Living radical polymerization of styrene mediated by copper(I)/N-n-alkyl-2-pyridylmethanimine catalysts
UNSPECIFIED. (2002) Living radical polymerization of styrene mediated by copper(I)/N-n-alkyl-2-pyridylmethanimine catalysts. MACROMOLECULES, 35 (8). pp. 2941-2948. ISSN 0024-9297Full text not available from this repository.
Official URL: http://dx.doi.org/10.1021/ma011667o
The polymerization of styrene mediated by copper/N-n-alkyl-2-pyridylmethanimine is reported. Two different types of initiator were employed, viz., 1-phenylethyl bromide, chosen for its similar structure to the final end group of the polymer, and alkyl-2-bromisobutyrates, as models for the synthesis of diblock copolymers via macroinitiators. The copper catalyst structure was varied by changing the alkyl group on the N-n-alkyl-2-pyridylmethanimine ligand where alkyl = propyl (3), pentyl (4), and octyl (5) and used over a temperature range of 90-130 degreesC. At 90 degreesC, polymerization reactions were relatively slow with polymerization taking approximately 7 days to reach 100% conversion, 12 h to reach 36% conversion at 110 degreesC, and 7 h to reach 90% conversion at 130 degreesC. The PDI of the polymer broadens on increasing the temperature, reaching 1.15, 1.17, and 1.32 at 90, 110, and 130 degreesC, respectively, when the reaction was stopped. Thus, 110 degreesC is the optimal temperature for the polymerization of styrene with this type of ligand. The catalyst prepared with N-n-propyl-2-pyridylmethanimine is not completely soluble over all temperatures, and the catalyst solubility affects both the rate and the control of the polymerization. As the length of the alkyl chain increases, the solubility in nonpolar solvent also increases. Hence, N-n-pentyl-2-pyridylmethanimine is the best ligand for copper bromide to ensure homogeneity of the reaction and achieve good control over the polymerization. The effect of the solvent polarity was also investigated to elaborate the optimal polymerization conditions using xylene, anisole, and ethylene glycol diethyl ether. Based on these results, the synthesis of di- and triblock copolymers was undertaken using respectively poly(ethylene glycol) methyl ether and poly(propylene glycol) derived initiators. The latter led to an amphiphilic block copolymer with a low PDI = 1.27 and a molecular weight close to the theoretical value (M SEC = 10 900 mol g(-1)). A large batch (40 g) of block copolymer was synthesized with a block of PS 5000 g mol(-1) by stopping the reaction at 50% conversion, which had [St]/[I] = 100.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Journal or Publication Title:||MACROMOLECULES|
|Publisher:||AMER CHEMICAL SOC|
|Date:||9 April 2002|
|Number of Pages:||8|
|Page Range:||pp. 2941-2948|
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