Rheology of nanoemulsions in glass and compressed-droplet states

The soft matter of interest in this study is concentrated oil-in-water nanoemulsions, in which the content of a polymer depletant is varied. First, dilute nanoemulsions with 25% volume fraction are prepared, containing poly(ethylene glycol)-diacrylate (PEGDA) and sodium dodecyl sulfate (SDS) as depletant and ionic surfactant, respectively. Then, they are concentrated to higher volume fractions through evaporation of continuous phase under controlled conditions. Estimation of the interdroplet interactions and effective volume fractions indicates that nanoemulsions in repulsive glass, attractive glass, and compressed-droplet states can be produced. We evaluate the interfacial tension of water-oil phase and rheological properties of concentrated nanoemulsions. The results show that the equilibrium interfacial tension is independent of PEGDA content. The scaled rheological properties of concentrated nanoemulsions at glass and compressed-droplet states do not superimpose for different contents of PEGDA, which can be attributed to the PEGDA-SDS complexation.