Dynamic vapor sorption and thermoporometry to probe water in celluloses
2012
Driemeier, Carlos | Mendes, Fernanda M. | Oliveira, Marcelo M.
Dynamic vapor sorption and thermoporometry probe complementary dimensions of water interaction with cellulose. While sorption is primarily sensitive to the first hydration layers, thermoporometry is primarily sensitive to the nanometric water-filled pores. In this article, these analytical techniques are detailed and applied to model mesoporous materials and to a wide spectrum of celluloses. Correlations between techniques are explored. In dynamic vapor sorption, celluloses present a general characteristic time of desorption. On the other hand, they present highly variable characteristic times of sorption, indicating that material-specific properties may be inferred from sorption kinetics. Regarding thermoporometry, the thermodynamics of ice melting in irregular pore shapes is introduced. Moreover, in our thermoporometry analysis with differential scanning calorimeter, freezing temperature is extended to −70 °C, allowing pores smaller than a few nanometers to be measured. Nevertheless, several data corrections are required for accurate thermoporometry at this condition. Comparisons between techniques show that sorption hysteresis is positively correlated with wet porosity. The presented developments and results will guide future application of these techniques to probe water in celluloses.
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