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Microstructure-driven self-assembly and rheological properties of multi-responsive soft microgel suspensions

Abstract : Hypotheses The deformation and swelling ability of microgels is influenced by the crosslinking distribution. Varying microgels microstructure is expected to obtain suspensions with different flow behavior and thereby, different rheological properties. Experiments Different multi-responsive microgels were synthesized using two different crosslinkers and varying their amounts: N,N-methylene bis-acrylamide (MBA) and oligo(ethylene glycol) diacrylate (OEGDA). The rheological results were obtained by zero-shear viscosity and long-time creep measurements on concentrated microgel suspensions Microgel microstructure was analyzed by 1H nuclear magnetic resonance transverse relaxation measurements. Findings At a constant crosslinking rate, we show that the viscosity of OEGDA-crosslinked microgels diverges at a higher concentration than MBA ones, suggesting a looser shell and less restricted dangling chains at the periphery for the later. By scaling with the effective volume fraction, the viscosity curves of the different microgel suspensions reduce into a single curve and closely follow hard sphere models up to ϕeff < 0.45. The results from creep tests revealed a much higher yield stress for MBA-crosslinked microgels, strengthening the hypothesis of a looser shell for the later. Finally, transverse relaxation (T2) NMR measurements demonstrated that, although all microgels exhibit a core–shell microstructure, MBA samples present a less crosslinked shell corroborating with the rheological results.
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https://hal-univ-pau.archives-ouvertes.fr/hal-02911025
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Submitted on : Tuesday, January 18, 2022 - 9:59:28 AM
Last modification on : Sunday, June 26, 2022 - 3:31:36 AM

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Éva Dieuzy, Garbine Aguirre, Stéphane Auguste, Kamel Chougrani, Valérie Alard, et al.. Microstructure-driven self-assembly and rheological properties of multi-responsive soft microgel suspensions. Journal of Colloid and Interface Science, Elsevier, 2021, 581 (Part B), pp.806-815. ⟨10.1016/j.jcis.2020.07.137⟩. ⟨hal-02911025⟩

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