In situ SAXS analysis of the water effects on the thickness evolution of nanocellulose within bamboo fiber

To investigate the thickness evolution of nanocellulose in water, in situ SAXS (small angle X-ray scattering) was used to characterize bamboo fibers. The thickness of nanocellulose was calculated by ln I(q)−q² curve and the results indicated that the thickness of nanocellulose decreased (from 13.38 ± 2.358 nm to 8.77 ± 0.98 nm) in the first 6 h, then stabilized at 8 nm in the range of 9–19 h after soaking in water. Additionally, the internal pores of bamboo changed, with the macropores decreasing and tiny pores increasing, respectively. In particular, the thickness of the crystals in nanocellulose decreased which might be attributed to the expansion and more disordered amorphous zone in lignin and hemicellulose under the influence of water. As the mechanical properties of bamboo increased apparently with the increased water content, this study can promote a better understanding of the water effects on the mechanical behaviors and toughening mechanisms within natural cellulose fibers.