One-pot regioselective and stereoselective terpolymerization of rac-lactide, CO2 and rac-propylene oxide with TPPMCl (M = Cr, Co, Al)/PPNCl binary catalyst

Tetraphenyl porphyrin metal compound (TPPMCl) (where the TPPMCl was TPPCrCl, TPPCoCl, TPPAlCl), in combination with cocatalyst PPNCl (bis(triphenylphosphine)iminium chloride, the molar ratio of TPPMCl to PPNCl was 1:0.5), was used to catalyze the polymerization of racemic lactide (rac-LA) in racemic propylene oxide (rac-PO) medium and the terpolymerization of rac-LA, CO2 and rac-PO. It was found that these TPPMCl/PPNCl binary catalysts could initiate the stereoselective polymerization of rac-LA in rac-PO medium to form enriched isotactic polylactide (PLA) (P-i 68.0%) and terpolymerization of CO2, rac-LA, rac-PO to form PPC-PLA-PPO (PPC, poly(propylene carbonate); PPO, poly(propylene oxide)) multiblock copolymer. In particular the PPC-PLA-PPO multiblock copolymer thus formed displayed high regioregularity and stereoregularity, and has high head-to-tail structure content in the PPC block (H-T% 63.6%) and high isotacticity in the PLA block (P-i 64.0%). The influence of catalyst formula, the monomer feeding ratio, reaction temperature, carbon dioxide pressure and reaction time on the terpolymerization was investigated by H-1 NMR, C-13 NMR, gel permeation chromatography, DSC and TGA. (c) 2018 Society of Chemical Industry