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[T1.sub.[rho]] RELAXATION STUDIES OF METHYLALUMINOXANE.

[T1.sub.[rho]] RELAXATION STUDIES OF METHYLALUMINOXANE. Amy [Campbell.sup.1], Anthony A. [Mrse.sup.2], Leslie G. [Butler.sup.2], Department of Chemistry, University of North [Alabama.sup.1], Florence, AL 35632, Louisiana State [University.sup.2], Baton Rouge, LA 70803

ABSTRACT

One proposed structure of methylaluminoxane (MAO), a polypropylene co-catalyst, contains two types of methyl groups, one bridging and one terminal. The possibility of two types of methyl groups existing in MAO has been explored by solid-state [1.sup.H] Nuclear Magnetic Resonance (NMR) [[T.sub.1].sub.[rho]] relaxation time data. A significant difference in [[T.sub.1].sub.[rho]values] would indicate that the two types of methyl groups exist. [[T.sub.1].sub.[rho]] relaxation time data were collected as a function of [B.sub.1] field strength and as a function of temperature on two slightly different samples of

MAO: MAO solid and MAO gel. MAO gel, while similar to MAO, is believed to have more chemical bonds between major MAO structural units; some of those bonds may prove to be bridging methyl groups. Data analysis was performed using a Mathematica least square analysis which was calculated using double exponential fits. This yielded the [[T.sub.1].sub.[rho]] values and compositions. Activation energies for MAO were then obtained by fitting the [[T.sub.1].sub.[rho]] data as a function of temperature. The activation energy for the bridging methyl group could not be reliably measured, probably due to a distribution of strength of bridge bonding. The measurements as a function of [B.sub.1] strength were designed to assess the range of bridge bonding strengths.

This work has practical applications in the industry. A major objective is to help in development of process control technology for the industrial synthesis of MAO.
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Publication:Journal of the Alabama Academy of Science
Article Type:Brief Article
Geographic Code:1USA
Date:Apr 1, 2001
Words:298
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