Chemoenzymatic synthesis methacrylate

Sha et al. applied the commercially available dual initiator ATRP-4 for the chemoenzymatic synthesis of block copolymers. In a first series of publications, the group reported the successful synthesis of a block copolymer comprising PCL and polystyrene (PS) blocks [31, 32]. This concept was then further applied for the chemoenzymatic synthesis of amphiphilic block copolymers by macroinitiation of glycidyl methacrylate (GMA) from the ATRP functional PCL [33]. This procedure yielded well-defined block copolymers, which formed micelles in aqueous solution. Sha et al. were also the first to apply the dual enzyme/ATRP initiator concept to an enzymatic polycondensation of 10-hydroxydecanoic acid [34]. This concept was then extended to the ATRP of GMA and the formation of vesicles from the corresponding block copolymer [35]. 

Wyatt, M.F., Duxbury, C.J., Thurecht, K.J., and Howdle, S.M. (2006) One-Step Chemoenzymatic synthesis of poly(e-caprolactone-block-methyl methacrylate) in supercritical C02. Macromolecules, 39 (16), 5352-5358. 

Compartmentalization by sequential monomer addition was also successfully demonstrated in the chemoenzymatic synthesis of block copolymers in SCCO2 using lH,lH,2H,2H-perfluorooctyl methacrylate (FOMA) as an ATRP monomer. Detailed analysis of the obtained polymer P(FOMA-i>-PCL) confirmed the presence of predominantly block copolymer structures (16). The clear advantage of the SCCO2 in this approach is that unlike conventional solvents it solubilises the fluorinated monomer. 

We investigated the chemoenzymatic synthesis of block copolymers combining eROP and ATRP using a bifunctional initiator. A detailed analysis of the reaction conditions revealed that a high block copolymer yield can be realized under optimized reaction conditions. Side reactions, such as the formation of PCL homopolymer, in the enzymatic polymerization of CL could be minimized to < 5 % by an optimized enzyme (hying procedure. Moreover, the structure of the bifunctional initiator was foimd to play a major role in the initiation behavior and hence, the yield of PCL macroinitiator. Block copolymers were obtained in a consecutive ATRP. Detailed analysis of the obtained polymer confirmed the presence of predominantly block copolymer structures. Optimization of the one-pot procedure proved more difficult. While the eROP was compatible with the ATRP catalyst, incompatibility with MMA as an ATRP monomer led to side-reactions. A successfiil one-pot synthesis could only be achieved by sequential addition of the ATRP components or partly with inert monomers such as /-butyl methacrylate. One-pot block copolymer synthesis was successful, however, in supercritical carbon dioxide. Side reactions such as those observed in organic solvents were not apparent. 

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