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Wei X, Bradley LC. Accessing Thin Film Wetting Regimes during Polymer Growth by Initiated Chemical Vapor Deposition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11550-11556. [PMID: 36108132 DOI: 10.1021/acs.langmuir.2c00979] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We investigate the growth of a fluorinated polymer via initiated chemical vapor deposition onto a suite of isotropic and mesogenic liquids with a range of refractive indices. The polymer morphology at fluid interfaces was found to deviate from conformal films predicted by the positive spreading coefficient, and the resulting morphology is attributed to long-range van der Waals interactions during the deposition process. Experiments systematically vary the deposition conditions and compare the liquid phase (isotropic or nematic) to evaluate the effect of kinetic factors and the liquid substrate phase on the interfacial polymer morphology and spatial organization.
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Affiliation(s)
- Xiaoshuang Wei
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Laura C Bradley
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
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Senyuk B, Meng C, Smalyukh II. Design and Preparation of Nematic Colloidal Particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:9099-9118. [PMID: 35866261 DOI: 10.1021/acs.langmuir.2c00611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Colloidal systems are abundant in technology, in biomedical settings, and in our daily life. The so-called "colloidal atoms" paradigm exploits interparticle interactions to self-assemble colloidal analogs of atomic and molecular crystals, liquid crystal glasses, and other types of condensed matter from nanometer- or micrometer-sized colloidal building blocks. Nematic colloids, which comprise colloidal particles dispersed within an anisotropic nematic fluid host medium, provide a particularly rich variety of physical behaviors at the mesoscale, not only matching but even exceeding the diversity of structural and phase behavior in conventional atomic and molecular systems. This feature article, using primarily examples of works from our own group, highlights recent developments in the design, fabrication, and self-assembly of nematic colloidal particles, including the capabilities of preprogramming their behavior by controlling the particle's surface boundary conditions for liquid crystal molecules at the colloidal surfaces as well as by defining the shape and topology of the colloidal particles. Recent progress in defining particle-induced defects, elastic multipoles, self-assembly, and dynamics is discussed along with open issues and challenges within this research field.
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Affiliation(s)
- Bohdan Senyuk
- Department of Physics, University of Colorado, Boulder, Colorado 80309, United States
| | - Cuiling Meng
- Department of Physics, University of Colorado, Boulder, Colorado 80309, United States
| | - Ivan I Smalyukh
- Department of Physics, University of Colorado, Boulder, Colorado 80309, United States
- Department of Electrical, Computer and Energy Engineering, University of Colorado, Boulder, Colorado 80309, United States
- Soft Materials Research Center and Materials Science and Engineering Program, University of Colorado, Boulder, Colorado 80309, United States
- Chemical Physics Program, Departments of Chemistry and Physics, University of Colorado, Boulder, Colorado 80309, United States
- Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado, Boulder, Colorado 80309, United States
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Junot G, Wei X, Ortín J, Golestanian R, Wang Y, Tierno P, Meng F. Elastically-mediated collective organisation of magnetic microparticles. SOFT MATTER 2022; 18:5171-5176. [PMID: 35802129 DOI: 10.1039/d2sm00565d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Gels are soft elastic materials made of a three-dimensional cross-linked polymer network and featuring both elastic and dissipative responses under external mechanical stimuli. Here we investigate how such gels mediate the organization of embedded magnetic microparticles when driven by an external field. By constructing a continuum theory, we demonstrate that the collective dynamics of the embedded particles result from the delicate balance between magnetic dipole-dipole interactions, thermal fluctuations and elasticity of the polymer network, verified by our experiments. The proposed model could be extended to other soft magnetic composites in order to predict how the elastic interactions mediate the aggregation of the embedded elements, fostering technological implications for multifunctional hydrogel materials.
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Affiliation(s)
- Gaspard Junot
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Catalonia, Spain.
| | - Xuefeng Wei
- CAS Key Laboratory for Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, China
| | - Jordi Ortín
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Catalonia, Spain.
- Universitat de Barcelona Institute of Complex Systems, 08028, Barcelona, Catalonia, Spain
| | - Ramin Golestanian
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077, Göttingen, Germany
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Yanting Wang
- CAS Key Laboratory for Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, China
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, 325001, China
| | - Pietro Tierno
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Catalonia, Spain.
- Universitat de Barcelona Institute of Complex Systems, 08028, Barcelona, Catalonia, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028, Spain
| | - Fanlong Meng
- CAS Key Laboratory for Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, China
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, 325001, China
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Loudet JC, Choudhury A, Qiu M, Feng JJ. Particle trapped at the isotropic-nematic liquid crystal interface: Elastocapillary phenomena and drag forces. Phys Rev E 2022; 105:044607. [PMID: 35590681 DOI: 10.1103/physreve.105.044607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 04/04/2022] [Indexed: 06/15/2023]
Abstract
We present numerical simulations of a particle trapped at the isotropic-nematic liquid crystal (Iso-N) interface. We use our recent model, based on a phase-field approach [see Qiu et al., Phys. Rev. E 103, 022706 (2021)10.1103/PhysRevE.103.022706], to couple the capillary forces acting on the interface with the elastic stresses in the nematic phase along with topological defects. A range of floating configurations are first investigated as a function of the contact angle and various anchoring conditions at the fluid interface. The results show that the response of the system is driven by the existence of an anchoring conflict at the contact line. Substantial particle displacements and/or interfacial deformations may occur in this case even for moderate anchoring strengths. These findings highlight the coupling between elastic and capillary forces. In a second part, we compute drag forces exerted on a particle that moves along the Iso-N interface for several contact angles and a moderate Ericksen number. Because of the coupling between the velocity and order parameter fields, topological defects are swept downstream of the particle by the flow and sometimes escape from the particle or merge with the interface. We also find linear force-velocity laws, with drag forces at the Iso-N interface being slightly greater than their isotropic counterparts due to director distortions. We discuss these results in light of past studies on the behavior of particles being dragged in the bulk of a liquid crystal matrix.
