Preparation of CO2-based poly(carbonate-co-lactide) with different porphyrin aluminum (III) catalysts

Abstract

Two-component catalysts composed of tetra (para-X substituted) phenylporphyrin aluminum (III) chloride, T (p-X-P)PAlCl, (where X = H, F, Cl, Br, CH₃, OCH₃, tert-butyl), and cocatalyst bis(triphenylphosphine)imminium chloride (PPN⁺Cl⁻), could initiate the polymerization of propylene oxide (PO). And they could react with rac-lactide, (rac-LA), in the presence of propylene oxide (PO), to yield chains of enriched isotactic polylactide (PLA) with trace polyether segment. Also, these catalysts displayed different catalytic activity in the copolymerization of CO₂ and PO, resulting in poly(carbonate-co-ether) copolymer with different carbonate unit content (CU%). Further, these catalysts could initiate one-pot regio- and stereo- selective terpolymerization of rac-LA, CO₂ and rac-PO, resulting in multi-blocky poly(carbonate-co-lactide) with trace polyether segment. The structure of the products was verified by ¹H NMR, ¹³C NMR, GPC, and DSC analysis, and it was found that variation of substitution groups in the periphery of porphyrin ligand would affect on the catalytic efficiency of ter-polymerization, and the relative polymerization reaction ratio of the ring-opening polymerization of LA (ROP) to the ring-opening copolymerization of PO and CO₂ (ROCOP), resulting in ter-polymer with different contents of PLA segment and PPC segment. However, H-T% in polycarbonate unit and P_i% in polylactide unit did not vary much with the change of catalysts.