Copolymerization of carbon dioxide with propyleneimine

Carbon dioxide and propyleneimine were allowed to copolymerize without using any catalyst to give a polyurethane with a carbon dioxide content of 10–35 mole‐%. The polymer yield, the specific viscosity, and the content of carbon dioxide in the copolymer increased with increasing polymerization temperature. The infrared spectrum of the copolymer showed the characteristic peak assignable to a cyclic urethane(4‐methyl‐oxazolidone‐2) at 1750 cm−1 as well as the peak characteristic of the urethane linkage at 1700 cm−1. The relative intensity ratio of the former absorption to the latter decreased markedly with increasing polymerization temperature. Propyleneimine did not polymerize at all in the absence of carbon dioxide. Polymerizations were also carried out with the use of various solvents. On the basis of these results, a probable reaction scheme of the copolymerization was proposed.