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Affiliation(s)
- J-C Loudet
- Université de Bordeaux, CNRS, Centre de Recherche Paul Pascal (UMR 5031), 33600 Pessac, France
| | - A Choudhury
- Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, 502284 Telangana, India
- University of British Columbia, Department of Mathematics, Vancouver, BC, Canada V6T 1Z2
| | - M Qiu
- Laboratoire de Physique, École Normale Supérieure, 75005 Paris, France
| | - J J Feng
- University of British Columbia, Department of Mathematics, Vancouver, BC, Canada V6T 1Z2
- University of British Columbia, Department of Chemical and Biological Engineering, Vancouver, BC, Canada V6T 1Z3
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Xie Q, Harting J. Controllable Capillary Assembly of Magnetic Ellipsoidal Janus Particles into Tunable Rings, Chains and Hexagonal Lattices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006390. [PMID: 33448100 DOI: 10.1002/adma.202006390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 11/17/2020] [Indexed: 06/12/2023]
Abstract
Colloidal assembly at fluid interfaces has a great potential for the bottom-up fabrication of novel structured materials. However, challenges remain in realizing controllable and tunable assembly of particles into diverse structures. Herein, the capillary assembly of magnetic ellipsoidal Janus particles at a fluid-fluid interface is reported. Depending on their tilt angle, that is, the angle the particle main axis forms with the fluid interface, these particles deform the interface and generate capillary dipoles or hexapoles. Driven by capillary interactions, multiple particles thus assemble into chain-, hexagonal-lattice-, and ring-like structures, which can be actively controlled by applying an external magnetic field. A field-strength phase diagram is predicted in which various structures are present as stable states. Owing to the diversity, controllability, and tunability of assembled structures, magnetic ellipsoidal Janus particles at fluid interfaces could therefore serve as versatile building blocks for novel materials.
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Affiliation(s)
- Qingguang Xie
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB, Eindhoven, The Netherlands
| | - Jens Harting
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Fürther Str. 248, 90429, Nürnberg, Germany
- Department of Chemical and Biological Engineering and Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fürther Str. 248, 90429, Nürnberg, Germany
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Khadem SA, Bagnani M, Mezzenga R, Rey AD. Relaxation dynamics in bio-colloidal cholesteric liquid crystals confined to cylindrical geometry. Nat Commun 2020; 11:4616. [PMID: 32934229 PMCID: PMC7493995 DOI: 10.1038/s41467-020-18421-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 08/12/2020] [Indexed: 12/22/2022] Open
Abstract
Para-nematic phases, induced by unwinding chiral helices, spontaneously relax to a chiral ground state through phase ordering dynamics that are of great interest and crucial for applications such as stimuli-responsive and biomimetic engineering. In this work, we characterize the cholesteric phase relaxation behaviors of β-lactoglobulin amyloid fibrils and cellulose nanocrystals confined into cylindrical capillaries, uncovering two different equilibration pathways. The integration of experimental measurements and theoretical predictions reveals the starkly distinct underlying mechanism behind the relaxation dynamics of β-lactoglobulin amyloid fibrils, characterized by slow equilibration achieved through consecutive sigmoidal-like steps, and of cellulose nanocrystals, characterized by fast equilibration obtained through smooth relaxation dynamics. Particularly, the specific relaxation behaviors are shown to emerge from the order parameter of the unwound cholesteric medium, which depends on chirality and elasticity. The experimental findings are supported by direct numerical simulations, allowing to establish hard-to-measure viscoelastic properties without applying magnetic or electric fields.
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Affiliation(s)
- Sayyed Ahmad Khadem
- Department of Chemical Engineering, McGill University, Montreal, QC, H3A 2B2, Canada
- Quebec Centre for Advanced Materials, Canada (QCAM/CQMF), Montreal, QC, H3A 2K6, Canada
| | - Massimo Bagnani
- Department of Health Sciences and Technology, ETH Zurich, Schmelzbergstrasse 9, Zurich, 8092, Switzerland
| | - Raffaele Mezzenga
- Department of Health Sciences and Technology, ETH Zurich, Schmelzbergstrasse 9, Zurich, 8092, Switzerland
- Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, Zurich, 8093, Switzerland
| | - Alejandro D Rey
- Department of Chemical Engineering, McGill University, Montreal, QC, H3A 2B2, Canada.
- Quebec Centre for Advanced Materials, Canada (QCAM/CQMF), Montreal, QC, H3A 2K6, Canada.
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Wei X, Sbalbi N, Bradley LC. Nematic colloids at liquid crystal-air interfaces via photopolymerization. SOFT MATTER 2020; 16:9121-9127. [PMID: 32914808 DOI: 10.1039/d0sm01311k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We demonstrate the preparation of colloidal crystals at nematic liquid crystal-air interfaces by simultaneous photopolymerization and assembly. Polymer colloids are produced by polymerization-induced phase separation of 2-hydroxyethyl methacrylate in the non-reactive liquid crystal (LC) 4-cyano-4'-pentylbiphenyl (5CB) using an open-cell setup. Colloids adsorbed to the nematic 5CB-air interface form non-close-packed hexagonal crystals that cover the entire interface area. We examine the mechanism of growth and assembly for the preparation of LC-templated interfacial colloidal superstructures.
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Affiliation(s)
- Xiaoshuang Wei
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
| | - Nicholas Sbalbi
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
| | - Laura C Bradley
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
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