1H-NMR과 WAXS를 이용한 폴리(트리메틸렌 테레프탈레이트)/폴리(트리메틸렌 나프탈레이트) (50/50) 블렌드의 에스터 교환반응 연구

Abstract

Poly(trimethylene terephthalate) (PTT) and poly(trimethylene naphthalate) (PTN) blends of 50/50 weight ratio, T5N5, were prepared by solution blending-precipitation method, and the effect of melting time on the degree of randomness, sequence length, and crystalline structure of melt-pressed blends obtained by melting T5N5 on a hot stage at 260oC for different times and quenching into liquid nitrogen was studied using DSC, 1H-NMR and WAXS. The T5N5 blend showed two Tgs corresponding to that of PTT and PTN, which indicated that PTT and PTN were immiscible. But the melt-pressed blends melted at 260oC for 2 minutes or more showed single Tg indicating that the system became miscible. 1H-NMR analysis confirmed that the blends became block copolymers and that the degree of randomness increased as melting time increased. The sequence length of PTT component was larger than that of PTN in the resultant copolymer. Although PTT and PTN were present in the same amount in the blend, PTT component crystallized more easily than the PTN component due to the larger block length of PTT. The crystalline structure of the component polymers was the same as that of homopolymers. The WAXS patterns showed that the crystalline structure of PTN in the melt-pressed blends was b-form when they were annealed at 180oC but it was a-form when annealed at 140oC, exhibiting the same behavior as homo PTN.