Dynamic behavior of tough polyelectrolyte complex hydrogels from chitosan and sodium hyaluronate

In this work, we investigated the dynamics of hydrogels from the polyelectrolyte complexation of sodium hya-luronate (HA) and chitosan under various temperature and salt concentration. Raising temperature and adding salt remarkably reduce the mechanical behavior of hydrogels. The stress relaxation of semi-flexible chain seg-ments is accelerated at high temperature and salt concentration, which is controlled by thermally activated bond disassociation process. The flow activation energy determined from temperature-dependent dynamic light scattering decorrelation and rheological relaxation are in very good agreement. Our results suggest that the chain aggregations are physical crosslinked by surrounded semi-flexible chains, and their diffusion is highly hindered by the topological entanglements and ionic associations. The synergistic effect of aggregations diffusion and chain dynamics causes the slow macroscopic stress relaxation behavior of hydrogels before yield, independent of applied strain. Above yield, the amplitude of strain accelerates the stress relaxation, resulting in chain disen-tanglements and slipping.

Automated summary

In this work, the dynamics of hydrogels from the polyelectrolyte complexation of sodium hyaluronate and chitosan under different temperature and salt concentration were investigated. The study found that increasing temperature and adding salt significantly reduce the mechanical behavior of hydrogels. The stress relaxation of semi-flexible chain segments is accelerated at high temperature and salt concentration, which is controlled by a thermally activated bond dissociation process. The study also revealed that the chain aggregations in hydrogels are physically crosslinked by surrounded semi-flexible chains, and their diffusion is hindered by topological entanglements and ionic associations.