Facile and efficient synthesis of hyperbranched polyesters based on renewable castor oil

Hyperbranched polyesters with thioether linkages were facilely prepared from methyl 10-undecenoate, a castor oil-derived renewable chemical. The monomer was obtained in excellent yield through thiol-ene click chemistry in the presence of catalytic amounts of photoinitiator under UV irradiation. Subsequent bulk polycondensation via a transesterification process catalyzed by Ti(OBu) 4, Sb2O3 or Zn(OAc) 2 gave hyperbranched polyesters with high molecular weights and unusual crystalline properties. The degree of branching in the range 0.45-0.54 calculated from quantitative 13C NMR spectroscopy and low inherent viscosities of 0.16-0.25 dL g-1 strongly confirmed the hyperbranched structures of the resultant polymers. (C) 2012 Society of Chemical Industry