NMR Methods for Characterization of Synthetic and Natural Polymers
Chapter 8: Rubber-state NMR Spectroscopy
Published:29 Jul 2019
Special Collection: 2019 ebook collectionSeries: New Developments in NMR
S. Kawahara, Y. Yamamoto, and T. Saito, in NMR Methods for Characterization of Synthetic and Natural Polymers, ed. R. Zhang, T. Miyoshi, and P. Sun, The Royal Society of Chemistry, 2019, ch. 8, pp. 156-173.
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Vulcanized rubbers, i.e., vulcanized natural rubber and vulcanized chloroprene rubber, were characterized by rubber-state NMR spectroscopy. High resolution 1H and 13C-NMR spectra were accomplished for the vulcanized rubbers due to fast magic angle spinning. The correlation between 1H and 13C of the vulcanized rubbers was investigated by one- and two-dimensional measurements. As for vulcanized natural rubber, the signals, appearing between 40 and 60 ppm, were well assigned by rubber-state NMR spectroscopy; for instance, the signal at 40 ppm was assigned to C1 of trans-1,4-isoprene units, while the signal at 44 ppm was assigned to secondary carbons linking to an S atom and signals at 58 ppm were assigned to tertiary and quaternary carbons linking to S atoms. In contrast, for chloroprene rubber, a 1H-signal at 0.9 ppm, appearing after vulcanization, was correlated to a 13C-signal at 14.5 ppm and the 1H signal at 1.3 ppm was correlated to a 13C-signal at 22.5, 29.5, and 31.8 ppm. A constitutional unit, i.e., CH3–CH2–CH2–S–R was found for vulcanized chloroprene rubber by rubber-state NMR spectroscopy.