HYDROGEN EXCHANGE BETWEEN CELLULOSE AND WATER: I. MEASUREMENT OF ACCESSIBILITY

Abstract

Estimates of the extent of the hydrogen exchange reaction between cellulose and water vapor determined by an improved method using tritiated water and by the use of heavy water were usually in good agreement. With certain samples, surface roughness had a small effect upon the measurement of tritium radioactivity in cellulose.The accessibility or limiting extent of the exchange increased slightly with relative humidity in the range 20 to 100% and was attributed to the reduction of crystalline order reported recently in similar experiments.In contrast to cellulose whose accessibility corresponds approximately to the amorphous fraction, a partially crystalline amylose was 100% accessible while an amorphous xylan was 52% accessible, indicating that in these substances the accessibility and the fraction of amorphous material are not identical.