Alejandro Rey - Academia.edu (original) (raw)

Papers by Alejandro Rey

Research paper thumbnail of Geometric modeling of phase ordering for the isotropic–smectic A phase transition

Frontiers in soft matter, May 21, 2024

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Research paper thumbnail of Pattern formation, structure and functionalities of wrinkled liquid crystal surfaces: A soft matter biomimicry platform

Frontiers in Soft Matter

This review presents an integrated theoretical and computational characterization and analysis of... more This review presents an integrated theoretical and computational characterization and analysis of surface pattern formation in chiral and achiral liquid crystal self-assembly and the mechanical/optical/tribological/tissue engineering surface functionalities that emerge from various wrinkling processes. Strategies to target surface patterns include linear, non-linear, multidirectional and multiscale wrinkling phenomena. The focus of the review is to show the unique surface structure-functionalities that emerge from anisotropic liquid crystal soft matter, eliminating or reducing the need of aggressive solvents, extreme pressure/temperature conditions, erosion and other surface morphing approaches. The surface pattern formation theoretical-modelling- computational results are then connected and validated with actual biological surfaces that are considered solid liquid crystal analogues, such as exocuticles of insects, fish scales, and flowers. A unique feature of the in silico surface ...

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Research paper thumbnail of Dynamic viscosity of methane hydrate systems from non-Einsteinian, plasma-functionalized carbon nanotube nanofluids

Nanoscale

Nanotubes may provide interfacial effects for viscosity reduction and align in the flow direction... more Nanotubes may provide interfacial effects for viscosity reduction and align in the flow direction. However, the graphene nanoflake surface area is only limited by its mean free path while nanotubes can entangle with each other.

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Research paper thumbnail of Chapter 2. Phase Diagrams, Phase Separation Mechanisms and Morphologies in Liquid Crystalline Materials: Principles and Theoretical Foundations

Soft Matter Series, 2019

Polymer–liquid crystal composites are heterogeneous materials that display a rich phase behaviour... more Polymer–liquid crystal composites are heterogeneous materials that display a rich phase behaviour and a variety of morphologies, and are typically used in electro-optical technological applications. This chapter presents a comprehensive general introduction to phase behaviour and morphologies of these materials. The fundamental physics underlying the formation of different morphologies is described, with a strong emphasis in how the trajectory in the phase diagram determines the phase separation mechanism and the emerging morphology. The effects of processing variables, chemical reaction and molecular structures on phase diagrams are rationalized through their effect on phase separation and diffusion. The theories, models and computations presented in this introductory chapter are a critical contribution to achieving desired functionalities by identifying the optimal processing conditions in these soft matter materials.

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Research paper thumbnail of Heat Capacity, Thermal Expansion Coefficient, and Grüneisen Parameter of CH4, CO2, and C2H6 Hydrates and Ice Ih via Density Functional Theory and Phonon Calculations

Crystal Growth & Design, 2020

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Research paper thumbnail of Structure evolution of spider silk liquid crystalline precursor material

Management of Natural Resources, Sustainable Development and Ecological Hazards, Nov 22, 2006

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Research paper thumbnail of THF Hydrates as Model Systems for Natural Gas Hydrates: Comparing Their Mechanical and Vibrational Properties

Industrial & Engineering Chemistry Research, 2019

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Research paper thumbnail of Infrared Spectra of Gas Hydrates from First-Principles

The Journal of Physical Chemistry B, 2019

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Research paper thumbnail of Characterization Methodology for Biological Plywoods Based on Characteristic Cross-Section Patterns

Journal of Renewable Materials, 2016

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Research paper thumbnail of Using linear viscoelasticity to assess flow-alignment of nematic liquid crystals

ABSTRACT

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Research paper thumbnail of Dendritic Patterns in Nematic Liquid Crystal Nanocomposites

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Research paper thumbnail of Theory and Simulation of Texture Transformations in Chiral Systems: Applications to Biological Fibrous Composites

MRS Proceedings, 2001

ABSTRACTNumerous studies [1-3] have shown that chiral biological structures share common properti... more ABSTRACTNumerous studies [1-3] have shown that chiral biological structures share common properties with liquids crystals, in particular a tendency to assemble in three-dimensional lattices very similar to that of chiral nematics. Biological fibrous composites are usually found in planar (film) and cylindrical (fibber) twist geometries. In this work, the formation process of the planar twist architecture is numerically investigated using a mesoscopic model based on the Landau-de Gennes theory of chiral nematic liquid crystals. The simulations and visualizations of the computed textures provide new information on some of the principles that govern the formation of chiral biological structures. It is found that a defect-free planar twist architecture arises from a chiral front propagation process with a fully relaxed wake.

