Preparation of phosphorus‐containing polymers. XXV. Polyamide‐imides that contain phenoxaphosphine rings

New phenoxaphosphine‐containing polyamide‐imides were prepared by cyclodehydration of the polyamide‐amic acids obtained from 8‐chloroformyl‐10‐phenylphenoxaphosphine‐2,3‐dicarboxylic anhydride 10‐oxide and diamines by a low‐temperature solution polycondensation. Polymers with reduced viscosities of 0.10–0.59 dl/g in DMA or concentrated H 2 SO 4 at 30°C were obtained in 64–97% yields. All the polyamide‐imides were soluble in m ‐cresol, concentrated H 2 SO 4 , and dichloroacetic acid and some of them were soluble in DMF, DMA, and DMSO; the polyamide‐imides had better solubility in organic solvents than phenoxaphosphine‐containing polyimides. The phenoxaphosphine‐containing polyamide‐imides derived from aromatic diamines exhibited excellent thermal properties and little degradation below about 400°C, whereas the polymers from aliphatic diamines began to lose weight at about 250°C. They appeared to have thermal stability between phenoxaphosphine‐containing polyimides and polyamides. These polyamide‐imides exhibited self‐extinguishing behavior.