Formation of a tunable starch‐based network by in situ incorporation of mercapto groups and a subsequent thiol‐ene click reaction

Abstract A tunable starch‐based hydrogel was prepared by crosslinking unsaturated macromonomers in the presence of H 2 S. First, well‐defined poly(vinyl alcohol) (PVA) was prepared by alcoholysis of poly(vinyl acetate) obtained by reversible addition‐fragmentation chain transfer (RAFT) polymerization of vinyl acetate. Subsequently, carbon‐carbon double bonds were incorporated onto PVA through esterification with maleic anhydride. Finally, the hydrogel was formed via concurrent electrophilic addition and thiol‐ene reaction between starch maleic half‐ester, unsaturated PVA and H 2 S using potassium persulfate as initiator at 60 °C. Elemental analysis showed the percentage of sulfur in the gel ranged from 0.86% to 1.73%, depending on the chain length of PVA. The storage modulus, loss modulus and glass transition temperature of the networks varied from 12.7 to 50.9 MPa, from 3.7 to 15.7 MPa and from 57.0 to 71.8 °C, respectively. Both the swelling and release behavior of the gels were also modulated by changing the unsaturated PVA component. © 2012 Society of Chemical Industry