Interaction between sorbed water and Xylan studied by IR spectroscopy

Using the differential registration of spectra of water-swollen relative to the corresponding dry samples, IR spectra of water sorbed by xylan at relative different humidities were measured and interpreted. The specific intermolecular interactions operative in the polymer at different degrees of hydration were studied. Hydrogen bonds between water molecules and OH-groups on the C2 and C3 carbon atoms in the repeating unit are not equivalent energetically. It has been shown that sorption of water facilitates the formation of a more homogeneous system of OH-group rotamers. The effect of sorbed water on molecular orientation at various degrees of hydration is discussed on the basis of the measured IR dichroism.