Enantioselective enzymatic modification of chiral block copolymers

Block copolymers comprising blocks with pendant hydroxy groups of opposite chirality are synthesized by RAFT polymn. of (R)- and (S)-1-(4-vinylphenyl)ethanol (1R and 1S) as monomers. Initially, poly(styrene) macro-RAFT agents are chain-extended with both enantiomeric monomers to obtain poly(styrene-b-1R) and poly(styrene-b-1S) with controlled mol. wt. and low polydispersities. Enantioselective esterification with vinyl acetate by Candida Antarctica Lipase B (CALB) is only possible on the 1R-contg. block copolymer. This concept is extended to a series of chiral block copolymers poly(1R-b-1S) which, apart from their optical rotation, all behave like very similar homopolymers. By enzymic enantioselective esterification on the 1R-block, block copolymer structures were obtained.