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Title: Thermoreversible Gels Composed of Colloidal Silica Rods with Short-Range Attractions

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
UNIVERSITYNIST
OSTI Identifier:
1330250
Resource Type:
Journal Article
Resource Relation:
Journal Name: Langmuir; Journal Volume: 32; Journal Issue: 33
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Murphy, Ryan P., Hong, Kunlun, and Wagner, Norman J. Thermoreversible Gels Composed of Colloidal Silica Rods with Short-Range Attractions. United States: N. p., 2016. Web. doi:10.1021/acs.langmuir.6b02107.
Murphy, Ryan P., Hong, Kunlun, & Wagner, Norman J. Thermoreversible Gels Composed of Colloidal Silica Rods with Short-Range Attractions. United States. doi:10.1021/acs.langmuir.6b02107.
Murphy, Ryan P., Hong, Kunlun, and Wagner, Norman J. 2016. "Thermoreversible Gels Composed of Colloidal Silica Rods with Short-Range Attractions". United States. doi:10.1021/acs.langmuir.6b02107.
@article{osti_1330250,
title = {Thermoreversible Gels Composed of Colloidal Silica Rods with Short-Range Attractions},
author = {Murphy, Ryan P. and Hong, Kunlun and Wagner, Norman J.},
abstractNote = {},
doi = {10.1021/acs.langmuir.6b02107},
journal = {Langmuir},
number = 33,
volume = 32,
place = {United States},
year = 2016,
month = 8
}
  • Dynamic arrest transitions of colloidal suspensions containing non-spherical particles are of interest for the design and processing of various particle technologies. To better understand the effects of particle shape anisotropy and attraction strength on gel and glass formation, we present a colloidal model system of octadecyl-coated silica rods, termed as adhesive hard rods (AHR), which enables control of rod aspect ratio and temperature-dependent interactions. The aspect ratios of silica rods were controlled by varying the initial TEOS concentration following the work of Kuijk et al. (J. Am. Chem. Soc., 2011, 133, 2346–2349) and temperature-dependent attractions were introduced by coating themore » calcined silica rods with an octadecyl-brush and suspending in tetradecane. The rod length and aspect ratio were found to increase with TEOS concentration as expected, while other properties such as the rod diameter, coating coverage, density, and surface roughness were nearly independent of the aspect ratio. Ultra-small angle X-ray scattering measurements revealed temperature-dependent attractions between octadecyl-coated silica rods in tetradecane, as characterized by a low-q upturn in the scattered intensity upon thermal quenching. Lastly, the rheology of a concentrated AHR suspension in tetradecane demonstrated thermoreversible gelation behavior, displaying a nearly 5 orders of magnitude change in the dynamic moduli as the temperature was cycled between 15 and 40 °C. We find the adhesive hard rod model system serves as a tunable platform to explore the combined influence of particle shape anisotropy and attraction strength on the dynamic arrest transitions in colloidal suspensions with thermoreversible, short-range attractions.« less
  • Charged colloids and proteins in aqueous solutions interact via short-range attractions and long-range repulsions (SALR) and exhibit complex structural phases. These include homogeneously dispersed monomers, percolated monomers, clusters, and percolated clusters. We report the structural architectures of simple charged systems in the form of spherical, Keggin-type heteropolyanions (HPAs) by small-angle X-ray scattering (SAXS) and molecular dynamics (MD) simulations. Structure factors obtained from the SAXS measurements show that the HPAs interact via SALR. Concentration and temperature dependences of the structure factors for HPAs with –3e (e is the charge of an electron) charge are consistent with a mixture of nonassociated monomersmore » and associated randomly percolated monomers, whereas those for HPAs with –4e and –5e charges exhibit only nonassociated monomers in aqueous solutions. Our experiments show that the increase in magnitude of the charge of the HPAs increases their repulsive interactions and inhibits their aggregation in aqueous solutions. MD simulations were done to reveal the atomistic scale origins of SALR between HPAs. As a result, the short-range attractions result from water or proton-mediated hydrogen bonds between neighboring HPAs, whereas the long-range repulsions are due to the distributions of ions surrounding the HPAs.« less
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