Aliphatic polyester-grafted starch composites by in situ ring opening polymerization

Catalyzed Ring-Opening Polymerization (ROP) of lactones, such as epsilon -c aprolactone and delta -valerolactone, has been investigated for preparing a liphatic polyester-grafted corn starch compositions. The polymerization has been carried out either in bulk (without solvent) or in 10 wt% granular st arch in toluene suspension, after adequate activation of. the starch surfac e amylose/amylopectin hydroxyl groups into aluminum alkoxides. This activat ion has been done by in situ reaction with triethylaluminum and has proved to be very effective in promoting fast ROP and also covalent grafting of th e polyester chains onto the starch surface. Drying of the starch granules c onstitutes a key-step of the proposed process. The actual fixation of the i nitiator onto the starch surface has been checked by XPS analysis whereas g ood adhesion between the two components has been evidenced by SEM observati ons. Growth of the polyester chains on the starch granules has been followe d by the increase of the mean diameter of the 'encapsulated' granules as at tested by laser scattering granulometry.