Specific interactions in model charged polysaccharide systems

Temporary networks were obtained from mixtures of two derivatized chitosans, one with P-cyclodextrin (CD) cavities and the other with adamantyl (AD) moieties, randomly distributed along the chains. The viscoelastic response of these original systems in which cyclodextrin-adamantane complexes play a role of interchain junctions (sticky points) was investigated as a function of polymer concentration, degree of modification, ionic strength, temperature, and addition of competitive molecules. In the semidilute regime, an increase of the long relaxation times with the density of CD-AD complexes is observed, reflecting the hindrance of local flow processes due to reversible interchain bonds. The strong dependence of the apparent relaxation energy appears as a consequence of the temperature dependence of CD-AD interaction. However, contrary to the long time dynamics, the elastic plateau modulus of the transient network at short times does not seem to be much influenced by the density of stickers. The value of the plateau modulus is mainly dependent on polymer concentration.