주사슬에 펜던트를 갖는 전방향족 Poly(hydroxyamide)s의 합성 및 열적 특성

Abstract

A series of wholly aromatic poly(hydroxyamide)s (PHAs), containing varying amounts of dimethylphenoxy group and quinoxaline ring in the main chain, were synthesized by a direct polycondensation method. Six of the final products, PHAs were characterized by using FT-IR, 1H-NMR, TGA, DSC and XRD. The inherent viscosities of the PHAs in either DMAc or DMAc/LiCl solution at 35 ℃ were found to be in the range of 1.02―1.90 dL/g. Then, the PHAs were converted to polybenzoxazoles (PBOs) by a thermal cyclization method. In the solubility study, we observed that PHA 1, PHA 2, and PHA 3 were dissolved in aprotic solvents such as DMAc, NMP, DMF, and DMSO with LiCl upon heating; however, PHA 4, PHA 5, and PHA 6 could be dissolved in the same solvents without heating. In the case of PBOs, they were hardly dissolved in the same solvents; on the other hand, the PBOs were dissolved partly in sulfuric acid. The thermal transition study using DSC indicated that there was a endothermic peak in the range of 207―308 ℃, which was owing to by the thermal cyclization process of PHAs. Thermal stability properties of PHAs and PBOs were characterized by TGA. For PHAs, the maximum weight loss temperatures were in the range of 645―662 ℃. For PBOs, the 10 % and maximum weight loss temperatures were in the range of 575―641 ℃ and 647―665 ℃, respectively. Residues of PHAs and PBOs at 900 ℃ were found to be relatively high, which were in the range of 52.1―61.5 wt% and 58.3―69.0 wt%, respectively.