The liquid-glass-jamming transition in disordered ionic nanoemulsions

In quenched disordered out-of-equilibrium many-body colloidal systems, there are important distinctions between the glass transition, which is related to the onset of nonergodicity and loss of low-frequency relaxations caused by crowding, and the jamming transition, which is related to the dramatic increase in elasticity of the system caused by the deformation of constituent objects. For softer repulsive interaction potentials, these two transitions become increasingly smeared together, so measuring a clear distinction between where the glass ends and where jamming begins becomes very difficult or even impossible. Here, we investigate droplet dynamics in concentrated silicone oil-in-water nanoemulsions using light scattering. For zero or low NaCl electrolyte concentrations, interfacial repulsions are soft and longer in range, this transition sets in at lower concentrations, and the glass and the jamming regimes are smeared. However, at higher electrolyte concentrations the interactions are stiffer, and the characteristics of the glass-jamming transition resemble more closely the situation of disordered elastic spheres having sharp interfaces, so the glass and jamming regimes can be distinguished more clearly

A new class of copolymer colloids with tunable, low refractive index for investigations of structure and dynamics in concentrated suspensions

Highly charged polymer colloids may serve as model systems for the investigation of condensed matter, if they self-organize to liquid-like, glassy or crystalline phases. Multiple scattering due to refractive index differences of colloidal particles and suspending medium is a serious problem when utilizing light scattering experiments for these investigations. In this work, a new class of monodisperse colloidal dispersions is prepared by means of emulsion copolymerization of the monomers n-butyl acrylate and 2,2,2-trifluoroethyl acrylate. By systematic variation of the molar ratio of fluorinated and non-fluorinated monomers, the refractive index n p of the colloidal copolymer particles is tuned in the range 1.38 < n p < 1.45. Thus, particles with any composition of both monomers can be index-matched by protic water/glycerol mixtures as demonstrated by minima of the relative transmission of suspensions in dependence on the refractive index of the suspending medium. Static and dynamic light scattering experiments as well as analysis of the static structure factors S(Q) by means of integral equations are employed to investigate the self-organization of the resulting colloidal copolymer particles. Hereby, the potential application of these new model systems to investigate dynamics in concentrated binary mixtures is demonstrated