Multiarm heteroblock star-type

Multiarm heteroblock star-type copolymers of poly(lactic acid) (PLA) and poly(e-CL), poly(LA-co-e-CL) were prepared via a chemoenzymatic route [90]. Firstly, ROP of e-CL was initiated regioselectively from 6-OH site of ethyl glucopyrano-side (EGP) (see also above) using porcine pancreatic lipase as catalyst followed by termination of the EGP-PCL-OH terminus by lipase-catalyzed acetylated using vinyl acetate. Subsequently, Sn-catalyzed ROP of lactide was initiated from 2-, 3- and 4-OH groups of EGP to give a copolymer consisting of one poly(e-CL) arm with M = 1300 and three PLA arms so that the M of the final product was 11500 (Scheme 4.25). 

Scheme 4.25 Synthesis of multiarm heteroblock star-type copolymer via chemoenzymatic route.

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