Copper-Mediated CRP of Methyl Acrylate in the Presence of Metallic Copper: Effect of Ligand Structure on Reaction Kinetics

• Published in: Macromolecules 2012-01, Vol.45 (1), p.78-86
• Main Authors: Zhang, Yaozhong, Wang, Yu, Peng, Chi-how, Zhong, Mingjiang, Zhu, Weipu, Konkolewicz, Dominik, Matyjaszewski, Krzysztof
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma201963c

The kinetics of copper-mediated controlled/living radical polymerization (CRP) of methyl acrylate (MA) in the presence of Cu0 and two different ligands that form active catalyst complexes with copperTPMA (tris­(2-pyridylmethyl)­amine) and Me6TREN (tris­(2-(dimethylamino)­ethyl)­amine)are compared. The critical difference between the ligands is that TPMA forms a CuI complex that undergoes essentially no disproportionation in a mixture of MA and dimethyl sulfoxide (DMSO), DMSO/MA (v/v = 1/2), while the complex with Me6TREN undergoes disproportionation to a limited extent. Parameters such as the surface area of Cu0 wire, the concentration of added CuIIX2/L, and ligand concentration were examined. Both the Me6TREN- and TPMA-based catalysts efficiently controlled the polymerization of MA. The TPMA-based system showed a power law order of 0.47 for the apparent propagation rate constant with the Cu0 surface area, very similar to the reported value for the Me6TREN-based system, which showed a power law of 0.44. These results demonstrate that the polymerization of MA in DMSO in the presence of metallic copper can be explained by a core atom-transfer radical polymerization (ATRP) process in which the Cu0 acts as a supplemental activator and reducing agent, rather than through the proposed single-electron-transfer living radical polymerization (SET-LRP) mechanism, which requires additional assumptions, such as complete and instantaneous disproportionation of CuI/L species.