Effect of quaternary phosphonium salts as cocatalyst for epoxide/CO2 copolymerization catalyzed by Salen-type Cr(III) complexes

Organic quaternary phosphonium salts are used in conjunction with chromium Salen complexes in the alternating copolymerization of CO2 and cyclohexene oxide (CHO) and propylene oxide (PO). Highly efficient formation of atactic polycarbonate with narrow molecular distribution and weights comparable or superior to those obtained with Bis(triphenylphosphine)iminium salts (PPNX) can be achieved with UHFFA and TPPCl. Besides, in the case of CHO, FTIR/ATR spectroscopy on the pretreated catalytic system can reliably predict the success of the copolymerization before the introduction of the epoxide monomer.