Amide functional initiators for transition-metal-mediated living radical polymerization

Amide initiators were used successfully for copper-mediated living radical polymerization (often called ATRP) of a range of methacrylates to narrow molecular weight homopoymers and block copolymers from initiator species containing a bromo-2-methylpropionamide. The polymerization of methyl methacrylate (MMA) occurs efficiently with a copper chloride (Cu(I)Cl)/N-n-octyl-2-pyridylmethanimine catalyst by maintaining a relatively low temperature for initiation and slowly increasing to the reaction temperature. By keeping the reaction at 25 degrees C for 30 min before heating to 90 degrees C, a number-average molecular weight (M-n) of 12 900 g mol(-1) and a polydispersity of (PDI) = 1.24 at 70% conversion (where [MMA]/[initiator] = 100) were obtained. The polymers produced showed molecular weights in good agreement with the theoretical and polydispersities of 1.20. Where the reaction was heated to 90 degrees C, immediately high mass was obtained (26 600 g mol(-1)) in low yield (33%). When copper bromide (Cu(I)Br) was used in place of Cu(I)Cl, the obtained mass was Much higher than the theoretical values. Polymerization from an initiator based on L-alanine under these conditions gave poly(methyl methacrylate) (PMMA) with M-n = 8100 g mol(-1) (PDI = 1.23) as compared to the theoretical value of 5900 at this conversion (58% after 7 h). Polymerization of a other methacrylates including butyl methacrylate (M-n = 8700 (PDI = 1.27), M-n,M-theo = 7000), benzyl methacrylate (M-n = 11 400 (PDI = 1.25), M-n,M-theo = 9700), dimethylaminoethyl methacrylate (DMAEMA) (M-n = 10 900 (PDI = 1.24), M-n,M-theo = 8100), and also poly(ethylene glycol) methacrylate (M-n = 8100 (PDI = 1.24), M-n,M-theo = 6500) were also polymerized. The successful polymerization of styrene using bromo-2-methylpropionamide initiators is also reported with optimum conditions needing 110 degrees C in the presence of Cu(I)Br and N-n-octyl-2-pyridylmethanimine yield polymer with M-n = 5800 (PDI = 1.27). Poly(methyl methacrylate) was also used as macroinitiator with DMAEMA to form an AB block copolymer, confirming the living nature of the polymers (M-n = 34 700 (PDI = 1.25)). A triblock polymer of methyl methacrylate and poly (dimethylsiloxane) (PDMS) was also prepared from a difunctional bromo-2-methylpropionamide poly(dimethylsiloxane) initiator (M-n = 29 600 (PDI = 1.27)).