Preparation of phosphorus-containing polymers—XVII. Preparation of polyamides containing phenoxaphosphine rings

New phenoxaphosphine-containing polyamides were prepared from 2,8-dichloroformyl-10-phenylphenoxaphosphine 10-oxide (III) and aromatic diamines in DMA by low-temperature solution polycondensation in the presence of triethylamine as acid acceptor. (III) was synthesized by the chlorination of 2,8-dicarboxy-10-phenylphenoxaphosphine 10-oxide derived from 2,8-dimethyl-10-phenylphenoxaphosphine 10-oxide by pyridine-permanganate oxidation. The resulting polyamides had a reduced viscosity of 0.14–0.40 dl/g in DMA or conc. H₂SO₄ at 30°. They were soluble in conc. H₂SO₄ and some of them dissolved in DMA, DMF and DMSO, but all were insoluble in benzene and formic acid, etc. They had good thermal stability, hardly degrading until a temperature of about 400° was reached; they showed resistance to ignition.