Micellar Mimicry of Intermetallic C14 and C15 Laves Phases by Aqueous Lyotropic Self-Assembly

Carlos M. Baez-Cotto; Mahesh K. Mahanthappa

doi:10.1021/acsnano.7b07475

Micellar Mimicry of Intermetallic C14 and C15 Laves Phases by Aqueous Lyotropic Self-Assembly

Carlos M. Baez-Cotto, Mahesh K. Mahanthappa

Research output: Contribution to journal › Article › peer-review

67 Scopus citations

Abstract

Concentration-dependent supramolecular self-assembly of amphiphilic molecules in water furnishes a variety of nanostructured lyotropic liquid crystals (LLCs), which typically display high symmetry bicontinuous network and discontinuous micellar morphologies. Aqueous dispersions of soft spherical micelles derived from small molecule amphiphile hydration typically pack into exemplary body-centered cubic and closest-packed LLCs. However, investigations of hydrated mixtures of the ionic surfactant tetramethylammonium decanoate loaded with 40 wt % n-decane (TMADec-40) revealed the formation of a high symmetry bicontinuous double diamond LLC, as well as cubic C15 and hexagonal C14 Laves LLC phases that mirror the MgCu₂ and MgZn₂ intermetallic structure types, respectively. Detailed small-angle X-ray scattering analyses demonstrate that the complex C15 and C14 LLCs exhibit large unit cells, in which 12 or more ∼3-4 nm diameter micelles of multiple discrete sizes arrange into tetrahedral close packing arrangements with exceptional long-range translational order. The symmetry breaking that drives self-assembly into these low-symmetry LLC phases is rationalized in terms of a frustrated balance between maximizing counterion-mediated micellar cohesion within the ensemble of oil-swollen particles, while simultaneously optimizing local spherical particle symmetry to minimize molecular-level variations in surfactant solvation.

Original language	English (US)
Pages (from-to)	3226-3234
Number of pages	9
Journal	ACS nano
Volume	12
Issue number	4
DOIs	https://doi.org/10.1021/acsnano.7b07475
State	Published - Apr 24 2018
Externally published	Yes

Bibliographical note

Funding Information:
This work was supported by National Science Foundation grant CHE-1608115 and the University of Minnesota-Twin Cities. Synchrotron SAXS analyses were conducted at Sector 12 of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. Research reported in this publication was also supported by the Office of the Vice President of Research College of Science and Engineering, and the Department of Chemistry at the University of Minnesota.

Funding Information:
This work was supported by National Science Foundation grant CHE-1608115 and the University of Minnesota−Twin Cities. Synchrotron SAXS analyses were conducted at Sector 12 of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. Research reported in this publication was also supported by the Office of the Vice President of Research, College of Science and Engineering, and the Department of Chemistry at the University of Minnesota. We also thank G. Jackson and A. Jayaraman for assistance with analyses of the electron density maps and for helpful discussions.

Publisher Copyright:
© 2018 American Chemical Society.

Keywords

Frank-Kasper phases
liquid crystals
lyotropic phase
self-assembly
superlattices
surfactants

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title = "Micellar Mimicry of Intermetallic C14 and C15 Laves Phases by Aqueous Lyotropic Self-Assembly",

abstract = "Concentration-dependent supramolecular self-assembly of amphiphilic molecules in water furnishes a variety of nanostructured lyotropic liquid crystals (LLCs), which typically display high symmetry bicontinuous network and discontinuous micellar morphologies. Aqueous dispersions of soft spherical micelles derived from small molecule amphiphile hydration typically pack into exemplary body-centered cubic and closest-packed LLCs. However, investigations of hydrated mixtures of the ionic surfactant tetramethylammonium decanoate loaded with 40 wt % n-decane (TMADec-40) revealed the formation of a high symmetry bicontinuous double diamond LLC, as well as cubic C15 and hexagonal C14 Laves LLC phases that mirror the MgCu2 and MgZn2 intermetallic structure types, respectively. Detailed small-angle X-ray scattering analyses demonstrate that the complex C15 and C14 LLCs exhibit large unit cells, in which 12 or more ∼3-4 nm diameter micelles of multiple discrete sizes arrange into tetrahedral close packing arrangements with exceptional long-range translational order. The symmetry breaking that drives self-assembly into these low-symmetry LLC phases is rationalized in terms of a frustrated balance between maximizing counterion-mediated micellar cohesion within the ensemble of oil-swollen particles, while simultaneously optimizing local spherical particle symmetry to minimize molecular-level variations in surfactant solvation.",

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author = "Baez-Cotto, {Carlos M.} and Mahanthappa, {Mahesh K.}",

note = "Funding Information: This work was supported by National Science Foundation grant CHE-1608115 and the University of Minnesota-Twin Cities. Synchrotron SAXS analyses were conducted at Sector 12 of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. Research reported in this publication was also supported by the Office of the Vice President of Research College of Science and Engineering, and the Department of Chemistry at the University of Minnesota. Funding Information: This work was supported by National Science Foundation grant CHE-1608115 and the University of Minnesota−Twin Cities. Synchrotron SAXS analyses were conducted at Sector 12 of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. Research reported in this publication was also supported by the Office of the Vice President of Research, College of Science and Engineering, and the Department of Chemistry at the University of Minnesota. We also thank G. Jackson and A. Jayaraman for assistance with analyses of the electron density maps and for helpful discussions. Publisher Copyright: {\textcopyright} 2018 American Chemical Society.",

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Micellar Mimicry of Intermetallic C14 and C15 Laves Phases by Aqueous Lyotropic Self-Assembly

Abstract

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