The Structure of Cellulose by Conformational Analysis. 2. The Cellulose Polymer Chain

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Abstract
Conformational analysis studies on the tertiary structure of cellotetraose, methyl-.beta.-cellotetraoside, and single cellulose chains were carried out by using calculation of van der Waal, H-bond, electrostatic, and torsional energy interactions between the atoms and molecular groups in both the skeleton and side chains of the cellulose polymer. The .beta.-glucosidic linkages connecting 2 monomers were proved to be in different .PHI..degree., .PSI..degree.) conformations, with different rotational energy barriers and with different H-bond shielding than the .beta.-glucosidic linkages within the cellobiose-like monomers. This confirms the anomalies in the hydrolytic behavior of cellulose reported by other authors. H-bonds and van der Waal''s forces were the predominant factors in the fixation of the most favored conformations. The role of H-bonds is again predominant. Single cellulose chains, not in a crystalline network, were found to be in extended helicoidal conformations. These types of conformation are most probable for cellulose in solution and for the cellulose amorphous regions. The conformations most likely to form the crystalline and amorphous regions of native wood cellulose have been indicated pending further study of the crystalline network. Only 2 models for wood cellulose, namely the "2-fold" helix and oscillating "2-fold" helix symmetry, appear likely to satisfy the properties of cellulose and the energy balance deduced for single chains.

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