Series of Azobenzothiazole-Based Initiators for Atom Transfer Radical Polymerization of Methyl Methacrylate

Abstract

2-Bromo-2-methyl-propionic acid 4-benzothiazole-2-ylazo-phenyl ester (BPBE), 2-bromo-2-methyl-propionic acid 4-(6-methoxy-benzothiazole-2-ylazo)phenyl ester (BPMBE) and 2-bromo-2-methyl-propionic acid 4-(6-nitro-benzothiazole-2-ylazo)phenyl ester (BPNBE) were synthesized and acted as initiators for the heterogeneous atom transfer radical polymerization of methyl methacrylate under copper(I) bromide/2,2'-bipyridine catalytic system, respectively. The azobenzothiazole-based end group of polymethyl methacrylate was characterized via UV-visible spectroscopy. All rates of polymerizations exhibited first-order kinetic with respect to the monomer and a linear increase in the number-average molecular weight with increasing monomer conversion was observed for all these initiation systems. The polydispersity indices of the polymethyl methacrylates were relatively low (1.08-1.37) up to high conversions at 60 ºC. Moreover, the initiation systems exhibit a high activity that polymerizations could even be performed at ambient temperature (30 ºC).