher degree of crystallinity and rate of crystallization than PEN homopolymer. From the isothermal crystallization experiment at 210℃, the Avrami exponent of PET was determined to be 2.76, and those of PEN and PEN-95 were close to 2.

Poly(ethylene terephthalate), PET, poly(ethylene-2, 6-naphthalate), PEN, 그리고 poly(ethylene terephthalate-co-naphthalate), PET/PEN 공중합체를 에스테르 교환 반응과 중축합 반응의 두단계 반응으로 합성하였으며, 이 중합체들의 분자량과 분자량 분포는 점도법과 GPC, 공중합체의 조성은 IR과 NMR로 조사하였다. 분석결과, 1H-NMR에 의한 공중합체내의 조성비와 공단량체 공급비가 거의 일치하는 것을 볼 수 있었으며, GPC 측정으로부터, 공중합체들이 Mn=15,000에서 26,000g/mo1 사이의 분자량을 가짐을 확인하였다 DSC 분석결과, PET 함량이 5mol%이상이 되면 PET/PEN 공중합체의 결정성 과괴가 급속히 일어났으며, PET 함량이 20mo1%이상에서는 승온속도를 5℃/min로 낮추었을 때도 DSC 측정시 결정화가 관찰되지 않았다. 그리고 PET/PEN 공중합체의 유리 전이 온도의 변화는 Fox's equation을 따랐다. 또한, PET 함량이 약 5mol% 포함된 공중합체의 결정화 속도와 결정화도는 PEN 단일중합체와 비교해서 급격한 증가를 보였다. 210℃에서의 등온 결정화 거동에서, PET의 Avrami 지수는 2.76이었고, PEN과 PEN-95는 2에 가까운 값을 가졌다.

Keywords: poly(ethylene terephthalate-co-naphthalate); synthesis; crystallization behavior