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Viscoelastic necking dynamics between attractive microgels

Chen, Shensheng and Pirhadi, Emad and Yong, Xin (2022) Viscoelastic necking dynamics between attractive microgels. Journal of Colloid and Interface Science, 618 . pp. 283-289. ISSN 0021-9797. doi:10.1016/j.jcis.2022.03.048.

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Hypothesis. Microgels can deform and interpenetrate and display colloid/polymer duality. The effective interaction of microgels in the collapsed state is governed by the interplay of polymer–solvent interfacial tension and bulk elasticity. A connecting neck is shown to mediate microgel interaction, but its temporal evolution has not been addressed. We hypothesize that the necking dynamics of attractive microgels exhibits liquid-like or solid-like behavior over different time and length scales. Experiments. We simulate the merging and pinching of attractive microgels with different crosslinking densities in explicit solvent using dissipative particle dynamics. The temporal coalescence dynamics of microgels is investigated and compared with simple liquid and polymeric droplets. We model the neck growth on long time scales using Maxwell model of polymer relaxation and compare the theoretical prediction with simulation data. The mechanical strength of the neck is characterized systematically via simulated pinch-off of microgels by steered molecular dynamics. Findings. We evidence a crossover in the coalescence dynamics reflecting the viscoelastic signature of microgels. In contrast to the common knowledge that viscoelastic materials respond elastically on short time scales, the early expansion of the microgel neck exhibits a linear behavior, similar to the viscous coalescence of liquid droplets. However, the late regime with arrested dynamics resembles sintering of solid particles. Through an analytical model relating microgel dynamics to neck growth, we show that the long-term behavior is governed by stress relaxation of the polymers in the neck region and predict an exponential decay in the rate of growth, which agrees favorably with the simulation. Different from coalescence, the thread thinning in microgel breakup primarily highlights its polymeric characteristics.

Item Type:Article
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Chen, Shensheng0000-0002-6427-935X
Additional Information:© 2022 Elsevier. Received 7 December 2021, Revised 10 March 2022, Accepted 11 March 2022, Available online 15 March 2022, Version of Record 25 March 2022. We gratefully acknowledge funding from the National Science Foundation under Grant No. CMMI-1939362 for partial support of this research. Generous allocation of computing time was provided by the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. CRediT authorship contribution statement: Shensheng Chen: Conceptualization, Methodology, Software, Investigation, Formal analysis, Visualization, Writing – original draft. Emad Pirhadi: Investigation, Formal analysis, Writing – review & editing. Xin Yong: Conceptualization, Visualization, Supervision, Writing – review & editing, Funding acquisition. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0012704
Subject Keywords:Attractive microgels; Viscoelasticity; Droplet coalescence; Dissipative particle dynamics; Maxwell model
Record Number:CaltechAUTHORS:20220721-7978000
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Official Citation:Shensheng Chen, Emad Pirhadi, Xin Yong, Viscoelastic necking dynamics between attractive microgels, Journal of Colloid and Interface Science, Volume 618, 2022, Pages 283-289, ISSN 0021-9797,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115718
Deposited By: George Porter
Deposited On:22 Jul 2022 19:57
Last Modified:22 Jul 2022 19:57

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