Structural Change of Cellulose by Grinding and Its Dissolution in Aqueous NaOH Solution

Publication Reference: 
31-12
Author Last Name: 
Saito
Authors: 
Fumio Saito, Qiwu Zhang, Junya Kano and Koichi Mizukami
Report Type: 
ARR
Research Area: 
Size Reduction
Publication Year: 
2002
Publication Month: 
12
Country: 
Japan

Present annual report-2002 described results on the second year’s work after renewal of the first period (1998-2000) in the theme of “Mechanochemistry of Materials” approved by the IFPRI organization. The work focuses on structural change of cellulose by grinding and its dissolution in aqueous NaOH solution. Under this concept, the contractor (F. Saito) and his group have extensively investigated the mechanochemical (MC) work from both viewpoints of experimental and computer chemistry. Several characterizations such X-ray diffraction (XRD), TG-DTA and FT-IR analyses have been conducted for the ground sample, and regarding the XRD analysis, the grinding enables us to transform the structure of cellulose into disordered system like an amorphous state in the prolonged grinding. The TG-DTA and FT-IR spectra are almost the same as those in the initial stage, the dissolution of cellulose in the aqueous NaOH solution is however improved. Cellulose has donor and accepter composing hydrogen bonds in the molecule, and the bond is strong relatively in comparison with other similar structured materials such as glucose and lactose. In spite of this, improvement in the dissolution of cellulose in the solution may be due to the disturbance of internal molecules of hydrogen bonds and their rupturing. This is followed by the investigation on the computer chemistry work, which has shown the weakest part of the chain structure of cellulose in the all, so that the rupture may be initiated to break at C-O bonds in the molecule. Of course, other parts of the structure are also subjected to damage by the grinding, however, the unit cell like cellubiose may remain unaltered in the prolonged grinding. This may be confirmed from the results of TG-DTA and FT-IR analyses. The substance re-crystallized from the solution may be cellulose, of which structure may have slightly different from the initial one. Grinding the cellulose results in the agglomeration of particles, of which sizes are not significantly changed. These facts suggest the suitable application of the ground cellulose to food and pharmaceutical fields.

This work has been presented at the IFPRI AGM 2002 held at Sendai, Japan in 15-18, July 2002. At this moment, it is still unknown, but “mechanochemistry of cellulose” has a potential to extend to food and pharmaceutical fields, because the ground sample of cellulose is, in fact, still maintaining the same unit cell even in the prolonged grinding stage, changing its part of the structure, correspondingly its physico-chemical properties such as solubility. During the course of this investigation, the evidence may be initiation to start an application of mechanochemistry to food and drugs field by modification of morphology and structure of such products. This is also a great expectation of this series of work to come.