Catalyst separation in atom transfer radical polymerization

• Published in: Progress in polymer science Vol. 29; no. 10; pp. 1053 - 1078
• Main Authors: Shen, Youqing, Tang, Huadong, Ding, Shijie
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2004; Elsevier Science
• Subjects: Applied sciences; Atom transfer radical polymerization (ATRP); Catalyst separation; Catalyst supporting; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Catalyst supporting; HMTETA; DMAEMA; Catalyst separation; PMDETA; PSM; ATRP; Bipy; NMP; PST; DAP; PEG; MA; PE; TPP; Atom transfer radical polymerization (ATRP); DiPA; ICP; nBMA; RAFT; TEDETA; Me 6TREN; Purification; Atom transfer polymerization; Living polymer; Physical separation; Review; Complex catalyst; Supported catalyst
• ISSN: 0079-6700; 1873-1619
• DOI: 10.1016/j.progpolymsci.2004.08.002

Atom transfer radical polymerization (ATRP) is a living radical polymerization process utilizing transition-metal complexes as catalysts to mediate the propagation of the polymerization. It is a very versatile process and can synthesize a wide spectrum of polymers with controlled structures. However, a high concentration of soluble catalyst is required in the ATRP process. These catalysts generally co-precipitate in the products as contaminants. Thus, a remaining challenge in ATRP is how to efficiently and economically remove/reduce the catalyst residue from its products, especially for large-scale industrial productions. Post-purification such as reprecipitation, washing, adsorbing with ion-exchange resins, and passing columns of alumina or silica gel has been used on small lab scales. Biphasic catalysis of liquid–liquid biphase (fluorocarbon–organic solvents, ionic liquid–organic solvents) and liquid–solid biphase (solid phase ATRP, solid-supported catalysts by physical adsorption and by covalent bonding, soluble/recoverable supported catalysts, immobilized/soluble hybrid system) has been explored for ATRP. In spite of the advantages of easy catalyst separation/recovery and possibility of scaling up, its control over the polymerization generally deteriorates compared with homogeneous catalysis. Finally, a reversible catalyst supporting concept that is homogeneous for catalysis but heterogeneous for separation/recovery is presented. The development and characters of each system are critically reviewed.