Reversible and irreversible structural changes of cellulose microfibrils in single cotton fibers during the drying...

This study investigates the structural evolution of cellulose microfibrils in single cotton fibers during the drying process using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) with synchrotron radiation. To examine reversible and irreversible changes, we systematically compared never-dried cotton (NDC) and rewetted cotton (RWC). Scattering profiles across a broad q-range revealed that NDC possesses a significantly thicker amorphous shell surrounding the crystalline core of cellulose microfibrils than RWC. Upon drying, both the crystallite size and crystallinity decreased; however, these changes were largely recovered upon rewetting. In contrast, the amorphous shell underwent irreversible densification and shrinkage. Based on the SAXS profiles and structural parameters derived from a core-shell-cylinder model, the drying process was categorized into three distinct stages. These findings emphasize the critical role of hydration history in determining the nanoscale architecture of cellulose microfibrils and provide new insights into the dynamic structural behavior of cellulose-based fibers.