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
Seiichi Kawahara, Yoshimasa Yamamoto, Takayuki Saito, 2019. "Rubber-state NMR Spectroscopy", NMR Methods for Characterization of Synthetic and Natural Polymers, Rongchun Zhang, Toshikazu Miyoshi, Pingchuan Sun
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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.