Direct method of synthesis of polyureas by N-acylphosphoramidites

Polyureas and polythioureas were prepared under mild conditions by direct polycondensation of carbon dioxide and carbon disulfide, respectively, with diamines in the presence of diethyl N-acetyl-N-methylphosphoramidite or its analogs containing an active PN bond. The influence of the substituents in the phosphoramidite, of the CO2 pressure, solvent, organic base and diamine structure on the yield and inherent viscosity of the polymer was investigated. A reaction mechanism involving the intermediate formation of a mixed anhydride of dialkylphosphorous and alkyl(aryl)carbamic acid is discussed.