[T1.sub.[rho]] RELAXATION STUDIES OF METHYLALUMINOXANE.
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|
|Date:||Apr 1, 2001|
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