Heterogeneity in nanocomposite hydrogels from poly(ethylene oxide) cross-linked with silicate nanoparticles

We investigate the influence of ionic strength on the structural heterogeneity and viscoelastic properties of nanocomposite hydrogels. We use small-angle scattering and rheology to monitor structural changes as a function of ionic strength. Increasing ionic strength makes the nanocomposite gels macroscopically heterogeneous, stiffer and more turbid. At high shear rates, nanometre structures rearrange within aggregates and orient in the flow direction. The changing structural properties that develop with ionic strength are due to increased heterogeneity of nanoparticle distribution and polymer-nanoparticle interactions as well as to the formation of PEO [poly(ethylene oxide)] aggregates interacting with sodium cations, which reinforce the overall hydrogel network.