Synchrotron X-ray fiber diffraction study on the thermal expansion behavior of cellulose crystals in tension wood of Japanese poplar in the low-temperature region

The thermal expansion behavior of tension wood cellulose obtained from Populus maximowiczii A. Henry was investigated by synchrotron X-ray fiber diffraction at temperatures ranging from 100 to 300 K. Three equatorial and one meridional d -spacings indexed as , 110, 200, and 004 showed a gradual linear increase with increasing temperature. Unit-cell parameters calculated from the changes in these d -spacings showed anisotropic thermal expansion behavior in the three axial directions related to the crystal structure and hydrogen-bonding system of cellulose I β . The linear thermal expansion coefficients (TECs) of the a -, b -, and c -axes were: α a =5.2×10 -5 K -1 , α b =2.1×10 -5 K -1 , and α c =0.4×10 -5 K -1 , respectively. The volume TEC was β =7.8×10 -5 K -1 , which was approximately 70% of previously reported values in the high-temperature region from room temperature to 250°C.