FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for esterification of cellulose: I. Formation of anhydrides without a catalyst |
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Authors: | Xiaohong Gu Charles Q Yang |
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Institution: | (1) Department of Textiles, Merchandising and Interiors, The University of Georgia, 30602 Athens, GA, U.S.A. |
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Abstract: | In recent years, extensive efforts have been made to find nonformaldehyde durable press finishes to replace the traditional
formaldehyde-based reagents for producing wrinkle-free cotton fabrics. 1,2,3,4-butanetetracarboxylic acid (BTCA) has been
the most effective nonformaldehyde crosslinking agent. Our previous research has indicated that a polycarboxylic acid esterifies
cellulose in two steps: the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl
groups, and the reaction between cellulose and the anhydride intermediate to form an ester linkage. In this research, we used
Fourier transform infrared and Fourier transform Raman spectroscopy to study the formation of cyclic anhydride intermediates
by BTCA and other polycarboxylic acids without the presence of a catalyst. We found that BTCA and other polycarboxylic acids
in a crystalline state start to form 5-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of
their melting points with the exception of bifunctional acids, which form cyclic anhydrides at temperatures much higher than
their melting points. Intermolecular hydrogen bonding between carboxylic acid groups prevents the formation of the cyclic
anhydride intermediates at lower temperatures. We also found that polycarboxylic acids in an amorphous state form cyclic anhydrides
at much lower temperatures. |
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