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Structural changes of cellulose determined by dissolution in aqueous alkali solution

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Ciolacu, D; Popa, VI

Editorial: CELLULOSE CHEMISTRY AND TECHNOLOGY, 39 (3-4), p.179-188, 2005.

Rezumat:

This study was focused on the changes in the fine structure of cellulose
samples of different origin during treatment with sodium hydroxide solution. Three types of
cellulose, microcrystalline cellulose, spruce dissolving pulp and powder linters cellulose were
alkalized with solution of sodium hydroxide of different concentrations, at -30°C. After
alkalization the samples were defrozed, washed until neutral and dried in air. The structural
changes of the samples were evidenced by X-ray diffraction. A particular attention was given
to the influence of treatment with aqueous NaOH solutions on the crystallinity and
orientations of the chains in the cellulose samples. It was observed that an increasing
concentration of alkali (from 5 to 18% NaOH) determined a decrease in the degree of
crystallinity of cellulose samples, as an effect of the molecular degradation of cellulose. Also,
it was established a direct correlation between decrease in crystallinity and H-bond splitting.
The structural modifications were determined by splitting and new formation of inter- and
intramolecular H-bonds. The conformational modification in the cellulose molecules is the
result of the interaction between inter- and intramolecular H-bonds during chain rotation.

Cuvinte cheie: Cellulose I/II transition, X-ray diffraction, Crystallinity, Crystallite size