Preparation of flame-retarding poly(propylene carbonate)

A preparative method for a flame-retarding poly(propylene carbonate) (PPC) was demonstrated by employing diphenylphosphinic acid (Ph2P(O)(OH)), phenylphosphonic acid (PhP(O)(OH)2), or phosphoric acid (P(O)(OH)3) as a chain transfer agent in the immortal CO2/propylene oxide copolymerization catalyzed by a highly active catalyst, a cobalt(III) complex of a Salen-type ligand tethered by four quarternary ammonium salts (1). High turnover frequencies of 10 000–20 000 h−1 (700–1300 g-polymer per g-cat·h) were maintained even in the presence of a large amount of the protic chain transfer agent (–OH/1, 1600–200). Directly after the copolymerization using PhP(O)(OH)2 as a chain transfer agent, thermoplastic polyurethane (TPU) was formed by adding a stoichiometric amount of toluene-2,4-diisocynate. The TPU also was not inflammable. Cone calorimeter studies showed that PPC itself and TPU prepared using PPC-diol emitted significantly less smoke while burning than common plastics, such as polystyrene.