Hierarchical porous structures in cellulose: NMR relaxometry approach

Hierarchical porous structures in cellulose materials are important for the dissolution, properties and applications of cellulose materials. Methods for characterizing the hierarchical porous structures in cellulose materials without changing its original state are still limited. In this work, we introduced nuclear magnetic resonance (NMR) relaxometry for characterizing the hierarchical porous structures in cotton fibers without modifying their structure during sample preparation. By this method, the changes of the porous structures in cotton samples were characterized. It was found that soaking cellulose in water and stewing cellulose in N,N-dimethylacetamide at high temperature could efficiently improve the accessibility of cellulose samples to the solvent molecules and expand the Amorphous Region in cellulose. The method provided in this work can be used for the evaluation of the hierarchical porous structures of cellulose materials without additional modified information, which is helpful to the utilization of cellulose in various fields.