Download Application of NMR techniques in studying the dynamics of some

APPLICATION OF NMR TECHNIQUES IN STUDYING
THE DYNAMICS OF SOME POLYMERS
Mariana Butnaru1, R. Marcean2, O. Cozar3, I. Bratu4 and R. Fechete2
1
Weapons Factory, Cugir,. 21 Decembrie 1989 st, no. 1A,
R-15600 Cugir, Romania
2
Technical University Cluj-Napoca, Daicoviciu 1,
R-400020, Cluj-Napoca, Romania
3
Faculty of Physics, Babes-Bolyai University Cluj-Napoca, Cluj-Napoca,
Romania
4
National Institute for R&D of Isotopic and Molecular Technologies
R-400293, Cluj-Napoca, Romania
An important objective of polymer science is to establish a relationships between the microscopic structure or
molecular dynamics and the macroscopic properties of materials. This knowledge allows then the design of new
polymers with improved properties. By employing various NMR techniques it is possible to acquire information
on structure, morphology, and chain dynamics on the microscopic, mesoscopic and macroscopic scale.
Single-side NMR is particularly suitable for the measurements of the segmental motion in elastomers.
Whereas the segmental motions lead to liquid-like behavior, the presence of permanent or transient cross-links
leads to residual dipolar or quadrupolar couplings that are responsible for the solid-like properties1. In the last few
years, several NMR applications have been developed that operate in strongly inhomogeneous static and radio
frequency magnetic fields2,3,4. The so-called “NMR-MOUSE®“ (Nuclear Magnetic Resonance Mobile Universal
Surface Explorer), is a mobile instrument initially designed for analysis of polymer materials. It is portable and can
be carried to the object of interest.
Proton transverse nuclear magnetic relaxation times were investigated with the NMR-MOUSE® by
recording the CPMG decays for a series of natural rubber samples and subjected to some external aging factors.
Assuming a multi-exponential decay, the NMR signal was Laplace inverted using the well known UPEN
algorithm5. The resulted transverse relaxation time distributions can give us complex information related to the
polymer chain motions. We have found out that a common effect of all aging factors is to shift the T2 distribution to
larger times. This result can be correlated with a much faster motion probably due to breakage of some chemical or
physical topologically constrains. The samples were investigated in depth, entirely non-destructively, by placing
the NMR-MOUSE® in the spot to be measured. In this way the same sample can be again aged and then measured
using the NMR techniques or other like IR spectroscopy.
1
J.-P. Cohen Addad, Prog. NMR Spectrosc. 25, 1 (1993).
A. Guthhausen, G. Zimmer, P. Blümler, B. Blümich, Analysis of polymer materials by surface NMR via the
MOUSE, J. Magn. Reson. 130, 1-7, (1998).
3
K. Hailu, R. Fechete, D. E. Demco, B. Blümich, Segmental anisotropy in strained elastomers detected with a
portable NMR scanner, Solid State Nucl. Magn. Res. 22, 327-343, (2002).
4
M. Klein, R. Fechete, D.E. Demco, and B. Blümich, Self-Diffusion Measurements by Constant-Relaxations
Method in Strongly Inhomogeneous Magnetic Fields, J. Magn. Reson., 164 310-320 (2003).
5
G. C. Borgia, R. J. S. Brown, and P. Fantazzini, Uniform-Penalty Inversion of Multiexponential Decay Data, J.
Magn. Reson., 132, 65-77 (1998).
2
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NMR-MOUSE is a registered trademark of RWTH Aachen, Germany.