Synthesis and Thermal Properties of Poly(benzoxazole)s Based on Pendants

A series of wholly aromatic poly(hydroxyamide)s(PHAs), containing varying amounts of 2,6-dimethylphenoxy group and quinoxaline ring in the main chain, were synthesized by a direct polycondensation method. The inherent vis- cosities of the PHAs in either DMAc or DMAc/LiCl solution at 35 o C were found to be in the range of 1.02~1.90 dL/g. 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 on heating; however, PHA 4, PHA 5, and PHA 6 could be dissolved in aprotic solvents on heating without LiCl. For poly(benzoxazole)s(PBOs), the 10% and maximum weight loss temperatures were in the range of 582~622 o C and 630~659 o C, respectively. Residues of PBOs at 900 o C were found to be relatively high, which were in the range of 65.3~70.8%.