scholarly journals Self-Assembly of an Equimolar Mixture of Liquid Crystals and Magnetic Nanoparticles

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 834
Author(s):  
Gaurav P. Shrivastav
Keyword(s):  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Self Assembly ◽  
Pair Correlation ◽  
Equimolar Mixture ◽  
Isotropic Phase ◽  
Fixed Temperature ◽  
Nematic Order ◽  
Smectic Phases ◽  
Dynamics Simulations

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found that the LCs show isotropic, nematic, and smectic phases when the mixture is compressed at a fixed temperature. The DSS form chain-like structures, which remain randomly oriented at low densities where the LCs are in the isotropic phase. At intermediate and high densities, the DSS chains align along the nematic and smectic directors of LCs. We found that the DSS inside a chain follow a ferromagnetic ordering. However, the mixture does not show a significant macroscopic magnetization. The extent of nematic order in the DSS remains very similar to the LCs in intermediate densities. At high densities, the DSS have a lower extent of nematic order than the LCs. The structure of the LC–DSS mixture was further analyzed via projected pair correlation functions for distances parallel and perpendicular to directors in the nematic and smectic phases.

scholarly journals Atomistic simulation studies of ionic cyanine dyes: self-assembly and aggregate formation in aqueous solution

2021 ◽  
Author(s):  
Gary Yu ◽  
Martin Walker ◽  
Mark Richard Wilson
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Liquid Crystals ◽  
Self Assembly ◽  
Atomistic Simulation ◽  
Large Scale ◽  
Cyanine Dyes ◽  
Simulation Studies ◽  
Aggregate Formation ◽  
Dynamics Simulations

Cyanine dyes are known to form large-scale aggregates of various morphologies via spontaneous self-assembly in aqueous solution, akin to chromonic liquid crystals. Atomistic molecular dynamics simulations have been performed on...

scholarly journals Study of Structural Changes in Nematic Liquid Crystals Doped with Magnetic Nanoparticles Using Surface Acoustic Waves

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1023
Author(s):  
Peter Bury ◽  
Marek Veveričík ◽  
František Černobila ◽  
Peter Kopčanský ◽  
Milan Timko ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Electric Fields ◽  
Acoustic Waves ◽  
Structural Changes ◽  
Surface Acoustic Waves ◽  
Theoretical Background ◽  
Isotropic Phase ◽  
Structure Of Nanoparticles

The surface acoustic waves (SAWs) were used to study the effect of magnetic nanoparticles on nematic liquid crystal (NLC) behavior in weak magnetic and electric fields. The measurement of the attenuation of SAW propagating along the interface between piezoelectric substrate and liquid crystal is showed as an effective tool to study processes of structural changes. The magnetic nanoparticles Fe3O4 of nanorod shape and different low volume concentration were added to the NLC (4-(trans-4′-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT)) during its isotropic phase. In contrast to undoped liquid crystals the distinctive different SAW attenuation responses induced by both magnetic and also electric fields in studied NLC samples were observed suggesting both structural changes and the orientational coupling between both magnetic and electric moments of nanoparticles and the director of the NLC molecules. Experimental measurements including the investigation under linearly increasing and/or jumped magnetic and electrical fields, respectively, as well as the investigation of temperature and time influences on structural changes were done. The investigation of the SAW anisotropy gives supplemental information about the internal structure of nanoparticles in investigated NLCs. In addition, some magneto-optical investigations were performed to support SAW results and study their stability and switching time. The analysis of observed SAW attenuation characteristics confirmed the role of concentration of magnetic nanoparticles on the resultant behavior of investigated NLC compounds. Obtained results are discussed within the context of previous ones. The theoretical background of the presented SAW investigation is introduced, too.

Effect of molecular solvents of varying polarity on the self-assembly of 1-n-dodecyl-3-methylimidazolium octylsulfate ionic liquid

2018 ◽  
Vol 17 (03) ◽  
pp. 1840004 ◽  
Author(s):  
Utkarsh Kapoor ◽  
Jindal K. Shah
Keyword(s):  
Ionic Liquid ◽  
Self Assembly ◽  
Large Scale ◽  
Structural Features ◽  
Nematic Order ◽  
Structure Factors ◽  
Dynamics Simulations ◽  
Multiple Domains ◽  
Molecular Solvents

Large-scale molecular dynamics simulations consisting of more than 88,000–106,000 atoms for approximately 250 ns (including equilibration and production) were conducted to assess the effect of polar, nonpolar and amphiphilic molecular solvents on the nanoscale structuring of 1-[Formula: see text]-dodecyl-3-methylimidazolium [C[Formula: see text]mim] octylsulfate [C8SO4] ionic liquid (IL). Water [H2O], [Formula: see text]-octane [C8H[Formula: see text]] and 1-octanol [C8H[Formula: see text]OH] are employed as examples of polar, nonpolar, and amphiphilic molecules, respectively. The results indicate that each of these molecular solvents modify the nanosegregation behavior of the ionic liquid in a unique way. Water induces a high order of structuring of the ionic liquid as indicated by extremely high nematic order parameter for the system. In addition, the morphology of the neat ionic liquid is transformed from layer-like to that of bilayer-like in which the polar and nonpolar domains alternate. The presence of water also causes the stretching of the nonpolar domain, thus, increasing its size. At the concentration examined in this work, [Formula: see text]-octane is found to be only partially miscible with the ionic liquid. The polar network is maintained; however, the continuous cationic nonpolar domain is split into multiple domains. [Formula: see text]-octane is accommodated in the ionic liquid nonpolar domain. Similarly, the amphiphilicity of 1-octanol leads to an increase in the number of cationic as well as anionic domains. The overall nonpolar domain length, however, remains nearly identical to that found for the pure ionic liquid. Additional characterization of structural features of the three systems is discussed in terms of one-dimensional number densities, nematic order parameters for the overall systems and their components and structure factors.

