• Elastomers and Composites
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• v.53 no.3
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• pp.141-149
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• 2018

A series of aromatic poly(o-hydroxyamide)s (PHAs) were synthesized by the direct polycondensation reaction of 4,4′-(2,3-quinoxalinedioxy) dibenzoic acid and/or 4,4′-(2,3-pyridinedioxy) dibenzoic acid with bis(o-aminophenol) including 2,2-bis-(amino-4-hydroxyphenyl)hexafluoropropane. The PHAs exhibited inherent viscosities in the range of 0.17-0.35 dL/g at $35^{\circ}C$ in a DMAc solution. These polymers showed low inherent viscosities and yielded brittle films. All the PHAs showed excellent solubility in aprotic solvents such as DMAc, DMSO, NMP, and DMF at room temperature and in less polar solvents such as pyridine and THF. However, all the PBOs were only partially soluble in $H_2SO_4$. The PBOs exhibited 10% weight loss at temperatures in the range of $537-551^{\circ}C$. The maximum weight loss temperature increased with an increase in the content of the quinoxaline-containing monomer. The residue of the PBOs showed a weight loss of 45.8-56.7% at $900^{\circ}C$ in a nitrogen atmosphere.

• Elastomers and Composites
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• v.52 no.2
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• pp.143-153
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• 2017

Herein we studied the characterization of the PBO films formed via solution casting and thermal cyclization of poly(o-hyroxyamide)s(PHAs) that were synthesized by direct polycondensation of 3,3'-dihydroxybenzidine with 4,4'-(2,3-quinoxalinedioxy) dibenzoic acid and/or 4,4'-(2,3-pyridinedioxy) dibenzoic acid. All the PHAs exhibited inherent viscosities in the range of 0.55~0.84 dL/g in DMAc solution. The copolymers, CPH-2-5, were partially soluble in less polar solvents like pyridine and THF. However, all the PBOs were not soluble in polar solvents, but only partially soluble in sulfuric acid. The temperatures corresponding to 10% weight loss of the PBOs with increasing content of quinoxalinedioxy unit were higher than those of the PHAs, and the char yields at $900^{\circ}C$ in $N_2$, tensile strength, and initial modulus of the PBOs were 1.1~1.3 times, 1.2~1.8, and 1.6~3.3 times higher, respectively, than those of the PHAs. The LOI value of CPB-2 was 38.5%, while that of CPB-1 was the highest at 40.0%. The LOI test confirmed that excellent flame retardants were synthesized.