Characterization of aluminoxanes by ESR spin probe method

Full Paper: Lewis acidic sites of MAO, EBAO and EAO were studied by the ESR method with TEMPO as a spin probe. The ESR studies on MAO, EBAO and EAO in dicated that different aluminum atoms coexist in aluminoxanes. More Lewis a cidic three-coordinated aluminum atoms were found in EBAO than in MAO and E AO. This obvious difference was attributed to the more irregular structure of EBAO due to stereochemical effects. The different alkyl groups, namely e thyl and iso-butyl groups in EBAO, can greatly disturb the regular structur e of aluminoxane which lead to the formation of more unsaturated aluminum a toms and enhanced activity of EBAO as compared with EAO and BAO.