APPLICATION OF NMR TECHNIQUES IN STUDYING
THE DYNAMICS OF SOME POLYMERS

Mariana Butnaru1, R. Marcean2, O. Cozar3, I. Bratu4 and R. Fechete2

1Weapons Factory,  Cugir,.  21 Decembrie  1989 st,  no. 1A, 
R-15600 Cugir,  Romania
2Technical University Cluj-Napoca, Daicoviciu 1,
 R-400020, Cluj-Napoca, Romania
3Faculty of Physics, Babes-Bolyai University Cluj-Napoca, Cluj-Napoca, Romania
4National 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.

1J.-P. Cohen Addad, Prog. NMR Spectrosc. 25, 1 (1993).
2A. Guthhausen, G. Zimmer, P. Blümler, B. Blümich, Analysis of polymer materials by surface NMR via the MOUSE, J. Magn. Reson. 130, 1-7, (1998).
3K. 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).
4M. 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).
5G. C. Borgia, R. J. S. Brown, and P. Fantazzini, Uniform-Penalty Inversion of Multiexponential Decay Data, J. Magn. Reson., 132, 65-77 (1998).

®NMR-MOUSE is a registered trademark of RWTH Aachen, Germany.