Moisture adsorption in TEMPO-oxidized cellulose nanocrystal film at the nanogram level based on micro-FTIR spectroscopy

The adsorbed water is known to have a significant influence on physical property of cellulose nanocrystal film. In order to characterize moisture adsorption of TEMPO oxidized cellulose nanocrystal film (TOCNF), a strategy for quantitative evaluation of moisture adsorption in TOCNF at the nanogram level is proposed here. In this approach, TOCNF spectra were in situ measured in a large range of relative humidity. Spectral analysis was applied to these measured spectra, and then moisture adsorption sites and spectrum ranges affected by moisture adsorption were identified. Based upon these confirmed spectrum ranges and moisture contents collected using dynamic vapor sorption apparatus, a micro-FTIR prediction model could be established using partial least squares regression. Afterwards, the established prediction model was used for acquiring moisture adsorption isotherm, and a good consistency between the forecasts and referential values was shown. It was confirmed this proposed strategy for quantitative evaluation of moisture adsorption in nanocellulose film at the nanogram level was effective.