Liquid crystalline polymers: self-organization and assembly

1993 ◽  
Vol 344 (1672) ◽  
pp. 403-417 ◽  
Keyword(s):  
Liquid Crystals ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Side Chain ◽  
Simple Liquid ◽  
Crystalline Polymers ◽  
Nematic Order ◽  
Nematic State ◽  
Chain Conformations

Liquid crystal forming monomers, typically rods, can be polymerized to form long mesogenic molecules. In contrast to simple rods, these polymers often have internal degrees of freedom so that they display the subtle behaviour of both high polymers and simple liquid crystals. They can have the rod elements either concatenated as a back-bone to give main chain (MC), or pendant to a back-bone to give side chain (SC) liquid crystals, or both. The physics unique to liquid crystalline polymers (LCPS) comes from their shape being dependent on the state of nematic order. Simple systems remain molecular rods (or disks) on ordering whereas a chain extends or flattens (depending on whether or not the nematic order is prolate or oblate). New phenomena as a result of this occur in situations as disparate as networks and, it is predicted, in dielectric response. We examine both SC and MC LCPS and the mechanisms by which they order lyotropically (in solution) and therm otropically (in the melt). Various types of models will be discussed in general and then restricted to the therm otropic case, lyotropic systems being discussed in Lekkerkerker & Vroege (this volume). The transition to the ordered state is first order as in simple nematics. The main characteristics of this state are modified chain conformations and, additionally for side chain polymers, transitions between various novel competing nematic states. A form of self-assembly that is a delicate function of the nematic order is observed in transesterifying LCPS. The number of chain ends is conserved but material exchanged between chains according to whether they are in the isotropic or nematic state. We review a model of this type of self-assembly.

Microscopic ordering in smectic phases of liquid crystals

1990 ◽  
Vol 51 (18) ◽  
pp. 2015-2022 ◽  
Author(s):  
M. Zgonik ◽  
M. Rey-Lafon ◽  
C. Destrade ◽  
C. Leon ◽  
H.T. Nguyen
Keyword(s):  
Liquid Crystals ◽  
Smectic Phases

Evidence of two new ordered smectic phases in ferroelectric liquid crystals

1978 ◽  
Vol 39 (5) ◽  
pp. 548-553 ◽  
Author(s):  
J. Doucet ◽  
P. Keller ◽  
A.M. Levelut ◽  
P. Porquet
Keyword(s):  
Liquid Crystals ◽  
Ferroelectric Liquid Crystals ◽  
Smectic Phases

scholarly journals Polymer cyclization for the emergence of hierarchical nanostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chaojian Chen ◽  
Manjesh Kumar Singh ◽  
Katrin Wunderlich ◽  
Sean Harvey ◽  
Colette J. Whitfield ◽  
...  
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
Hierarchical Structures ◽  
Structural Similarity ◽  
Vital Role ◽  
Nanomaterial Synthesis ◽  
Wide Range ◽  
Linear Poly ◽  
Polymer Folding ◽  
Dynamics Simulations

AbstractThe creation of synthetic polymer nanoobjects with well-defined hierarchical structures is important for a wide range of applications such as nanomaterial synthesis, catalysis, and therapeutics. Inspired by the programmability and precise three-dimensional architectures of biomolecules, here we demonstrate the strategy of fabricating controlled hierarchical structures through self-assembly of folded synthetic polymers. Linear poly(2-hydroxyethyl methacrylate) of different lengths are folded into cyclic polymers and their self-assembly into hierarchical structures is elucidated by various experimental techniques and molecular dynamics simulations. Based on their structural similarity, macrocyclic brush polymers with amphiphilic block side chains are synthesized, which can self-assemble into wormlike and higher-ordered structures. Our work points out the vital role of polymer folding in macromolecular self-assembly and establishes a versatile approach for constructing biomimetic hierarchical assemblies.

Simulated Clustering Dynamics of Colloidal Magnetic Nanoparticles

Nanoscale ◽  
2021 ◽  
Author(s):  
Frederik Laust Durhuus ◽  
Lau Halkier Wandall ◽  
Mathias Hoeg Boisen ◽  
Mathias Kure ◽  
Marco Beleggia ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Self Assembly ◽  
Biomedical Applications ◽  
Magnetic Nanoparticle ◽  
Bottom Up ◽  
Novel Materials ◽  
Nanoparticle Clusters ◽  
Clustering Dynamics

Magnetically guided self-assembly of nanoparticles is a promising bottom-up method to fabricate novel materials and superstructures, such as, for example, magnetic nanoparticle clusters for biomedical applications. The existence of assembled...

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