Contribution of different state of adsorbed water to the sub-Tg dynamics of cellulose.

The contribution of different states of adsorbed water to the sub-Tg dynamics of cellulose was investigated by means of dielectric spectroscopy in couple with LF-NMR. The distribution and hydration state of adsorbed water in cellulose were determined by LF-NMR, based on which the role that different state of adsorbed water plays in typical secondary dielectric relaxations is discussed in detail. The variation of the dynamic characteristics of these relaxations suggested that three states of bound water present in moist cellulose, including tightly bound, non-freezable loosely bound, and freezable loosely bound water. It was discovered that different state of adsorbed water has obviously different contribution to these relaxations and the role that a certain state of bound water plays in different relaxations also varies. For cellulose with very high moisture content, an additional relaxation due to the dynamics of interfacial ice-like water was also observed.