An infrared spectroscopic investigation of the hydration of cellulose

Abstract

Absorption spectra of water absorbed by cellulose at different relative humidities have been obtained by the differential recording method, and interpreted. It is shown that in sorption of the first portions of moisture the water molecules become hydrogen bonded to the cellulose hydroxyl groups, which mainly display proton donor properties. The hydrogen bridges formed by the OH groups of the water molecules differ substantially in strength, which results in loss of the symmetry of the watermolecules. In subsequent hydration hydrate structures are formed on the water molecules adsorbed previously, and these structures appear at lower degrees of humidity in native cellulose than in mercerized cellulose. It was found spectroscopically that at high relative humidities (>50%), hydration causes breakdown of the hydrogen bonds between the hydroxyl groups of the polymer. This occurs more extensively in mercerized cellulose than in native cellulose. There is an optimal relative humidity (50–70%) at which the maximal degree of ordering of the cellulose structure occurs.