Droplet Dispersion States of Cyclodextrin-Based Emulsions fromNonlinear Rheological Properties

Polymers are desirable to improve emulsion stabilityby stuffing them into the continuous phase. How to getinformation on the droplet dispersion states of the emulsionsremains a challenge, as the emulsion characteristics are dictated bytwo intertwining components, the polymer matrix and the droplets.Herein, we use an amphiphilic polymer, gum arabic (GA), tomediate the dropletflocculation of cyclodextrin (CD)-basedemulsions and compare them with our previous studies on thestabilization of CD-based emulsions by a nonamphiphilic polymer,methylcellulose (MC). We characterize the emulsions by usingoptical microscopy, confocal laser scanning microscopy, and laserparticle analysis, explore their rheological behavior through large-amplitude oscillatory shear experiments, and analyze the nonlinear viscoelasticities through Fourier transform (FT)-rheology andLissajous-Bowditch plots. There is a great difference between GA and MC in the viscosity effect and the arrangement aroundemulsion droplets. GA is not an effectiveflocculation inhibitor due to a bridgingflocculation mechanism rather than a directviscosity effect. Our analysis highlights the role of the intrinsic nonlinearity parameter (Q0) extracted by FT analysis in reflecting thedroplet dispersion states of the emulsions by decoupling structural contributions from the polymers and the emulsion droplets.