The degree of cellulose I crystallinity in cellulose rich samples isolated from different plants and organisms can be determined by CP/MAS 13C-NMR. IR-spectroscopy, Raman spectroscopy, and WAXS/XRD are methods that also can be used to determine cellulose crystallinity. All methods for cellulose crystallinity determinations are associated with complications. A common complication is found in the lack of absolute agreement between measurements performed by different methods, effectively meaning that cross-verification of results seldom is possible. Cellulose crystallinity determinations made with CP/MAS 13C-NMR has the advantage that it can be performed without the need for calibration curves or reference substances for e.g. amorphous cellulose, and NMR line-shape theory can be an aid in the interpretation of CP/MAS 13C-NMR cellulose spectra. However, CP/MAS 13C-NMR crystallinity determinations rests upon assumptions about the cellulose supramolecular structure, assumptions that still are debated within the scientific community. The theoretical assumptions for making cellulose crystallinity determinations using CP/MAS 13C-NMR will be discussed and compared with other techniques. Complications arising with the NMR methods when applied to samples contaminated by other biopolymers will be discussed.

Determining cellulose I crystallinity by CP/MAS 13C-NMR

2019 Spring National Meeting

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