Probing molecular interactions of polysaccharides in the presence of water

Herein we report new dielectric relaxation processes at high frequency (ca. 1.2•108 Hz) in polysaccharides pellets (cellulose, chitin, chitosan, starch and amylopectin) that are traceable to strong OH–H2O interactions. Temperature dependence of high frequency dielectric relaxation behavior is investigated using dielectric spectroscopy. In situ temperature FTIR, XRD and TGA measurements are studied to assess relaxation processes related to vibration of OH groups. Upon heating below the glass transition there appears an Arrhenius-type dependence with negative activation energy; this is due to re-orientation of dipoles to lower energy. Upon further heating a glass transition is observed and then there appears another Arrhenius-type process with positive activation energy due to the increasing of random thermal motions of chains, water molecule evaporation and hydrogen bonding destruction. In dry samples the activation energies of this relaxation are practically zero because no exist water molecules and OH groups of polysaccharides are trapped in a potential well.