Determination of sulfate esterification levels in cellulose nanocrystals by attenuated total reflectance - Fourier transform infrared spectroscopy

Cellulose nanocrystals were produced by hydrolyzing cotton cellulose with high concentration sulfuric acid. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used as a simple method to quantify the sulfate esterification levels of cellulose nanocrystals(CNCs) with different post treatments. Understanding the surface chemistry of cellulose is critical for creating realistic model systems for studying lignocellulose assembly. Cellulose nanocrystals prepared by a less efficient hydrochloric acid treatment, which do not have the sulfate content, were used as the zero sulfate standards. Dextran sulfate was added to the zero standards in order to create calibration curves. Our results indicate that both post hydrochloric acid and pyridine treatment after the sulfuric acid hydrolysis process did not remove the sulfate groups on the cellulose nanocrystals effectively, in contract to previously published data. Our data suggests that this method did not work well on cellulose and only cellulose pyridinium salts were obtained. This is under further study.