Short and Soft: Multidomain Organization, Tunable Dynamics, and Jamming in Suspensions of Grafted Colloidal Cylinders with a Small Aspect Ratio

Journal Article · 02 December 2019 · Langmuir

DOI: https://doi.org/10.1021/acs.langmuir.9b03025 · OSTI ID:1804037

Parisi, Daniele ^[1]; Ruan, Yingbo ^[2]; Ochbaum, Guy ^[3]; Silmore, Kevin S.  ^[4]; Cullari, Lucas L. ^[3]; Liu, Chen-Yang  ^[2]; Bitton, Ronit ^[3]; Regev, Oren  ^[3]; Swan, James W. ^[4]; Loppinet, Benoit  ^[5]; Vlassopoulos, Dimitris  ^[6]

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1. Institute of Electronic Structure & Laser, FORTH, Heraklion 71110, Crete, Greece; Department of Materials Science & Technology, University of Crete, Heraklion 71003, Crete, Greece; OSTI
2. Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Engineering Plastics, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
3. Department of Chemical Engineering and the Ilze Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
4. Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge 02139, Massachusetts, United States
5. Institute of Electronic Structure & Laser, FORTH, Heraklion 71110, Crete, Greece
6. Institute of Electronic Structure & Laser, FORTH, Heraklion 71110, Crete, Greece; Department of Materials Science & Technology, University of Crete, Heraklion 71003, Crete, Greece

The yet virtually unexplored class of soft colloidal rods with a small aspect ratio is investigated and shown to exhibit a very rich phase and dynamic behavior, spanning from liquid to nearly melt state. Instead of the nematic order, these short and soft nanocylinders alter their organization with increasing concentration from isotropic liquid with random orientation to small domains with preferred local orientation and eventually a multidomain arrangement with a local orientational order. The latter gives rise to a kinetically suppressed state akin to structural glass with detectable terminal relaxation, which, on further increasing concentration, reveals features of hexagonally packed order as in ordered block copolymers. The respective dynamic response comprises four regimes, all above the overlapping concentration of 0.02 g/mL:(I) from 0.03 to 0.1 g/mol, the system undergoes a liquid-to-solidlike transition with a structural relaxation time that grows by 4 orders of magnitude. (II) From 0.1 to 0.2 g/mL, a dramatic slowing-down is observed and is accompanied by an evolution from isotropic to a multidomain structure. (III) Between 0.2 and 0.6 g/mol, the suspensions exhibit signatures of shell interpenetration and jamming, with the colloidal plateau modulus depending linearly on concentration. (IV) At 0.74 g/mL, in the densely jammed state, the viscoelastic signature of hexagonally packed cylinders from microphase-separated block copolymers is detected. These properties set short and soft nanocylinders apart from long colloidal rods (with a large aspect ratio) and provide insights for fundamentally understanding the physics in this intermediate soft colloidal regime and for tailoring the flow properties of nonspherical soft colloids.

• Research Organization: Krell Institute, Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: FG02-97ER25308
• OSTI ID: 1804037
• Journal Information: Langmuir, Journal Name: Langmuir Journal Issue: 52 Vol. 35; ISSN 0743-7463
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English

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