Based on molecular modelling, the enzyme Candida antarctica lipase B was redesigned as a catalyst for the ring opening polymerization of D,D-lactide. Two mutants with 90-fold increased activity as compared to the wild-type enzyme were created. In a preparative synthesis of poly(D,D-lactide) the mutants greatly improved the rate and the degree of polymerization. 相似文献
Two initiators containing a cleavable ester bond were compared in the lipase‐catalyzed ROP of CL and PDL. The results show that transesterification reactions are present at high rates throughout the enzymatic ROP and start at low conversion. HEA and HEMA displayed similar reaction efficiencies as initiators (acyl acceptors) in the enzymatic ROP. However, transacylation reactions on the HEA‐initiated polyesters were found to be 15 times faster. While in both cases the amount of HEA‐ and HEMA‐initiated polymers could be maximized by short reaction times, a well‐defined (meth)acrylation by this approach was not possible. Our results show that transesterification reactions have to be considered when performing an enzyme‐catalyzed ROP.
Summary: An enzymatic one‐pot procedure has been developed for the synthesis of difunctional polyesters containing terminal thiols and acrylates. Candida antarctica lipase B was used as a catalyst for the ring‐opening polymerization of ω‐pentadecalactone. The polymerization was initiated with 6‐mercaptohexanol, then terminated with γ‐thiobutyrolactone or vinyl acrylate to create two types of difunctional polyesters with a very high content of thiol‐thiol or thiol‐acrylate end‐groups.
