An ionic liquid as reaction media in the ring opening graft polymerization of ε-caprolactone onto starch granules

A powerful and highly efficient direct solvent, 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), has been used for the dissolution of starch and the homogeneous ring opening graft polymerization (ROGP) of ε-caprolactone (ε-CL) onto starch granules. The ROGP carried out smoothly and the grafting efficiency of PCL reached 24.42% when the ROGP proceeded at 110 °C for 28 h with ε-CL/starch 1:1 (wt/wt) and stannous octoate (Sn(Oct)2) as a catalyst, which was calculated according to a standard curve newly created by an FT-IR method. The structure of starch grafted poly(ε-caprolactone) (starch-g-PCL) was characterized by FT-IR, DSC, WAXD and 13C NMR, the good adhesion between the two components was evidenced by SEM observations. The homo-polymerization of ε-CL and the disconnection of grafted PCL from starch-g-PCL were the main competition reactions. A new homogeneous modification of starch by the ROGP of ε-CL in [AMIM]Cl was investigated, as well as a new FT-IR method to calculate the grafting efficiency of PCL.