Relation between the grafting density of liquid crystal macromolecule and the symmetry of self-assembled bulk phase: coarse-grained molecular dynamics study

Ilnytskyi, Jaroslav

doi:10.5488/cmp.16.43004

Cited by 10 publications

(41 citation statements)

References 36 publications

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“…The model for a MP with laterally attached mesogens is based on its counterpart with terminal attachment described in detail in references [17,18]. The central sphere represents a core (be it a gold nanoparticle or a dendritic core) decorated by grafting N ch = 32 chains to it.…”

Section: Resultsmentioning

confidence: 99%

Novel morphologies for laterally decorated metaparticles: molecular dynamics simulation

Slyusarchuk¹,

Ilnytskyi²

2014

Condens. Matter Phys.

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We consider a mesoscale model for nano-sized metaparticles (MPs) composed of a central sphere decorated by polymer chains with laterally attached spherocylinder. The latter mimics the mesogenic (e.g., cyanobiphenyl) group. Molecular dynamics simulations of 100 MPs reveal the existence of two novel morphologies: uCol h (hexagonal columnar arrangement of MPs with strong uniaxial order of mesogens collinear to the columns axis) and wCol h [the same arrangement of MPs but with weak or no liquid crystalline (LC) order]. Collinearity of the LC director and the columnar axis in uCol h morphology indicates its potentially different opto-mechanical response to an external perturbation as compared to the columnar phase for the terminally attached mesogens. Preliminary analysis of the structures of both phases is performed by studying the order parameters and by visualisation of the MPs arrangements. Different mechanisms for the mesogens reorientation are pointed out for the cases of their terminal and lateral attachment. MotivationColloid particles, polymers and LC molecules represent main building blocks of soft matter physics [1]. When two or more of such blocks are combined into a MP, the latter forms a meta-material that exhibits a range of new morphologies and new effects that are not observed for any of its pure constituents. Examples to mention are: LC elastomers, LC dendrimers, decorated nanoparticles and others [2][3][4][5][6][7], all of these having already found a number of applications in thermo-and photo-controlled elasticity, plasmonic resonance, photonics and medicine. Most applications rely on the symmetry of the equilibrium morphology, in which each constituent is "responsible" for particular property of a meta-material. For instance, its elasticity is usually controlled by a polymer subsystem, optical properties are governed by both the behaviour of mesogens and the arrangement of gold nanoparticles (if any). Therefore, the type of mutual arrangement of the constituent parts is crucial regarding the new potential applications of each particular meta-material.Let us concentrate on the MPs built out of a spherical core decorated by polymer chains (spacers) each ending by a mesogen. The core mimics either a solid nanoparticle (e.g., gold nanoparticle [6,7]) or averaged in time shape of a dendritic scaffold [4,5]. It was found experimentally that the most important aspects of decoration are as follows: the surface density of mesogens on the outer shell of MP, the length of a spacer, and the exact way mesogens are attached chemically to the spacer [4][5][6][7][8][9][10][11]. In particular, both terminal and lateral attachment can be realised chemically [4,5,[8][9][10][11] [depicted schematically in figure 1 (a) and (b)] and the difference between the morphologies observed in these two cases are in the focus of this study.

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Section: Resultsmentioning

confidence: 99%

Novel morphologies for laterally decorated metaparticles: molecular dynamics simulation

Slyusarchuk¹,

Ilnytskyi²

2014

Condens. Matter Phys.

