1,721,053 research outputs found
Models of gel-forming colloids
No full textWe study the phenomenon of structral arrest in colloidal suspensions, with emphasis on the equilibrium and non-equilibrium routes to gel formation. We describe a number of model systems, treated with molecular dynamics simulations, which give rise to equilibrium gels in a wide region of volume fractions of the dispersed phase. These models have in common the anisotropy of the mutual interactions and show a set of characteristic features, i.e. the drastic reduction of the unstable two-phase region ('empty liquids'), the Arrhenius form decay for the diffusivity, the typical behavior of strong glasses, and the approach to an ideal gel state due to bonding among the particles. We also show that anisotropic interactions allow self-assembly in colloids to be treated using an equilibrium liquid-state approach. © 2008 American Institute of Physics
Glassy colloidal systems
No full textThis review focuses on recent developments in the theoretical, numerical and experimental study of slow dynamics in colloidal systems, with a particular emphasis on the glass transition phenomenon. Colloidal systems appear to be particularly suited for tackling the general problem of dynamic arrest, since they show a larger flexibility compared to atomic and molecular glasses because of their size and the possibility of manipulating the physical and chemical properties of the samples. Indeed, a wealth of new effects, not easily observable in molecular liquids, have been predicted and measured in colloidal systems. The slow dynamic behavior of three classes of colloidal suspension is reviewed - hard colloids, short-range attractive colloids and soft colloidal systems - selecting the model systems among the most prominent candidates for grasping the essential features of dynamic arrest. Emphasis is on the possibility of performing a detailed comparison between experimental data and theoretical predictions based on the mode coupling theory of the glass transition. Finally, the importance of understanding the system's kinetic arrest phase diagram, i.e. the regions in phase space where disordered arrested states can be expected, is stressed. When and how these states are kinetically stabilized with respect to the ordered lowest free energy phases is then examined in order to provide a framework for interpreting and developing new ideas in the study of new materials
Association of limited valence patchy particles in two dimensions
No full textWe investigate theoretically the phase behavior of particles with limited valence in two dimensions, by solving the first-order Wertheim theory form. As previously found for three dimensions, in two dimensions also the valence has a strong impact on the phase diagram, controlling the location of the gas-liquid coexistence. On decreasing the valence, the critical density and temperature decrease while the region of gas-liquid instability shrinks and vanishes. At low temperatures, the system reaches its ground state with particles forming a fully bonded network which spans the system
Viscoelastic processes in non ergodic states (percolation and glass transitions) of attractive micellar systems
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