Synthesis of PMMA-b-PU-b-PMMA tri-block copolymers through ARGET ATRP in the presence of air

Abstract

ARGET (activators regenerated by electron transfer) ATRP (atom transfer radical polymerization) has been suc- cessfully performed (in flasks fitted with rubber septa without the need for use of Schlenk line) in the presence of limited amount of air and with a very small (370 ppm) amount of copper catalyst together with an appropriate reducing agent Cu(0). Novelty of this work is that the poly(methyl methacrylate)-block-polyurethane-block-poly(methyl methacrylate) tri- block copolymers were synthesized for the first time through ARGET ATRP, by using tertiary bromine-terminated polyurethane as a macroinitiator (MBP-PU-MBP), CuBr2 or CuCl2 as a catalyst and N,N,N,N#,N#-pentamethyldiethylene- triamine (PMDETA) or 2,2-bipyridine (Bpy) as a complexing agent. As the polymerization time increases, both the monomer conversion and ln((M)0/(M)) increased and the molecular weight of copolymer increases linearly with increasing conversion. Theoretical number-average molecular weight (Mn, th) of the tri-block copolymers was found to be comparable with number-average molecular weight determined by GPC analyses (Mn, GPC). These results indicate that the formation of the tri-block copolymers was through atom transfer radical polymerization mechanism. 1 H and 13 C NMR spectral methods were employed to confirm chemical structures of synthesized macroinitiator and tri-block copolymers. Mole percentage of PMMA in the tri-block copolymers was calculated using 1 H NMR spectroscopy and was found to be comparable with the GPC results. Additionally, the studies of surface properties (confocal microscopy and SFE) of tri-block copolymer coatings confirmed the presence of MMA segments.