Hierarchical cross-linking in physical alginate gels: a rheological and dynamic light scattering investigation

摘要

We investigate the dynamics of alginate gels, an important class ofbiopolymer-based viscoelastic materials, by combining mechanical tests andnon-conventional, time-resolved light scattering methods. Two relaxation modesare observed upon applying a compressive or shear stress. Dynamic lightscattering and diffusive wave spectroscopy measurements reveal that these modesare associated with discontinuous rearrangement events that restructure the gelnetwork via anomalous, non-diffusive microscopic dynamics. We show that thesedynamics are due to both thermal activation and internal stress stored duringgelation and propose a scenario where a hierarchy of cross-links with differentlife times is responsible for the observed complex behavior. Measurements atvarious temperatures and sample ages are presented to support this scenario.