Phosphorus-containing polyurethans of the formula were prepared by interfacial polymerization of 1,4-butanebischloroformate and p-xylylene-α, α-bischloroformate with bis(m-aminophenyl)alkylphosphine oxides. The polymers had number average molecular weights up to 8600. A test of the stability to alkali of one of the polymers (R?CH3, X?1,4-C6H4) showed it to be as resistant as nonphosphorus analogs, and a film of this polymer exhibited self-extinguishing properties. Thermal degradation of the phosphorus polymers, which began at approximately 230°C, occurred by an initial first-order process, releasing chiefly carbon dioxide. The energies of activation for the maximum rates of weight loss were 31–37 kcal/mole.
