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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Record number 539259
Title Compressive resistance of granular-scale microgels : From loose to dense packing
Author(s) Bouhid de Aguiar, Izabella; Schroën, Karin; Meireles, Martine; Bouchoux, Antoine
Source Colloids and Surfaces. A: Physicochemical and Engineering Aspects 553 (2018). - ISSN 0927-7757 - p. 406 - 416.
DOI https://doi.org/10.1016/j.colsurfa.2018.05.064
Department(s) Food Process Engineering
VLAG
Publication type Refereed Article in a scientific journal
Publication year 2018
Keyword(s) Compression resistance - Confocal microscopy - Dextran - Microgels - Osmotic pressure
Abstract Microgels are deformable and compressible particles that can be packed to concentrations that exceed the random close packing limit of hard spheres. For reaching high packing levels, one has to overcome the resistance to compression of the system. This resistance potentially originates from many different phenomena (thermal agitation effects, surface interactions, microgel deformation, interpenetration, water expulsion) that depend on the microgel properties (size, ionic charge, structure, softness). Here, we investigate granular-scale dextran-based microgels with different native water contents. The resistance to compression of the suspensions is measured through the variation of the osmotic pressure with packing concentration. In parallel, we characterize the structure of the packings in terms of polymer heterogeneity, microgel deformation, and average size using confocal microscopy. We find that all microgel suspensions resist compression in the same manner; however, the mechanisms involved clearly depend on the actual degree of compression. In the loose packing regime, the resistance originates mainly from the resistance of the microgels to their own deformation, with no or negligible deswelling; the osmotic pressure rises abruptly with concentration in analogy to compressed emulsion droplets. In the second and dense packing regime, the microgels necessarily have to expel water to withstand compression. The resistance of the packing is then similar to that of a continuous gel of the same polymer. Importantly, we find that structural macro-voids are still observable in these systems; the presence of which needs to be taken into account when modeling the osmotic resistance.
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