Polycaprolactone (PCL)-poly(butylene terephthalate) (PET) block copolymers were effectively synthesized through the transesterification reaction of PCL and PET in the presence of 1,4-butane diol(BD) followed by the chain extention reaction with 4,4'-diphenylmethane diisocyanate(MDI). The modulus of PCL-PBT block copolymer decreased sharply after the melting of PCL block on heating. As the degree of transesterification reaction was increased, the modulus below the melting temperature was decreased due to the reduced crystallinity of PCL block. Whereas, through the transesterification reaction, the modulus above the melting temperature was increased by the fine dispersion of PET crystalline region which acts as a physical crosslinker. The shape memory effect of PCL-PBT block copolymer was increased as the content of PCL block was increased, and as the fine dispersion of PET crystalline region was enhanced properly through transesterification. The shape fixity was increased as the crystallinity of PCL block was increased.

Polycaprolactone(PCL)과 poly(butylene terephthalate) (PBT)를 1,4-butane diol(BD) 존재 하에서 에스테르 교환반응을 시킨 후 4,4'-diphenylmethane diisocyanate(MDI)로 사슬연장시키는 방법으로 PCL-PBT 블록공중합체를 효과적으로 합성할 수 있었다. PCL-PBT 블록공중합체는 PCL 블록의 녹는점 이상에서 결정-고무상 전이에 의한 탄성율의 큰 감소를 보였다. 에스테르 교환반응 정도가 커 PCL 블록의 결정화도가 작을수록 녹는점 이하에서의 탄성율은 감소하였으며, 녹는점 이상에서의 탄성율은 에스테르 교환반응 정도가 커 PBT 결정영역의 미세분산이 클수록 증가하였다. PCL-PBT 블록공중합체의 형상회복능은 에스테르 교환반응 정도가 커 PBT 결정영역의 미세분산이 클수록 증가하였으나, 과다한 에스테르 교환반응이 진행되면 오히려 감소하였다. 또 PCL 블록의 함량이 많을수록 형상회복력은 컸으며, PCL 블록의 결정성이 클수록 형상고정능이 증가하였다.

Keywords: PCL-PBT Block Copolymer; Shape Memory Effect; Transesterification