Tunable synthesis of starch-poly(vinyl acetate) bioconjugate

Starch-poly(vinyl acetate) bioconjugate of controllable composition and structure was generated via a combination of RAFT polymerization and copper-catalyzed alkene-azide cycloaddition. Firstly, well-defined alkyne-terminated poly(vinyl acetate) (AT-PVAc) was prepared by RAFT polymerization of vinyl acetate in the presence of an alkyne-containing chain transfer agent. Secondly, azide-functionalized starch (SN) was synthesized by the nucleophilic substitution reaction of starch tosylate and sodium azide. Then, the bioconjugate was obtained through the click reaction of AT-PVAc and SN. FTIR, elemental analysis, and NMR were used to verify the structure of the intermediates and the bioconjugate. GPC measurements showed that the MW of AT-PVAc linearly depended on the monomer conversion and the polydispersity indexes ranged from 1.09 to 1.28. TEM analysis exhibited the final product was able to self-assemble into micelles in aqueous medium, which suggested the product was amphiphilic and confirmed the successful conjugation of starch and PVAc once more. The content of starch in the bioconjugate could be 47.8-89.2%, which was able to be tailored by the feeding ratio of SN/AT-PVAc and the MW of AT-PVAc.