Organocatalytic Ring Opening Copolymerization of D, L-Lactide and 2- Methyl-2-carboxytrimethylene carbonate: Characterization, PEG Grafting and Selfassembly

摘要

Aliphatic polycarbonates are employed in many biomedical and pharmaceutical applications, owing to their high biocompatibility and good mechanical properties. The classic coordination/insertion mechanism of ring-opening polymerization (ROP) primarily involves electrophilic activation of the monomer by lewis acid metal contains such as Sn ( I I ) . However, i n the presence Sn ( I I ) , most polymerization of cyclic carbonates gave relative broad polydispercity indices. The polydisperse polymer may lead to a broad particle size distribution depending on the micelle preparation process, which may also affect the particle circulation time in vivo when the nanoparticle is used for drug delivery purpose. While extraordinary advances have been made in organometallic catalysis for ring-opening polymerization reaction, organocatalysis complement transition metal catalysis, as the lack of metal residual contaminants that can compromise the polymer performance in biomedical applications'. Recently, a thiourea-amine organocatalyst was tested for solution ROP of LA by Hedrick et al. The molar mass of PLA was well controlled and PDI was also very low (< 1.08). The polymerization reaction was proved to be living and transesterification was not observed.