Néstor E. Valadez-Pérez

Metropolitan Autonomous University | UAM · Departamento de Física

The gravitational effects in gel-forming patchy colloidal systems are studied. We focus on how the gel structure is modified by gravity. Through Monte Carlo computer simulations of gel-like states recently identified by the rigidity percolation criterion, the influence of the gravitational field, characterized by the gravitational P\'eclet number,...

\textit{Hypothesis:} Particle aggregation is ubiquitous for many colloidal systems, and drives the phase separation or the formation of materials with a highly heterogeneous large-scale structure, such as gels, porous media and attractive glasses. While the macroscopic properties of such materials strongly depend on the shape and size of these part...

Competing interaction fluids have become ideal model systems to study a large number of phenomena, for example, the formation of intermediate range order structures, condensed phases not seen in fluids driven by purely attractive or repulsive forces, the onset of particle aggregation under in- and out-of-equilibrium conditions, which results in the...

During the last decade, there has been a hot debate about the physical mechanisms that determine when a colloidal dispersion approaches the gel transition. However, there is still no consensus on a possible unique route that leads to the conditions for the formation of a gel-like state. Based on gel states identified in experiments, Valadez-P\'erez...

We systematically investigated the structure and aggregate morphology of gel networks formed by colloid–polymer mixtures with a moderate colloid volume fraction and different values of the polymer–colloid size ratio, always in the limit of short-range attraction. Using the coordinates obtained from confocal microscopy experiments, we determined the...

Reversible aggregation of purely short-ranged attractive colloidal particles leads to the formation of clusters with a fractal dimension that only depends on the second virial coefficient. The addition of a long-ranged repulsion to the potential modifies the way in which the particles aggregate into clusters and form intermediate range order struct...

In this work, a new parametrization for the Statistical Association Fluid Theory for potentials of Variable Range (SAFT-VR) is coupled to the Discrete Potential Theory to represent the thermodynamic properties of several fluids, ranging from molecular liquids to colloidal-like dispersions. In this way, this version of the SAFT-VR approach can be st...

In this work we study the clustering of hard spheres (HS) with associating square-well (SW) sites of variable range as a model of polymerization process, like the ring-opening polymerization of the ϵ-caprolactone. We present a systematic Monte Carlo (MC) computer simulation study of the effects of the interaction parameters on the cluster morpholog...

We investigate the ability of a coarse-grained slip-link model and a simple double reptation model to describe the linear rheology of polydisperse linear polymer melts. Our slip-link model is a well-defined mathematical object that can describe the equilibrium dynamics and non-linear rheology of flexible polymer melts with arbitrary polydispersity...

Cluster morphology of spherical particles interacting with a short-range attraction has been extensively studied due to its relevance to many applications, such as the large-scale structure in amorphous materials, phase separation, protein aggregation and organelle formation in cells. Although it was widely accepted that the range of the attraction...

The so-called extended law of corresponding states, as proposed by Noro and Frenkel [J. Chem. Phys. 113, 2941 (2000)], involves a mapping of the phase behaviors of systems with short-range attractive interactions. While it has already extensively been applied to various model potentials, here we test its applicability to protein solutions with the...

The so-called extended law of corresponding states, as proposed by Noro and Frenkel [J. Chem. Phys. 113, 2941 (2000)], involves a mapping of the phase behaviors of systems with short-range attractive interactions. While it has already extensively been applied to various model potentials, here we test its applicability to protein solutions with thei...

Adding metallic nanoparticles into bulk-heterojunction, polymer-based solar cells has been proven an effective strategy to enhance light absorption of the active layer and device performance. However, the high-energy surfaces on the nanoparticles may also affect the morphology of the active layer by influencing phase-separation, which has not been...

Colloidal liquids interacting with short range attraction and long range repulsion, such as proposed for some protein solutions, have been found to exhibit novel states consisting of equilibrium particle clusters. Monte Carlo simulations are performed for two physically meaningful inter-particle potentials across a broad range of interaction parame...

Colloidal liquids interacting with short range attraction and long range repulsion, such as proposed for some protein solutions, have been found to exhibit novel states consisting of equilibrium particle clusters. Monte Carlo simulations are performed for two physically meaningful inter-particle potentials across a broad range of interaction parame...

One major goal in condensed matter physics is identifying the physical mechanisms that lead to arrested states of matter, especially gels and glasses. The complex nature and microscopic details of each particular system are relevant. However, from both scientific and technological viewpoints, a general, consistent and unified definition is of param...

Simple model systems with short-range attractive potentials have turned out to play a crucial role in determining theoretically the phase behavior of proteins or colloids. However, as pointed out by D. Gazzillo [J. Chem. Phys. 134, 124504 (2011)], one of these widely used model potentials, namely, the attractive hard-core Yukawa potential, shows an...

Percolation in suspensions driven only by short-ranged attractions has been studied for a long-time due to its imminent relation with equilibrium and non-equilibrium processes, such as gelation and glass transition. Recently, the effects of an additional long-range repulsion have received attention as the competition between both contributions of t...

One major goal in condensed matter physics is identifying the physical mechanisms that lead to arrested states of matter, especially gels and glasses. The complex nature and microscopic details of each particular system are relevant. However, from both scientific and technological viewpoints, a general, consistent and unified definition is of param...

The gelation is believed to result from the particle aggregation in a complex structure. The aggregate span in the entire volume gives it a capability for supporting stresses. Gelled systems possess a high degree of inhomogeneity, while locally the particles and their near neighbors present a defined array as can be seen in their coordination numbe...

The fluid phase behavior of colloidal suspensions with short-range attractive interactions is studied by means of Monte Carlo computer simulations and two theoretical approximations, namely, the discrete perturbation theory and the so-called self-consistent Ornstein-Zernike approximation. The suspensions are modeled as hard-core attractive Yukawa (...

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