Determination of the Structure of Cellulose II

Abstract

The structure of regenerated cellulose is shown by x-ray diffraction to be comprised of an array of antiparallel chain molecules. The determination was based on the intensity data from rayon fibers and utilized rigid-body least-squares refinement techniques. The unit cell is monoclinic with space group P2(1) and dimensions a = 8.01 A, b = 9.04 A, c = 10.36 A (fiber axis), and gamma = 117.1 degrees. Models containing chains with the same sense (parallel) or alternating sense (antiparallel) were refined against the intensity data. The only acceptable model contains antiparallel chains. The -CH2OH groups of the corner chain are oriented near to the gt position while those of the center chain are near to the tg position. Both chains possess an O3-H-O5' intramolecular hydrogen bond, and the center chain also has an O2'-H-O6 intramolecular bond. Intermolecular hydrogen bonding occurs along the 020 planes (o6-h-o2 bonds for the corner chains and O6-H-O3 bonds for the center chains) and also along the 110 planes with a hydrogen bond between the O2-H of the corner chain and the O2' of the center chain. This center-corner chain hydrogen bonding is a major difference between the native and regenerated structures and may account for the stability of the latter form.

Fourier Transform Infrared Spectroscopy for Natural Fibres

“…Table 3. Absorption wavenumber between the real and synthesized IR spectra of amorphous cellulose [43,47] The traditional two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) regions. A parameter termed the crystallinity index (CI) has been used to describe the relative amount of crystalline material in cellulose.…”

Effect of Polymorphism on the Particle and Compaction Properties of Microcrystalline Cellulose

“…It is obtained from wood pulp by treatment with dilute strong mineral acids (HCl, H2SO4, HNO3) at boiling temperatures until the degree of polymerization levels-off [7,8]. The acid hydrolyzes the less ordered regions of the polymer chains, leaving the crystalline regions intact.…”

A review on systematic study of cellulose

“…For cellulose I, a tg orientation gave the best fit (Gardner and Blackwell, 1974a) with the R value for tg, gt and gg models being 0.242, 0.292 and 0.349, respectively. For cellulose II, both regenerated (Buleon and Chanzy, 1978) and mercerized (Kolpak and Blackwell, 1976) forms were reported to have a gt conformation throughout the cellulose chain at the corner of the unit cell, but a tg arrangement for the centre chain. However, some rotation about the suggested minimum orientations (tg, gt and gg) was accepted as being possible.…”

“…The value of ã is greater for mercerized specimens than for most regenerated samples (Wellard, 1954). Also, as the degree of purity of samples used has been shown to be relevant, it should be noted that regeneration gives a higher level of conversion of cellulose I to cellulose II (Kolpak and Blackwell, 1976). Nyburg (1961) reported one example of naturally occurring cellulose II, in the genus Halicystis.…”

“…Kuga et al (1993) reported a mutant strain of Acetobacter xylinum as containing native folded-chain cellulose II. Another commonly studied aspect of cellulose II is the direction of the chains in the unit cell and the most prevalent view is that the two cellulose chains lie antiparallel to one another (Sarko and Muggli, 1974;Kolpak and Blackwell, 1976;Stipanovic and Sarko, 1976).…”