Atom transfer polymerisation of methyl methacrylate : use of chiral aryl/alkyl pyridylmethanimine ligands; with copper(I) bromide and as structurally characterised chiral copper(I) complexes

• Published in: Journal of materials chemistry Vol. 8; no. 7; pp. 1525 - 1532
• Main Authors: HADDLETON, D. M, DUNCALF, D. J, KUKULJ, D, HEMING, A. M, SHOOTER, A. J, CLARK, A. J
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 1998
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Schiff base; Cationic complex; Free radical polymerization; Organic ligand; Methyl methacrylate polymer; Kinetics; Complex catalyst polymerization; Experimental study; Catalyst activity; Copper Complexes; Pyridine derivatives
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/a800467f

The use of chiral catalysts in the living radical polymerisation of methyl methacrylate via atom transfer polymerisation (ATP) has been investigated in an effort to control the stereochemistry of the polymer backbone. Two enantiomerically pure chiral catalysts have been prepared and used in the ATP of methyl methacrylate: the structurally characterised complex, bis[N-(1-phenylethyl)-2-pyridylmethanimine]copper(I) tetrafluoroborate, [Cu(C sub 14 H sub 14 N sub 2 ) sub 2 ] [BF sub 4 ], and the reaction product of copper (I) bromide with N-(1-cyclohexylethyl)-2-pyridylmethanimine, [Cu(C sub 14 H sub 20 N sub 2 ) sub 2 ][Br]. Both catalysts were found to be suitable for the ATP of methyl methacrylate in conjunction with either ethyl 2-bromo-2-methylpropanoate in xylene at 90 deg C or 4-methoxybenzenesulfonyl chloride in diphenyl ether at 90 deg C. The system yields polymer of relatively narrow polydispersity; however, the use of these chiral catalysts did not significantly affect the stereochemistry of the polymer backbone. This may be due to the chiral center being too distant from the propagating site to exert any influence over the monomer addition step, or that the reaction proceeds via a completely free-radical mechanism. This is, however, the first time a discrete, structurally characterised copper complex has been used as an effective ATP catalyst. The bond lengths of the complexed ligand indicate the oxidation state of the Cu to be +1 in the complex.