Nuclear Magnetic Resonance Studies of Molecular Motion in Natural Rubber

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Abstract
Nuclear magnetic resonance measurements have been made on natural rubber to examine how frequency, temperature, and crystallinity influence the nuclear relaxation. Molecular motions were studied by observing NMR linewidths and spin-lattice relaxation times at temperatures between −100° and 100°C, and at radio frequencies between 2 and 60 Mc. The influence of crystallinity was seen in measurements on stark rubber. The relation between frequency and temperature in the spin-lattice relaxation process is examined in terms of the Arrhenius equation and the WLF expression. The importance of using frequency as a variable in NMR studies of molecular motion is stressed.