Peculiar behavior of polysaccharide/borax hydrogel tablets: a dynamomechanical characterization

The peculiar unidirectional elongation observed during swelling of tablets prepared with scleroglucan (Sclg) and borax was compared with that of other synthetic and natural polymers capable of physical/chemical interactions with borate ions. A dynamomechanical characterization of “squared” Sclg/borax tablets was carried out to study the differences detectable on the two sides of the matrix corresponding to the two directions, respectively, the parallel and perpendicular one with respect to the applied compression force. Different compression forces were used and, in some cases, a second compression was applied on the tablets along a direction perpendicular to the first one. Birefringence experiments were carried out on the swelled tablets along the two directions. Obtained results allow correlating the anisotropic swelling behavior with the detected dynamomechanical and optical properties of the Sclg/borax system. Among the various tested polymers, only guar gum and, to a lesser extent, locust bean gum, showed an anisotropic elongation during swelling.