Journal
JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
Volume 21, Issue 1, Pages 71-77Publisher
SOC BRASILEIRA QUIMICA
DOI: 10.1590/S0103-50532010000100012
Keywords
cellulose aggregation; cellulose acetylation; degree of cellulose acetate substitution; LiCl/DMAc
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Funding
- FAPESP (State of Sao Paulo Research Foundation)
- CNPq (National Council for Scientific and Technological Research)
- INCT-Catalise
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We report here on some aspects of the acetylation in LiCl/N,N-dimethylacetamide, DMAc, of untreated and mercerized sisal cellulose, hereafter designated as sisal and M-sisal, respectively. Fiber mercerization by NaOH solution has resulted in the following changes: 29.9% decrease in the index of crystallinity; 16.2% decrease in the degree of polymerization and 9.3% increase in a-cellulose content. A light scattering study of solutions of sisal, M-sisal, microcrystalline and cotton celluloses in LiCl/DMAc has shown that they are present as aggregates, with (an apparent) average aggregation numbers of 5.2, 3.2, 9.8, and 35.3, respectively. The presence of these aggregates affects the accessibility of cellulose during its functionalization. A study of the evolution of the degree of substitution, DS, of cellulose acetate as a function of reaction time showed an increase up to 5 h, followed by a decrease at 7 h. Possible reasons for this decrease are discussed. As expected, M-sisal gave a higher DS that its untreated counterpart.
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