Atom transfer radical polymerization of functional monomers employing Cu-based catalysts at low concentration: Polymerization of glycidyl methacrylate

摘要

Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of an epoxide-containing monomer, glycidyl methacrylate (GMA), was successfully carried out using low concentration of catalyst (ca. 105 ppm) at 60 °C in anisole. The copper complex of tris(2-pyridylmethyl)amine was used as the catalyst, diethyl 2-bromo-2-methylmalonate as the initiator, and 2,2′-azobisisobutyronitrile as the reducing agent. When moderate degrees of polymerization were targeted (up to 200), special purification of the monomer, other than removal of the polymerization inhibitor, was not required to achieve good control. To synthesize well-defined polymers with higher degrees of polymerization (600), it was essential to use very pure monomer, and polymers of molecular weights exceeding 50,000 g mol~(-1) and M_w/M_n = 1.10 were prepared. The developed procedures were used to chain-extend bromine-terminated poly(methyl methacrylate) macroinitiator prepared by activators regenerated by electron transfer (ARGET) ATRP. The Sn~(II)-mediated ARGET ATRP technique was not suitable for the polymerization of GMA and resulted in polymers with multimodal molecular weight distributions. This was due to the occurrence of epoxide ring-opening reactions, catalyzed by Sn~(II) and Sn~(IV).