Improvement of the control over SARA ATRP of 2-(diisopropylamino)ethyl methacrylate by slow and continuous addition of sodium dithionite

• Published in: Polymer chemistry Vol. 5; no. 16; pp. 4617 - 4626
• Main Authors: Góis, Joana R., Konkolewic, Dominik, Popov, Anatoliy V., Guliashvili, Tamaz, Matyjaszewski, Krzysztof, Serra, Arménio C., Coelho, Jorge F. J.
• Format: Journal Article
• Language: English
• Published: 21.08.2014
• Subjects: Catalysts; Conversion; Copper; Ethers; Ligands; Polymerization; Sodium dithionite; Synthesis
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/C4PY00561A

The kinetics and detailed mechanism of SARA ATRP of 2-(diisopropylamino)ethyl methacrylate (DPA) were investigated. Supplemental activator and reducing agent (SARA) atom transfer radical polymerization (ATRP) using sodium dithionite (Na 2 S 2 O 4 ) was used to create well controlled polymers of PDPA. The influence of the initiator, solvent, structure and concentration of the catalyst was studied, and the ratios of Na 2 S 2 O 4 were adjusted to optimize the polymerization. Well controlled polymers required Na 2 S 2 O 4 to be slowly and continuously fed to the reaction mixture, with 500 parts per million (ppm) of CuBr 2 with tris(2-dimethyamino)amine (Me 6 TREN) as a ligand. The initial content of Na 2 S 2 O 4 in the reaction mixture, the feeding rate and the Cu catalyst concentration were optimized to provide polymers with narrow molecular weight distribution ( M w / M n < 1.15) at high monomer conversion (∼90%). Interestingly, the results revealed that when tris(2-pyridylmethyl)-amine (TPMA) was used as a ligand, the amount of copper required to achieve similar control of the polymerization could be decreased 5 times. This system was successfully extended to the polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA). The high conversion and preservation of the chain-end functionality allows the direct synthesis of POEOMA- b -PDPA block copolymers. The low catalyst concentrations and benign nature of Na 2 S 2 O 4 make this SARA ATRP method attractive for the synthesis of well controlled water soluble polymers for biomedical applications.