Qualitatively and quantitatively characterizing water adsorption of a cellulose nanofiber film using micro-FTIR spectroscopy

The efficient utilization of cellulose is very important for environmental protection and sustainability of resources. A cellulose derivative, cellulose nanofiber film, is a highly promising candidate for use in tissue engineering, electronics, and green packaging materials; however, water adsorption seriously impairs the properties of cellulose nanofiber film. In order to efficiently utilize this cellulose derivative, we need to qualitatively and quantitatively characterize its water adsorption. In situ micro-FTIR spectra of the cellulose nanofiber film were collected within a relative humidity (RH) range of 0–94%. The spectral information indicated effective adsorption sites for adsorbed water and identified three spectral regions closely associated with water absorption. Meanwhile, moisture contents of the cellulose nanofiber film were measured by dynamic vapor sorption as reference values. Using a partial least squares regression (PLS-R) method, the identified spectral regions closely associated with water absorption were used to construct a multivariate quantitative model to predict moisture contents of cellulose nanofiber film over the entire RH range. The predicted sorption isotherm confirmed the effectiveness of the micro-FTIR spectroscopy in quantitatively characterizing water adsorption of the cellulose nanofiber film at room temperature of 25 °C.