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Research paper thumbnail of Optical Modeling of Twist Disclinations in Liquid Crystals

Frontiers in Optics, 2005

ABSTRACT Light propagation through liquid crystals (LCs) containing twist defects is studied usin... more ABSTRACT Light propagation through liquid crystals (LCs) containing twist defects is studied using FDTD method. The FDTD method provides accurate optical responses of the textured LCs when large spatial gradients in the optical axis are present.

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Research paper thumbnail of Pattern selection mechanism in mesophase carbon fibres

Modelling and Simulation in Materials Science and Engineering, 1997

ABSTRACT

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Research paper thumbnail of Structure and dynamics of biological liquid crystals

Liquid Crystals, 2013

A review of thermodynamic and flow liquid crystal models is presented and applied to a wide range... more A review of thermodynamic and flow liquid crystal models is presented and applied to a wide range of biological liquid crystals (BLCs), including helicoidal plywoods, biopolymer solutions and in vivo liquid crystals. The key characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials and the strong correspondence between different synthetic and biological materials is discussed. Viscoelastic models for nematic and chiral nematics are reviewed and discussed in terms of key parameters that facilitate understanding and quantitative information from experimental measurements. The range and consistency of the predictions demonstrates that the use of mesoscopic liquid crystal models is an efficient tool to develop the science and biomimetic applications of mesogenic biological materials.

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Research paper thumbnail of A Molecular and Thermodynamic View of the Assembly of Gold Nanoparticles in Nematic Liquid Crystal

Langmuir, 2013

The molecular interactions driving the assembly of gold nanoparticles (AuNPs) in a nematic liquid... more The molecular interactions driving the assembly of gold nanoparticles (AuNPs) in a nematic liquid crystal (LC) are directly detected by nuclear magnetic resonance (NMR) spectroscopy and thermodynamically analyzed. The orientational orders of the selectively deuterated LC matrix and AuNP ligands, each separately followed by variable temperature (2)H NMR as a function of particle concentration, were observed to be strongly correlated. The mechanism of the reversible formation of long-range, quasi-periodic nanoparticle structures is attributed to the coupling of the AuNP ligands to the LC matrix, inducing an isotropic-nematic biphasic state. Experimentally validated thermodynamic modeling shows that, in contrast to colloidal nematics that are dominated by elastic forces, nematic dispersions of nanoparticles self-organize through a subtle balance of entropic forces and excluded volume, interface-mediated mesogen and nanoparticle molecular interactions, and couplings between conserved and nonconserved order parameters. Fine-tuning of these interactions through ligand and mesogen chemistry, together with mesoscale modeling, provides a route for materials innovations by merging structured fluid physics and nanoscience.

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Research paper thumbnail of Linear and nonlinear viscoelasticity of discotic nematics under transient Poiseuille flows

Journal of Rheology, 2003

ABSTRACT

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Research paper thumbnail of Electroviscous cylinder–wall interactions

Journal of Colloid and Interface Science, 2006

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Research paper thumbnail of Complex Nanowrinkling in Chiral Liquid Crystal Surfaces: From Shaping Mechanisms to Geometric Statistics

Nanomaterials, May 4, 2022

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Research paper thumbnail of Atomistic-geometry inspired structure-composition-property relations of hydrogen sII hydrates

Scientific Reports

Gas hydrates are crystalline inclusion compounds formed by trapping gas molecules inside water ca... more Gas hydrates are crystalline inclusion compounds formed by trapping gas molecules inside water cages at high pressures and low temperatures. Hydrates are promising materials for hydrogen storage, but their potential depends on understanding their mechanical properties. This work integrates density functional theory (DFT) simulations with a geometry-inspired composite material model to explore the bulk moduli of structure II hydrogen hydrates subjected to pressure loads of − 0.2 to 3 GPa, representative of the hydrogen hydrate formation conditions. Our findings reveal that structure II hydrate comprises a bi-continuous composite of small and large cages with nearly equal volume fractions. The bulk modulus increases with rising pressure but decreases with increasing composition. Notably, these results align closely with the ideal laws of mixtures, especially at low pressures and compositions, where cage interactions are minimal. This integrated DFT-laws of mixtures methodology provide...