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“…More discussion can be found elsewhere. [31][32][33] To cover various types of decoration of GNP by LC ligands, we developed a set of new coarse-grained models classified in Fig. 1.…”

Section: Figmentioning

confidence: 99%

“…These extend the model considered in Refs. 31,32,34,35,38 by applying additional constraints to the movement of ligands with respect to the GNP, by employing the approach from Refs. 36,37 Let us first describe the models shown in Fig.…”

Section: Figmentioning

confidence: 99%

“…All simulations are performed in the NV T ensemble at the temperature of T = 480 K. This choice is based on a number of previous studies on the self-assembly of similar coarse-grained models. 31,32,34,38 In particular, the liquid crystallinity in such models disappears at approximately 500 − 510 K and the temperatures within the range of 480 − 490K are found to be best suited for the LC-based aggregation 34 or spontaneous self-assembly. 38 This is exactly the range of temperatures that are high enough to ensure sufficient mobility of PGNPs and, instantaneously, are not too high to hamper their liquid crystallinity, which is the principal mechanism for gelation of PGNPs.…”

Section: Figmentioning

confidence: 99%

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Gelation of patchy ligand shell nanoparticles decorated by liquid-crystalline ligands: computer simulation study

2018

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We consider the coarse-grained modelling of patchy ligand shell nanoparticles with liquid crystalline ligands. The cases of two, three, four and six symmetrically arranged patches of ligands are discussed, as well as the cases of their equatorial and icosahedral arrangement. A solution of decorated nanoparticles is considered within a slit-like pore with solid walls and the interior filled by a polar solvent. The ligands form physical cross-links between the nanoparticles due to strong liquid crystalline interaction, turning the solution into a gel-like structure. Gelation is carried out repeatedly starting each time from a freshly equilibrated dispersed state of nanoparticles. The gelation dynamics and the range of network characteristics of the gel are examined, depending on the type of patchy decoration and on the solution density. Emphasis is given to the theoretical prediction of the type of decoration and the solution density most suitable for producing a uniformly cross-linked and highly elastic gel structure.

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“…29 It has already been used in a number of studies of LC oligomers and macromolecules. [30][31][32][33][34] In principle, the coarse-grained nature of this model should allow one to explore larger system sizes, required for the description of certain defect topologies and has a potential to speed up the equilibration of the system. We perform a thorough analysis of the applicability of this soft-core spherocylinder model for the simulation of defects around an isolated spherical colloid particle.…”

Section: Introductionmentioning

confidence: 99%

Topological defects around a spherical nanoparticle in nematic liquid crystal: Coarse-grained molecular dynamics simulations

Ilnytskyi

Trokhymchuk

Schoen

2014

The Journal of Chemical Physics

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We consider the applicability of coarse-grained molecular dynamics for the simulation of defects in a nematic liquid crystal around a colloidal particle. Two types of colloids are considered, a soft colloid resembling a liquid crystal dendrimer or a similar macromolecule. In addition, a decorated colloid is used which could represent a gold nanoparticle with mesogen-modified surface. For both models we consider homeotropic and tangential anchoring. Precise control of the easy axis on the colloid's surface enables us to focus on specific planar arrangements in the case of a decorated colloid. The nematic phase is modelled explicitly via soft spherocylinders interacting through a potential, suggested by Lintuvuori and Wilson [J. Chem. Phys. 128, 044906 (2008)]. Properties of the nematic phase are studied by computing the Frank elastic constants. In addition, estimates for the nematic-isotropic transition and the coherence length allow us to establish a relation between energy and length scales with respect to experimental systems. Both models exhibit similar defect topologies, namely, that of a Saturn ring and a boojum-type of defect for homeotropic and tangential surface anchoring, respectively. In the decorated colloid model we tune the anchoring strength through the density of the mesogenic shell on the surface. We also found the biaxial boojum defect for the special case of longitudinal planar anchoring. The study demonstrates the potential of coarse-grained simulation methods for studying defects in liquid crystals.

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Relation between the grafting density of liquid crystal macromolecule and the symmetry of self-assembled bulk phase: coarse-grained molecular dynamics study

Cited by 10 publications

References 36 publications

Novel morphologies for laterally decorated metaparticles: molecular dynamics simulation

Novel morphologies for laterally decorated metaparticles: molecular dynamics simulation

Gelation of patchy ligand shell nanoparticles decorated by liquid-crystalline ligands: computer simulation study

Topological defects around a spherical nanoparticle in nematic liquid crystal: Coarse-grained molecular dynamics simulations

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