Microgels and ionic associations in solutions of cellulose diacetate |
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Authors: | E. Fleury J. Dubois C. Léonard J. P. Joseleau H. Chanzy |
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Affiliation: | (1) Rhône Poulenc Recherches, B.P. 62, 69192 Saint Fons Cedex, France;(2) Centre de Recherches sur les Macromolécules Végétales CNRS, B.P. 53X, 38041 Grenoble Cedex, France;(3) The Joseph Fourier University of Grenoble, France |
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Abstract: | Solutions of cellulose diacetate (CDA) from two sources (cotton linters and wood pulp Floranier) were analysed in various solvents by size exclusion chromatography (SEC). Without special precautions, the SEC chromatograms presented three peaks — or prehumps — before the main polymer peak. The first prehump which could be eliminated by ultracentrifugation corresponded to microgels whose sugar composition was determined. These microgels were also investigated by electron microscopy, X-ray and electron diffraction analysis. They corresponded mainly to cellulose triacetate (CTA-II) in the case of CDA from cotton linters and a mixture of CTA-II and xylan diacetate (XDA) in the case of CDA from the wood pulp Floranier. The second and third prehumps could be attributed to ionic effects corresponding to the association of remaining sulfate groups on the CDA molecules with residual calcium. It was found that these ionic effects could be eliminated by the addition of LiBr or LiCl to the elution solvents. This led to chromatograms devoid of prehumps.Presented in part at the Cellulose '91 meeting in New Orleans. |
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Keywords: | cellulose diacetate wood pulp hemicelluloses microgels size exclusion chromatography calcium interaction prehumps |
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