The nature of accessible surfaces in the microstructure of cotton cellulose

The accessible regions in cotton cellulose were tagged by the introduction of diethyl-aminoethyl (DEAE) substituents at DS = 0.034 without other substantial changes in structure. Evidence from rates of hydrolysis of this DEAE cotton to hydrocelluloses and from the composition and structure of the solubilized and insoluble fractions provides the basis for considerable detail regarding two types of accessible regions in the cotton fiber; these are identified as accessible surfaces of elementary fibrils. One type of accessible surface is characterized by molecular chain segments which are distorted and disordered by tilt/twist strain that is concentrated in this segment of the elementary fibril; the second type of accessible surface is characterized by a relatively high degree of order which reflects the high level of crystallinity within the interior of this unstrained segment of the elementary fibril. Substantial differences between these accessible surfaces are discussed. It is estimated that chain segments on accessible surfaces of the first type are substantially disordered, i.e., approximately 60–90% of the D-glucopyranosyl units are dislocated from positions of perfect crystalline order. Accessible surfaces of the second type are quite highly ordered, i.e., only 5–30% of the D-glucopyranosyl units dislocated.