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Descripción
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| Stable, unstable and metastable structuring of confined polymer blends at off-critical concentrations deposited on a solid substrate and with a free evolving surface is presented. The non-linear solutions are obtained numerically using a variational form of the Cahn-Hilliard equation in the static limit, which allows for internal diffuse interfaces between the two components of the mixture. The upper free surface is sharp and free to move, allowing strong deformations. Varying the average composition, the size of the films and the surface energy we find a rich morphology of static films in the form of laterally structure films, layered films, droplets on the substrate, droplets on the free surface, and checkerboard structures. We show that structured solutions are energetically favorable over homogeneous states within the whole spinodal region and find the states of absolute stability. Existence of most of the branches of non-linear solutions at off-critical mixture concentrations can be predicted from the knowledge of the non-linear solutions at critical compositions plus the branching points at off-critical compositions derived from a simple linear stability analysis. However, some families of solutions have no correspondence at critical compositions [1]. We study as well the transport by convection through the named model-H, which generalizes the Cahn-Hilliard model by coupling the momentum transport to diffusion of the components. Model-H is extended to account for free surface boundary conditions allowing us to study the combined effect of phase separation within a film of polymer blend and structuring of the surface of the film itself [2]. We apply it to analyze the stability of vertically stratified steady extended films and show that convective transport leads to new mechanisms of instability as compared to the simpler purely diffusive case described by the Cahn-Hilliard model [3]. Santiago Madruga acknowledges support by the Spanish Ministerio de Economa y Competitividad via the projects TRA2013-45808-R and ESP2013-45432-P. [1] F. Bribesh, S. Madruga and U. Thiele. Two-dimensional steady states in off-critical mixtures with high interface tension. Eur. Phys. J. Spec. Top. 219:3-12, 2013. [2] U. Thiele, S. Madruga, and L. Frastia. Decomposition driven interface evolution for layers of binary mixtures: I. model derivation and base states. Phys. Fluids, 19:122106, 2007. [3] S. Madruga and U. Thiele. Decomposition driven interface evolution for layers of binary mixtures: II. influence of convective transport on linear stability. Phys. Fluids, 21:062104, 2009. | |
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Internacional
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Si |
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Nombre congreso
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13th U.S. National Congress on Computational Mechanics |
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Tipo de participación
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960 |
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Lugar del congreso
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San Diego, EEUU |
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Revisores
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Si |
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ISBN o ISSN
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00-0000-000-0 |
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DOI
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Fecha inicio congreso
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26/07/2016 |
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Fecha fin congreso
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30/07/2016 |
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Desde la página
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657 |
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Hasta la página
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657 |
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Título de las actas
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Abstract Book |