The structural elucidation of cellulose and its derivatives, especially for those with relatively low crystallinities or in native cell walls, has long been limited by the insufficient resolution of conventional analytical methods. Here, we present a novel method for investigating the molecular structure of unlabeled cotton cellulose by combining natural-abundance <sup>13</sup>C-<sup>13</sup>C 2D correlation solid-state NMR spectroscopy, as enabled by the sensitivity-enhancing technique of dynamic nuclear polarization (DNP), with statistical analysis of the observed and literature-reported chemical shifts. The atomic resolution allows us to monitor the loss of Iα and Iβ allomorphs and the generation of a novel structure during ball-milling, which reveals the importance of large crystallite size for maintaining the Iα and Iβ model structures. Partial order has been identified in the “disordered” domains, as evidenced by a discrete distribution of well-resolved peaks. These results provide heretofore unavailable high-resolution insights into cotton cellulose but also presents a widely applicable strategy for analyzing the structure of cellulose-rich materials without isotope-labeling. In addition, the development of a polysaccharide solid-state NMR database further allows large-data analysis of the atomic structure of unlabeled cellulose and benefits the community of cellulose research.

Atomic Resolution of Cellulose Structure Enabled by Dynamic Nuclear Polarization Solid-State NMR and Database Development

2019 Spring National Meeting

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