Investigation of the change in the fine structure of Valonia cellulose upon wet heating and mercerization

A Valonia cellulose (NV), a cellulose II derived from NV by mercerization (MV), and a cast cellulose II film (F) were deuterated repeatedly (wetting-drying cycle) in vapor phase at 25°C; the integrated deuteration time amounts to 5 × 10⁵ min. A region C, which cannot be attacked by the exchange reaction, exists in NV and MV, amounting to 80 and 18% in the respective samples. In the case of F, it could not be determined exactly due to the too large scattering of the data. On heating in liquid D₂O for 5 or 10 min., OD groups develop within C above 190 and 170°C in NV and MV, respectively. Above 190°C. the exchange is larger in NV than in MV. These OD groups within the pre-existing crystallites begin to disappear after treating with NaOH solution at the concentration at which cellulose begins to be converted to alkali cellulose I. The resistant OD groups developed within the amorphous and intermediate regions are rehydrogenated by the more dilute alkaline solutions.