Ramie, cellulose

The second choice is a simpler solution. According to Sarko and Muggli,66 all 39 observed reflections in the Valonia X-ray pattern are indexable by a two-chain triclinic unit cell with a = 9.41, b =8.15 and c = 10.34 A, a = 90°, 3 = 57.5°, and y = 96.2°. Ramie cellulose, on the other hand, is completely consistent with the two-chain monoclinic unit cell. Also, there are significant differences between their high-resolution solid-state l3C NMR spectra, indicating that Valonia and ramie celluloses, the two most crystalline forms, reflect two distinct families of biosynthesis. On this basis, the Valonia triclinic and the ramie monoclinic forms are classified69 as Ia and Ip, respectively. It has been shown from a systematic analysis of the NMR spectra by these authors, and from electron-dif-... 

Figure 1. X-ray diffraction pattern of ramie cellulose I. Fiber axis is vertical.

Figure 2. Two projections of the ramie cellulose I crystal structure on a-b plane (topT on b-c plane (bottom). Hydrogen atoms are omitted hydrofifeu bonds, ar who warfe dashed lines.

Using the two-chain unit-cell,3 with a = 0.817 nm, b = 0.785 nm, c = 1.034 nm, andy = 96.38°, the modified intensity-data of Mann and coworkers,37 and several residue-geometries, the structure of native ramie cellulose was refined. The resulting R factors were 15.8%, 18.5%, and 17.5% for, the antiparallel, parallel-up, and parallel-down models, respectively. A temperature factor of 0.23 nm2 was necessary in order to obtain a good fit with the observed data. It was suggested that the antiparallel packing of the chains cannot be discounted for cotton and ramie celluloses. 

Fig. 83. X-Ray diagrams (according to Miles and Craik [13]) (a) ramie cellulose, (b) ramie cellulose dinitrate, (c) ramie cellulose trinitrate.

Bleached ramie-cellulose Unbleached ramie-cellulose — ... 

Figure 4. Smoothed equatorial trace for Ramie (Cellulose I) fibers with resolved 101,101, and 002 profiles, and best-fit background...

Resolved parameters for Ramie (Cellulose i) and Fortisan (Cellulose II)... 

Figure 1. Water vapor adsorption kinetics of ammonia-treated ramie cellulose ( first exposure to water vapor after drying from ammonia O repeated exposures thereafter to water vapor after drying from 6% moisture content) (36)...

Woodcock C, Sarko A (1980) Packing analysis of carbohydrates and polysaccharides, II. Molecular and crystal structure of native ramie cellulose. Macromolecules 13 1183-1187... 

Lattice images of algal, bacterial, and ramie cellulose have been obtained. These images show the individual molecular chains and the sizes of microfibrils, which vary in size and shape according to the source of cellulose [242,243]. There is also some variation within a given source. For example, microfibrils of Valonia ranged from 150 to 250 A (15 to 25 nm). 

Nishiyama Y, Sugiyama 1, Chanzy H and Langan P (2003) Crystal structure and hydrogenbonding system in cellulose la from synchrotron x-ray and neutron fiber diffraction. Journal of the American Chemical Society, 125(47) 14300-6 Nishiyama Y, Kim U-1, Kim D-Y, Katsumata KS, May RP and Langan P (2003) Periodic disorder along ramie cellulose microfibrils. Biomacromolecules, 4 1013-7 NIST (1995) Voluntary product standard PS 1-95. Construction and industrial plywood. US Department of Commerce, National Institute of Standards and Technology, Gaithersburg, Maryland... 

Fig, 1.—Set of F our Diagrams from Ramie and Rayon Fibers, Corresponding to the Four Principal Polymorphs of Cellulose. ((A) Cellulose I (native) from purified ramie fibers, (B) Cellulose II (mercerized or regenerated) from Fortisan fibers, (C) Cellulose III (ammonia) from ramie fibers treated with ethylamine, and (D) Cellulose IV (high temperature) from fibers of ramie cellulose III treated with gIy< rol at 280 .]... 

Figure 1 shows a 50 MHz CP/MAS C NMR spectrum of ramie cellulose and a stick-type nmr spectrum of low molecular weight cellulose( DP <10) In deuterated dimethyl sulfoxide solution(DMSO) (8 ) (The broken and solid lines In the CP/MAS spectrum will be explained below.). As already reported(9,10), the assignments for the Cl, C4 and C6 carbons are relatively easy, based on analogies with the solution state spectrum. However, It should be noted that these resonance lines shift downfleld by 2.3-9.6 ppm In the solid state compared to the solution state. The cause of such large downfleld shlfts(to be explained In the next section) Is attributed to the different conformations about the P-l,4-glycosldlc linkage and the exo-cyclic C5-C6 bond in which these carbons are Involved. 

Selection of Ramie Cellulose for Study. Ramie cellulose was selected for study because it is highly oriented and fairly... 

Monomeric Geometry. Previous work (21) showed that the overall conclusions are not substantially affected by small differences In coordinates for the glucose ring used in the Starting model. We have reexamined this point since the WS and RMF data sets have become available for ramie cellulose, along with the WS monomeric geometry that was internally adjusted to best agree with the WS diffraction and stereochemical analysis of ramie. 

FRENCH ETAL. X-ray Diffraction Studies of Ramie Cellulose I... 

Figure 7 shows the spectra of the crystalline components of cotton celluloses with the water contents of 0% and 161%, which were obtained by the method described in the previous section(4). The multiplet of the Cl resonance is clearly seen in these spectra in the dry state two nonequivalent lines seem to constitute this resonance but they split into one doublet and one small singlet centered at the doublet in the hydrated form. Moreover, C4 and C6 resonances tend to split into a triplet and a doublet, respectively. Almost the same spectra were obtained for ramie cellulose in both dry and hydrated forms. 

Cellulose polymorphy was studied by comparing the spectra of Valonia, ramie, and mercerized ramie. It appears that the conformation of the cellulose backbone is the same in Valonia and ramie celluloses, but that the hydrogen bonding patterns are different. Mercerized cellulose and native celluloses differ in both their backbone conformations and hydrogen bonding patterns. 

Polymorphy. Cellulose polymorphy within the cellulose I family was studied by comparing the Raman spectra of VaIonia and ramie cellulose. Solid state NMR spectra indicate that the I, form predominates in Valonia while the Ig form predominates in ramie (17-18). 

It was observed In earlier studies of controlled alkall-mercerlzatlon of ramie cellulose that the crystal structure of native cellulose Is transformed to cellulose II through a series of crystalline alkali-cellulose complexes (1,2). The relationships between these "Na-celluloses" and their pathways of transformation are Illustrated In Fig. 1. It has further been observed that all of the transformations are crystal-to-crystal phase changes, not Involving Intermediate amorphous phases. All of the experimental evidence has suggested... 

We are investigating the structures of these complexes using the refinement methods applied to celluloses I and II, as described above. In the next sections we describe the results of these analyses for three complexes ramie cellulose I-ethylene-diamlne [(28), ramie cellulose I-l,3-propanediamine (29). and Fortisan cellulose Il-hydrazine A, which are the most crystalline complexes prepared to date. 

---