Deconstruction of H-bonding and crystallite in directly prepared cellulose nanofibrils after autohydrolysis of eucalyptus

In this study, cellulose nanofibrils (CNFs) were directly prepared after autohydrolysis of eucalyptus raw materials. The effect of different autohydrolysis times on the hydrogen bond structure, micro-structure and properties of CNFs were analyzed by FTIR peak fitting, two-dimensional infrared, TGA, TEM and X-ray diffractometer. The results showed that the autohydrolysis treatments could obviously lead to the sequence of hydrogen bond changes in CNFs as follows: v (weak hydrogen bond) > v (free hydroxyl) > v (O(3)H.O(5)) > v (O(2)H.O(6)) >  v (O(6)H.O(3′)), and further impact in crystallite size of CNFs. With the increase of the autohydrolysis strength, the crystallite size of CNFs on the 1 1 ¯ 0 crystal plane could be reduced by up to 26%, but the crystallite size on the 110 crystal plane and the 200 crystal plane increased by 24.5% and 22.6%, respectively. These microstructure changes finally increased the crystallinity index of CNFs, and then resulted in their high thermal stability.