Characterization of Natural Rubber End Groups Using High-Sensitivity NMR

摘要

The chemical structures of natural rubber (NR) end groups are investigated by combining chemical treatments and sensitivity-enhanced modern nuclear magnetic resonance (NMR) spectroscopy instruments equipped with a cryoprobe. The obtained 1H NMR spectrum of the α-end has improved signal intensity than that obtained with conventional instruments, as well as clearer splitting patterns due to the higher resolution given by the higher magnetic field. Through the ~1H/~(13)C 2D NMR experiments and the 1D NMR spectra of the model compounds, four types of α-end structures are suggested. Two structures among them are considered related to those of mushroom-derived NR found in the literature, whereas the others are not recognized to date. Solidstate ~(31)P cross-polarization/magic angle spinning (CP/MAS) NMR is also carried out to detect the phosphate group around the terminal.