One-Pot Chemoenzymatic Cascade Polymerization under Kinetic Resolution Conditions

Abstract

A novel concept for the metal-free synthesis of block copolymers combining enzymatic ring-opening polymerization and nitroxide-mediated living free-radical polymerization from a bifunctional initiator is presented. Block copolymers comprising a poly(styrene) and poly(caprolactone) block were obtained in two consecutive polymerization steps (macroinitiation) and in a one-pot cascade approach without intermediate transformation or work up step. By optimization of the reaction conditions a high selectivity of both transformations could be realized in the cascade polymerization, resulting in high block copolymer yields. The same concept was successfully applied to enzymatic resolution polymerization of racemic 4-methyl-ε-caprolactone combined with the living free-radical polymerization of styrene yielding block copolymers with high enantiomeric excess in the 4-methyl-ε-caprolactone block.

Recent Developments in Lipase‐Catalyzed Synthesis of Polyesters

“…[91] The method allows a versatile synthesis of block copolymers consisting of a polyester chain and a vinyl polymer chain by using a designed bifunctional initiator, the reaction routes of which are shown generally in Figure 8. [91,99,101,102] For example, an initiator having both a hydroxy group for eROP and bromine atom for ATRP is to be used. Lipase CA (Novozyme 435)-catalyzed ROP of e-CL (reaction: 5 g of e-CL with 0.5 g of the initiator and 0.5 g of the lipase, 60 8C in toluene for 3 h) to give 3.1 g of poly(e-CL).…”

“…A chiral block copolymer was obtained by using 4-alkyl-CL (4-RCL) as comonomer (Scheme 21). [102] A spontaneous single-step chemoenzymatic synthesis of block copolymers was facilitated in supercritical carbondioxide (scCO 2 ) via route A in Figure 8.…”

Hydrolases Part I: Enzyme Mechanism, Selectivity and Control in the Synthesis of Well-Defined Polymers

“…In the absence of water, high molecular weight polyesters are typically obtained [74,75,108], whereas increasing the water content (which acts as an initiator) leads to a higher number of polymer chains and thus lower molecular weight polyesters [64,101]. Also, the use of initiators containing an alcohol allows the preparation polymers of predictable molecular weight [72,76,109,110].…”

Chiral Polymers by Lipase Catalysis

“…A similar approach was followed with the eROP of 4 -MeCL, followed by nitroxide mediated living free radical polymersation (NMP) of styrene using a bifunctional catalyst (Scheme 11.18 ) [62] . Styrene, the monomer for the NMP, was added already at the beginning since it proved to be a good solvent for the eROP of lactones.…”