Well-defined oligosaccharide-terminated polymers from living radical polymerization

Abstract

beta-cyclodextrin has been transformed into an initiator for copper(I)-mediated living radical polymerization via successive acetylation, ring opening, and condensation reactions. This glycoinitiator has been successfully used to prepare a range of methacrylate polymers, which show all characteristics of living polymerization. Poly(methyl methacrylate) is prepared with an Mn of 10,100 g/mol (theoretical Mn = 10,900) and polydispersity of 1.09. Excellent first-order kinetics and an evolution of mass with time are presented. Hydrophilic polymers based on poly(ethylene glycol), glucose and tertiary amine monomers are successfully prepared with terminal maltoheptose units. Polymerization of styrene results in a broadening of the polydispersity to 1.48 while maintaining good control over the Mn. The acetyl protecting groups on the maltoheptose terminal unit are easily removed in all cases to give the hydroxylated sugar, as shown by NMR. These results demonstrate the applicability of utilizing glycoinitiators as a new, versatile route to a wide range of glycopolymers. The polymerization chemistry is inert to the sugar functionality allowing glyco units to be precisely placed within a synthetic macromolecule with all the associated advantages of living polymerization.