Departamento de Física
URI permanente para esta comunidadhttps://hdl.handle.net/10953/33
En esta Comunidad se recogen los documentos generados por el Departamento de Física y que cumplen los requisitos de Copyright para su difusión en acceso abierto.
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Examinando Departamento de Física por Materia "2 Chemistry"
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Ítem Coarse-grained Monte Carlo simulations of nanogel-polyelectrolyte complexes: electrostatic effects(Royal Society of Chemistry, 2020-02-14) Pérez-Mas, Luis; Martín-Molina, Alberto; Quesada-Pérez, ManuelCoarse-grained Monte-Carlo simulations of nanogel-polyelectrolyte complexes have been carried out. The results presented here capture two phenomena reported in experiments with real complexes: (i) the reduction in size after absorbing just a few chains and (ii) the charge inversion detected through electrophoretic mobility data. Our simulations reveal that charge inversion occurs if the polyelectrolyte charge is large enough. In addition, the distribution of chains inside the nanogel strongly depends on whether charge inversion takes place. It should also be stressed that the chain topology has little influence on most of the properties studied here.Ítem Coarse-grained simulations of diffusion controlled release of drugs from neutral nanogels: Effect of excluded volume interactions(AIP Publishing, 2020-01-08) Maroto-Centeno, José-Alberto; Quesada-Pérez, ManuelThe primary goal of this work is to assess the effect of excluded volume interactions on the diffusion controlled release of drug molecules from a spherical, neutral, inert, and cross-linked device of nanometric size. To this end, coarse-grained simulations of the release process were performed. In this way, the inner structure and topology of the polymer network can be explicitly taken into account as well. Our in silico experiments reveal that the boundary condition of constant surface concentration is not appropriate for nanogels. In particular, the predictions based on the perfect sink condition clearly overestimate the fraction of drug released. In addition, these simulations provide values for the release exponent that depends on both the diameter of drug molecules and the number of drug molecules loaded in the matrix, which clearly contrasts with the classical prediction of a constant release exponent. Consequently, the widely used classification of drug release mechanisms based on this kinetic exponent must be extended to include new situations.Ítem Coarse-Grained Simulations of Solute Diffusion in Crosslinked Flexible Hydrogels(ACS Publications, 2022-02-22) Quesada-Pérez, Manuel; Maroto-Centeno, José-Alberto; Ramos-Tejada, María del Mar; Martín-Molina, AlbertoIn this work, the longtime diffusion of a solute in a chemically crosslinked and flexible hydrogel is computed from a coarse-grained model of a polymeric network. The effects of different key parameters of this model on diffusion are assessed. The relevance of chain flexibility becomes important by increasing the polymer volume fraction and the solute size. In fact, the solute particle can moderately diffuse in flexible hydrogels even when its diameter is comparable to the mesh size. The diffusion coefficients obtained here are tested by comparing with the previously reported experimental data. A reasonably good agreement between the experiment and simulation is found without requiring any adjustable parameter.Ítem Electrostatic hindrance to diffusion in flexible crosslinked gels: A coarse-grained simulation study(AIP Publishing, 2023-07-05) Pérez-Mas, Luis; Ramos-Tejada, María del Mar; Martín-Molina, Alberto; Maroto-Centeno, José ALberto; Quesada-Pérez, ManuelIn this work, we study how electrostatic forces slow down the diffusion of solute in flexible gels through coarse-grained simulations. The model used explicitly considers the movement of solute particles and polyelectrolyte chains. These movements are performed by following a Brownian dynamics algorithm. The effect of three electrostatic parameters characterizing the system (solute charge, polyelectrolyte chain charge, and ionic strength) is analyzed. Our results show that the behavior of both the diffusion coefficient and the anomalous diffusion exponent changes upon the reversal of the electric charge of one of the species. In addition, the diffusion coefficient in flexible gels differs significantly from that in rigid gels if the ionic strength is low enough. However, the effect of chain flexibility on the exponent of anomalous diffusion is significant even at high ionic strength (100 mM). Our simulations also prove that varying the polyelectrolyte chain charge does not have exactly the same effect as varying the solute particle charge.Ítem Solute diffusion in gels: Thirty years of simulations(Elsevier, 2021-01) Quesada-Pérez, Manuel; Martín-Molina, AlbertoIn this review, we present a summary of computer simulation studies on solute diffusion in gels carried out in the last three decades. Special attention is paid to coarse-grained simulations in which the role of steric and electrostatic interactions on the particle diffusion can be evaluated In addition, other important characteristics of particle diffusion in gels, such as the stiffness of the gel structure and hydrodynamic interactions, can be taken into account through coarse-grained simulations. Emphasis is placed on how simulation results help to test phenomenological models and to improve the interpretation interof experimental results. Finally, coarse-gained simulations have also been employed to study the diffusion controlled release of drugs from gels. We believe that scientific advances in this line will be useful to better understand the mechanisms that control the diffusive transport of molecules in a wide variety of biological systems.