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Research paper thumbnail of Geometric modeling of phase ordering for the isotropic–smectic A phase transition

Frontiers in soft matter, May 21, 2024

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Pattern formation, structure and functionalities of wrinkled liquid crystal surfaces: A soft matter biomimicry platform

Frontiers in Soft Matter

This review presents an integrated theoretical and computational characterization and analysis of... more This review presents an integrated theoretical and computational characterization and analysis of surface pattern formation in chiral and achiral liquid crystal self-assembly and the mechanical/optical/tribological/tissue engineering surface functionalities that emerge from various wrinkling processes. Strategies to target surface patterns include linear, non-linear, multidirectional and multiscale wrinkling phenomena. The focus of the review is to show the unique surface structure-functionalities that emerge from anisotropic liquid crystal soft matter, eliminating or reducing the need of aggressive solvents, extreme pressure/temperature conditions, erosion and other surface morphing approaches. The surface pattern formation theoretical-modelling- computational results are then connected and validated with actual biological surfaces that are considered solid liquid crystal analogues, such as exocuticles of insects, fish scales, and flowers. A unique feature of the in silico surface ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Dynamic viscosity of methane hydrate systems from non-Einsteinian, plasma-functionalized carbon nanotube nanofluids

Nanoscale

Nanotubes may provide interfacial effects for viscosity reduction and align in the flow direction... more Nanotubes may provide interfacial effects for viscosity reduction and align in the flow direction. However, the graphene nanoflake surface area is only limited by its mean free path while nanotubes can entangle with each other.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Chapter 2. Phase Diagrams, Phase Separation Mechanisms and Morphologies in Liquid Crystalline Materials: Principles and Theoretical Foundations

Soft Matter Series, 2019

Polymer–liquid crystal composites are heterogeneous materials that display a rich phase behaviour... more Polymer–liquid crystal composites are heterogeneous materials that display a rich phase behaviour and a variety of morphologies, and are typically used in electro-optical technological applications. This chapter presents a comprehensive general introduction to phase behaviour and morphologies of these materials. The fundamental physics underlying the formation of different morphologies is described, with a strong emphasis in how the trajectory in the phase diagram determines the phase separation mechanism and the emerging morphology. The effects of processing variables, chemical reaction and molecular structures on phase diagrams are rationalized through their effect on phase separation and diffusion. The theories, models and computations presented in this introductory chapter are a critical contribution to achieving desired functionalities by identifying the optimal processing conditions in these soft matter materials.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Heat Capacity, Thermal Expansion Coefficient, and Grüneisen Parameter of CH4, CO2, and C2H6 Hydrates and Ice Ih via Density Functional Theory and Phonon Calculations

Crystal Growth & Design, 2020

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Structure evolution of spider silk liquid crystalline precursor material

Management of Natural Resources, Sustainable Development and Ecological Hazards, Nov 22, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of THF Hydrates as Model Systems for Natural Gas Hydrates: Comparing Their Mechanical and Vibrational Properties

Industrial & Engineering Chemistry Research, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Infrared Spectra of Gas Hydrates from First-Principles

The Journal of Physical Chemistry B, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Characterization Methodology for Biological Plywoods Based on Characteristic Cross-Section Patterns

Journal of Renewable Materials, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Using linear viscoelasticity to assess flow-alignment of nematic liquid crystals

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Dendritic Patterns in Nematic Liquid Crystal Nanocomposites

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Theory and Simulation of Texture Transformations in Chiral Systems: Applications to Biological Fibrous Composites

MRS Proceedings, 2001

ABSTRACTNumerous studies [1-3] have shown that chiral biological structures share common properti... more ABSTRACTNumerous studies [1-3] have shown that chiral biological structures share common properties with liquids crystals, in particular a tendency to assemble in three-dimensional lattices very similar to that of chiral nematics. Biological fibrous composites are usually found in planar (film) and cylindrical (fibber) twist geometries. In this work, the formation process of the planar twist architecture is numerically investigated using a mesoscopic model based on the Landau-de Gennes theory of chiral nematic liquid crystals. The simulations and visualizations of the computed textures provide new information on some of the principles that govern the formation of chiral biological structures. It is found that a defect-free planar twist architecture arises from a chiral front propagation process with a fully relaxed wake.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optical Modeling of Twist Disclinations in Liquid Crystals

