Synthesis of Anthracene End-Capped Poly(methyl methacrylate)s via Atom Transfer Radical Polymerization and Its Kinetic Analyses

The synthesis of anthracene end-capped poly(methyl methacrylate)s via atom transfer radical polymerization (ATRP) and the kinetic analyses thereof are reported. Methyl methacrylate was polymerized in toluene at 90 °C (or 60 °C) via ATRP using 9-anthracenemethyl-2-bromoisobutyrate as the initiator and CuBr/ N -( n -hexyl)pyridylmethanimine as the catalyst. Anthracene end-capped polymers with predetermined molecular weights and low polydispersities (PDI < 1.3) were obtained and characterized by 1 H NMR and UV−vis. The initiator and Cu(I) concentrations, initially added Cu(II) concentration, and reaction temperature of the ATRP system have a decisive effect on the kinetics of the reaction. When the initiator and Cu(I) concentrations or the reaction temperature are relatively high, or the initially added Cu(II) concentration is relatively low, and consequently the radical concentration in the system is relatively high, the kinetics of the polymerization fits Fischer's equation (ln([M] 0 /[M]) ∝ t 2/3 ). On the other hand, Matyjaszewski's equation (ln([M] 0 /[M]) ∝ t ) can be fitted quite well when the initiator and Cu(I) concentrations or the reaction temperature are so low or the initially added Cu(II) concentration becomes so high that radical termination is negligible. This kinetic transition is of great importance for better understanding the mechanism of ATRP. The equilibrium and termination constants ( K eq and k t ) for the studied ATRP system at 90 °C are 9.1 × 10 -8 and 1.3 × 10 8 M -1 s -1, respectively. The experimental evidence for Fischer's theoretically derived threshold Cu(II) concentration for the kinetic transition, i.e., [Cu(II)] 0, t = (3 K eq [RX] 0 [Cu(I)] 0 k t / k p ) 1/2, is provided.