th  - 1988 - 51st ENC Conference

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NMR IMAGING TECHNIQUES IN MATERIALS SCIENCE
Simon Chu* and David Foxall.
Spectroscopy Imaging Systems, Fremont, CA 94538.
We have used NMR imaging as a non-destructive tool to monitor transition and diffusion
between liquid and solid phases in a number of different practical examples. A major problem
associated with imaging techniqes to date is a lack of ability to quantify fundamental physical
parameters. We have paid strict attention to the problem of obtaining quantitative results from
NMR images.
Adhesives, resins and piasters provide practical examples of systems undergoing
solidification by different mechanisms, which include condensation reaction (silicone glue),
evaporation of solvent (plastic wood filler) and hydration of water (plaster). The
methanol/polymethyl methacrylate system is an example of liquid permeation into solids, of
practical significance in aircraft windshields. Water/agarose provides a controlled model system
for diffusion studies.
We will present results of these systems in the form of imaging time course studies and
analysis to obtain kinetic data and diffusion coefficients. A disscusion of the problems
encountered in making our measurements and how we have attempted to overcome them should
provide some insight into how NMR imaging can be used in materials science studies.
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Ramanathan,
Philadelphia,
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DEVELOPMENTS IN NITROGEN-14 NMR SPECTROSCOPY: R. McNamara, K.V.
and S.J. Opella, Department of Chemsitry, University of Pennsylvania,
Pennsylvania 19104
Recent results which extend the utility of nitrogen-14 NMR spectroscopy will
be presented. The experiments involve measurement of relaxation parameters of
model peptides over a range of temperatures down to liquid helium temperaturs and
of nitrogen-carbon dipolar couplings. For example, t4N overtone decoupling results
in simplification of 13C spectra and helps as an additional assignment tool leading to
structure determination. Two-dimensional NMR experiments that enable
measurement of carbon-nitrogen, dipolar couplings will be presented. The 14N
relaxation data will be discussed in terms of possible sensitivity enhancement at low
temperatures and other applications such as 14N spin exchange experiments.
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