FTIR analysis of cellulose treated with sodium hydroxide and carbon dioxide

Abstract

Cellulose samples treated with sodium hydroxide (NaOH) and carbon dioxide in dimethylacetamide (DMAc) were analyzed by FTIR spectroscopy. Absorbance of hydrogen-bonded OH stretching was considerably decreased by the treatment of NaOH and carbon dioxide. The relative absorbance ratio ( A 4000–2995/ A 993) represented the decrease of absorbance as a criterion of hydrogen-bond intensity (HBI). The absorbance of the band at 1430 cm −1 due to a crystalline absorption was also decreased by NaOH treatment. The absorbance ratio of the bands at 1430 and 987–893 cm −1 ( A 1430/ A 900), adopted as crystallinity index (CI), was closely related to the portion of cellulose I structure. With the help of FTIR equipped with an on-line evacuation apparatus, broad OH bending due to bound water could be eliminated. FTIR spectra of the carbon dioxide-treated cellulose samples at 1700–1525 cm −1 were divided into some bands including 1663, 1635, 1616, and 1593 cm −1. The broad OH bending due to bound water at 1641–1645 cm −1 was resolved to two bands at 1663 and 1635 cm −1. As a trace of DMAc, the band at 1616 cm −1 is disappeared by washing for the cellulose treated with carbon dioxide (Cell 1-C and Cell 2/60-C). The decrease of HBI, the easy removal of DMAc, and the band at 1593 cm −1 supported the introduction of new chemical structure in cellulose. The bands shown at 1593 and 1470 cm −1 was assigned as hydrogen-bonded carbonyl stretching and O–C–O stretching of the carbonate ion.