Frontiers in Optics, 2005

ABSTRACT Light propagation through liquid crystals (LCs) containing twist defects is studied usin... more ABSTRACT Light propagation through liquid crystals (LCs) containing twist defects is studied using FDTD method. The FDTD method provides accurate optical responses of the textured LCs when large spatial gradients in the optical axis are present.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Pattern selection mechanism in mesophase carbon fibres

Modelling and Simulation in Materials Science and Engineering, 1997

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Structure and dynamics of biological liquid crystals

Liquid Crystals, 2013

A review of thermodynamic and flow liquid crystal models is presented and applied to a wide range... more A review of thermodynamic and flow liquid crystal models is presented and applied to a wide range of biological liquid crystals (BLCs), including helicoidal plywoods, biopolymer solutions and in vivo liquid crystals. The key characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials and the strong correspondence between different synthetic and biological materials is discussed. Viscoelastic models for nematic and chiral nematics are reviewed and discussed in terms of key parameters that facilitate understanding and quantitative information from experimental measurements. The range and consistency of the predictions demonstrates that the use of mesoscopic liquid crystal models is an efficient tool to develop the science and biomimetic applications of mesogenic biological materials.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Molecular and Thermodynamic View of the Assembly of Gold Nanoparticles in Nematic Liquid Crystal

Langmuir, 2013

The molecular interactions driving the assembly of gold nanoparticles (AuNPs) in a nematic liquid... more The molecular interactions driving the assembly of gold nanoparticles (AuNPs) in a nematic liquid crystal (LC) are directly detected by nuclear magnetic resonance (NMR) spectroscopy and thermodynamically analyzed. The orientational orders of the selectively deuterated LC matrix and AuNP ligands, each separately followed by variable temperature (2)H NMR as a function of particle concentration, were observed to be strongly correlated. The mechanism of the reversible formation of long-range, quasi-periodic nanoparticle structures is attributed to the coupling of the AuNP ligands to the LC matrix, inducing an isotropic-nematic biphasic state. Experimentally validated thermodynamic modeling shows that, in contrast to colloidal nematics that are dominated by elastic forces, nematic dispersions of nanoparticles self-organize through a subtle balance of entropic forces and excluded volume, interface-mediated mesogen and nanoparticle molecular interactions, and couplings between conserved and nonconserved order parameters. Fine-tuning of these interactions through ligand and mesogen chemistry, together with mesoscale modeling, provides a route for materials innovations by merging structured fluid physics and nanoscience.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Linear and nonlinear viscoelasticity of discotic nematics under transient Poiseuille flows

Journal of Rheology, 2003

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Electroviscous cylinder–wall interactions

Journal of Colloid and Interface Science, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Complex Nanowrinkling in Chiral Liquid Crystal Surfaces: From Shaping Mechanisms to Geometric Statistics

Nanomaterials, May 4, 2022

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Atomistic-geometry inspired structure-composition-property relations of hydrogen sII hydrates

Scientific Reports

Gas hydrates are crystalline inclusion compounds formed by trapping gas molecules inside water ca... more Gas hydrates are crystalline inclusion compounds formed by trapping gas molecules inside water cages at high pressures and low temperatures. Hydrates are promising materials for hydrogen storage, but their potential depends on understanding their mechanical properties. This work integrates density functional theory (DFT) simulations with a geometry-inspired composite material model to explore the bulk moduli of structure II hydrogen hydrates subjected to pressure loads of − 0.2 to 3 GPa, representative of the hydrogen hydrate formation conditions. Our findings reveal that structure II hydrate comprises a bi-continuous composite of small and large cages with nearly equal volume fractions. The bulk modulus increases with rising pressure but decreases with increasing composition. Notably, these results align closely with the ideal laws of mixtures, especially at low pressures and compositions, where cage interactions are minimal. This integrated DFT-laws of mixtures methodology provide...

Bookmarks Related papers MentionsView impact