Hyperbranched polyesters based on hydroxyalkyl-lactones via thiol-ene click reaction

Abstract

The preparation of AB2 monomers via thiol-ene click reaction from six- and seven-membered unsaturated lactones is described. The hydroxyl-functionalized valerolactone was prepared by use of Michael thiol-ene-addition reaction starting from 2-mercaptoethanol and 3-methylenetetrahydro-2H-pyran-2-on. The hydroxyl-functionalized caprolactone was prepared radically from 2-mercaptoethanol and 7-allyloxepan-2-one. Both AB2 monomers were polymerized via ring opening in the presence of tin(II)-2-ethylhexanoate (Sn(Oct)2) as a catalyst yielding the hyperbranched polyesters. The new hyperbranched polyesters were analyzed by 13C NMR spectra to determine the degree of branching.