Formation and Structure of Hydrolytic Methylaluminoxane Activators |
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Authors: | Dr Scott Collins Dr Anuj Joshi Prof Mikko Linnolahti |
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Institution: | 1. Former affiliation: Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2 Canada).;2. UVic Genome BC Proteomics Research Centre sup, 4464 Markham St #3101, Victoria, BC V8Z 5N3 Canada;3. Department of Chemistry, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, 80100 Joensuu, Finland |
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Abstract: | Methylaluminoxane (MAO) activators have sheet structures which form ion-pairs on reaction of neutral donors such as octamethyltrisiloxane (OMTS). The ion-pairs can be detected by electrospray ionization mass spectrometry (ESI-MS) in polar media. The growth of these reactive precursors during hydrolysis of Me3Al can be monitored using ESI-MS. Density functional theory, combined with numerical simulation of growth, indicates that this process involves rapid formation of low MW oligomers, followed by assembly of these species into low MW sheets. These can grow through further addition of low MW oligomers or by fusion into larger sheets. The mechanism of these growth processes leads to the prediction that even-numbered sheets should be favored, and this surprising result is confirmed by ESI-MS monitoring experiments of both activator growth and MAO aging. |
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Keywords: | aggregation DFT ESI-MS methylaluminoxane numerical simulation |
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