Observation of empty liquids and equilibrium gels in a colloidal clay

Abstract

The relevance of anisotropic interactions in colloidal systems has recently emerged in the context of the rational design of new soft materials. Patchy colloids of different shapes, patterns and functionalities are considered the new building blocks of a bottom-up approach toward the realization of self-assembled bulk materials with predefined properties. The ability to tune the interaction anisotropy will make it possible to recreate molecular structures at the nano- and micro-scales (a case with tremendous technological applications), as well as to generate new unconventional phases, both ordered and disordered. Recent theoretical studies suggest that the phase diagram of patchy colloids can be significantly altered by limiting the particle coordination number (that is, valence). New concepts such as empty liquids—liquid states with vanishing density—and equilibrium gels—arrested networks of bonded particles, which do not require an underlying phase separation to form—have been formulated. Yet no experimental evidence of these predictions has been provided. Here we report the first observation of empty liquids and equilibrium gels in a complex colloidal clay, and support the experimental findings with numerical simulations.

In-Depth Insights into the Key Steps of Delamination of Charged 2D Nanomaterials

“…Experimentally, we observed no visible phase separation even over periods of several months. It may nevertheless be that at much longer periods (> 1 year) and despite very slow kinetics segregation might occur (37). Below this volume fraction the two microphases start to macroscopically phase separate by gravitation as shown in Fig.…”

Glass–glass transition during aging of a colloidal clay

“…The tunability of colloidal effective interactions 1 offers the possibility to observe unusual phase diagrams 2 including reentrant 3,4 or empty liquid 5,6 regimes, and multiple arrested states, such as gels 7,8 and glassy states 9,10 . Of particular interest are glass-glass transitions 3,4,11,12 , which are quite rare to be found, especially at ambient conditions.…”

“…In addition to their vast potential applications, their anisotropic shape and complex interactions considerably enrich their phase diagram 6,[15][16][17] and make them suitable candidates for self-assembly 18 . Among these, Laponite suspensions, widely used in cosmetics, oil industry, paints, have emerged as intriguing systems with peculiar aging dynamics and unexpected phase behaviour [19][20][21][22][23] .…”

Self-assembling knots of controlled topology by designing the geometry of patchy templates

“…For instance, colloidal scientists and soft matter physicists have explored the feasibility of self-assemblying extended photonic crystals and other metamaterials by designing patchy particles of increasingly complex surface activity [1][2][3][4] , by exploiting the shape anisotropy of convex polyhedrical colloids 5,6 or by choosing to disperse particles into complex fluids such as binary fluids or liquid crystals [7][8][9][10] . The resulting interparticle interactions are in general highly non-trivial and can promote the formation of crystals, glasses, gels and so on, often with tunable physical properties 11 .…”