Revealing dynamic crystalline structure development in cotton fibers using cellulose-specific Rietveld refinement

The crystalline structure of cotton fibers governs their mechanical and physicochemical properties, yet limitations in reliable characterization methods have hindered detailed insight into their structural development. In this study, a cellulose-specific Rietveld refinement approach was applied to elucidate crystalline structure development in cotton fibers. Using a four-step sequential refinement procedure, X-ray diffraction data collected from fibers between 20 and 66 days post‑anthesis (DPA) were analyzed. The calculated diffraction patterns showed excellent agreement with the measured patterns across all samples, yielding low figures of merit. Refined structural parameters—including the a -axis, b -axis, γ -angle, crystallite size, crystalline volume fraction, and March-Dollase preferred orientation coefficient along the [001] direction—exhibited coordinated, multi-step changes with DPA. These variation patterns resolved five mechanistically distinct stages by revealing two-step secondary cell wall thickening and maturation as well as a late stage of crystallite coalescence and lateral growth. Full-pattern Rietveld analysis demonstrates highly sensitivity to dynamic changes in crystalline structure and provides a quantitative approach to resolving structural development in cellulose fibers.