Cellulose schematic models

Schematic model of the cellulose synthase complex crystalline cellulose I emerges from the rosette terminal complex, which is embedded in the plasma membrane. View from the top (above) and the side (below). (Adopted from Perez and Mazeau [42] and from Horii [40])...

Figure 2.4. (a) Schematic model of a microfibril with metastable (LHS) and modified (RHS) surface, (b) Alternate twisting of surface glucosyl units by 30 results in less strain, (c) CP-MAS spectra for flax (30% surface chains) and celery cellulose (60% surface chains) can be split into spectra of surface (S) and interior (I) chains (Vietor et al., 2002). 

T,he chemical structure of cellulose chains was established by Haworth and Hibbert more than 40 years ago. Native cellulose occurs in solid state and in partly crystalline form. A schematic model for the native cellulose lattice was worked out about 1930 by Meyer, Mark, and Misch. The basic morphology of native cellulose could not be resolved, however, before electron microscopy with high resolution was developed and applied. During the last two decades, it has been amply shown and is now generally accepted that native cellulose basically is composed of microfibrils of a width 100 A. or less as was reviewed in 1956 (12). 

Fig. 5 Schematic model of (a) palmitoyl cellulose Langmuir-Blodgett films and (b) stearic acid Langmuir-Blodgett films on the ITO substrate.

Fig.5 shows schematic models of PC-LB film and SA-LB film on the ITO substrate. Both structures of PC-LB film and SA-LB film are regular in the direction parallel to film surface. However, the structure of SA-LB film in the direction perpendicular to the film surface seems to be irregularly aligned. In PC-LB film, the distance between palmitoyl chains keep some same distance. The conformation of palmitoyl chains is most probably determined due to cellulose main chains. 

Figure 7 Schematic model of self-assembling process of synthetic cellulose on the surface of enzyme associations diffusion of monomers to active sites of the enzyme aggregate (a), which synthesizes cellulose molecules (b) and self-assembles them In situ Into dendritic cellulose aggregates with Dm = 2.1 and Ds = 2.3 in the reaction medium around the enzyme aggregates (c) The cellulose aggregates eventually growing into the dome (d). The cellulose aggregate surrounding the enzyme association has enough free space for diffusion of monomers from the reaction medium into the active sites and for diffusion of terminated polymers from the active sites Into the reaction medium as shown in part (e) and discussed in Section 2.13.3.2. From Tanaka, H. Koizumi, S. Hashimoto, T. et al. Macromolecules 2007, 40, 6304-6315. ...

Figure 9 Schematic structure models of native cellulose and cupra rayon fibers-...

Figure 12 Schematic structural models of native and regenerated cellulose samples.

In many instances polymers are in contact with liquids that penetrate their stmcture. This process is usually accelerated when the Uquid has a plasticizing effect on polymer. The permeation of a solvent through a pervaporation membrane is a special case of such a situation. Figure 11.2 shows a schematic transport model of a mixture of methanol, MeOH, and methyl tert-butyl ether, MTBE, through cellulose triacetate pervaporation membrane. " ... 

Figure 6. Schematic representation of the ceUuiose -p model, units are in angstroms. The dimensions of the cellulose unit cell are displayed in two views top (or bottom) view (left) show the distance along the cellulosic axle (10.511 A) and the distance between cellulose chains at the same lattice (8.240 A), meanwhile the side view displays the thickness of all three lattices (8.189 A) of the cellulose unit cell.

In light of the mentioned facts, we designed an experimental setup, which serves as the platform for such testing. To be reproducible, effective and to allow proper evaluation, it had to be simplified as far as possible. It consists of a model surface (atomically flat silicon wafer), two different pol)nner molecules (carboxy methyl cellulose and amylose) and solutions exhibiting different pHs and ionic strengths. The setup is schematically depicted in Figure 12. 

Figure 9.1. A. Fringe-fibril model of cellulose after Hearle [4] see also Zugenmaier [1], The right figure B. shows a schematic of a macro-fibril as existing in plant cells begin a composite of micro-fibrils. These consist of elementary fibrils which are made of 30-40 polymeric linear cellulose chains (picture based on the botany visual resource library [5]). The picture in figure A. is observed in crystalline cellulose, grown either artificially as for instance in textile fibers [1] or can be thought to mimic the structure of elementary fibrils.

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