Synthesis of ultrahigh molar mass poly(2-hydroxyethyl methacrylate) by single-electron transfer living radical polymerization

Cu(0)/Me6-TREN mediated SET-LRP of 2-hydroxyethyl methacrylate (HEMA) initiated with methyl α-bromophenylacetate (MBrPA) was performed in DMSO at 25 °C targeting [M]0/[I]0 = 100 to 10 000. At [M]0/[I]0 = 100, SET-LRP of HEMA is a living process, and provided PHEMA with Mn = 21 500 g mol−1 and Mw/Mn = 1.20 in 7 h. Using similar conditions, PHEMA with Mn = 35 000 to 152 200 g mol−1 and Mw/Mn = 1.28 to 1.39 was prepared within 9 h. When targeting higher [M]0/[I]0 (2000 to 10 000), Me6-TREN concentration was changed to 0.15 equivalent with respect to initiator concentration, for at higher ligand concentration the polymerization did not proceed beyond 30% conversion even after a long reaction time. PHEMA with Mn = 333 500 to 1 017 900 g mol−1 and Mw/Mn lower than 1.50 was synthesized for the first time by direct polymerization of HEMA without protecting the hydroxyl group.