Copolymerization of carbon dioxide and oxetane catalyzed by aluminum porphyrin complex system

Tetraphenylporphinatoaluminum chloride ([TPP]AlCl) catalyst and tetra-n-butylammonium bromide (TBAB) cocatalyst system is effective for the copolymerization of CO2 and oxetane even under low CO2 pressure (similar to 2 MPa). In the presence of toluene as a solvent, poly(trimethylene carbonate) (PTMC) containing >99% of carbonate linkages with M-n = 8600 and M-w/M-n = 1.70 was synthesized. This is the first report of PTMC formation with excellent ratio of carbonate linkages from oxetane and CO2. According to the kinetic analysis, proton nuclear magnetic resonance (H-1 NMR) and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) measurements of the products, PTMC was mainly synthesized via (i) the trimethylene carbonate (TMC) formation from CO2 and oxetane and (ii) the successive ring-opening polymerization of TMC.