Microstructure evolution of multivalent ion-complexed polyelectrolyte gels

Ions perform crucial functions in biological systems. However, the understanding of the relation between polyelectrolyte gel and ion is confined to the effects of swelling by salt solutions on macro- and micro-properties of gel. Here we explore the microstructure evolution of gel with changing crosslinking density and concentration of types of salts measured by dynamic light scattering (DLS). The dissociation-association of the ion bonds will induce a stretched exponential mode in the correlation function. The stretched exponent β reflects the subchain dynamics of gel strands and undergoes a transition from 0.33 to 0.5 when the multivalent salt concentration increases to the vicinity of phase separation boundary. It demonstrates that the Gaussian chain-like gel strands with Rouse dynamics transform into molten-globule-like strands with Zimm dynamics at high multivalent salt concentration.