Thermodynamics of the swelling work of wood and non-ionic polysaccharides: A revisit

Polysaccharides, even non-ionic ones, swell in water with potentially huge pressure, which can be sources of intended actuation or a cause of structural damage. The swelling pressure has been investigated since the 19th century, and thermodynamic considerations developed at the beginning of the 20th century. Such treatment is revisited with currently available data showing the swelling to be mostly enthalpy driven. The molecular origin of the heat of swelling is discussed, considering the specificity of polysaccharides or biopolymers with relatively stiff chain conformation that contradicts the compact packing of enthalpy stabilization. Part of the heat of swelling, and thus the potential work of swelling, would originate from the elastic energy stored in the rigid structure. This vision can be tested in the conception of actuation or control of swelling.