CP/MAS Carbon-13 NMR Study of Spin Relaxation Phenomena of Cellulose Containing Crystalline and Noncrystalline Components

Cross-polarization, 13C rotating frame spin-lattice relaxation and C laboratory frame spin-lattice relaxation processes have been studied for different cellulose samples by CP/MAS 13C NMR spectroscopy. It was found that the CP process can be described by a simple thermodynamic model and relative intensities of the respective resonance lines are consistent with the atomic ratios for the spectra obtained at a contact time of about 1 ms. The observed rotating frame spin-lattice relaxation times TC 10 were dominantly dependent on the time constant TD CH by which 13C nuclei were coupled to the 1H dipolar spin system. It was, therefore, impossible to obtain information about molecular