A dissipative particle dynamics description of liquid-crystalline phases. I. Methodology and applications

Levine, Y.K.; Gomes, Alexandre E.; Martins, A. F.; Polimeno, Antonino

doi:10.1063/1.1879852

Cited by 41 publications

(38 citation statements)

References 38 publications

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“…Nanorods are simulated as rigid bodies in the NVE ensemble using an algorithm by Miller et al 57 Their correct temperature is maintained through the interactions with the thermostated polymeric DPD liquid surrounding them. It is worth noting that semi-rigid mesogens can be also simulated with DPD using an additional spring force between their first and last particles 58 or by introducing angle potentials. 59 For the sake of comparison we perform some simulations by replacing nanorods with flexible chains consisting of N R = 5 particles of R type.…”

Section: A Dissipative Particle Dynamicsmentioning

confidence: 99%

Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory

Berezkin

Kudryavtsev

Gorkunov

et al. 2017

The Journal of Chemical Physics

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Short title: Ordering of anisotropic nanoparticles: Simulations and theory a) Corresponding author. Electronic mail: yar@ips.ac.ru 2 ABSTRACT Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for nonselective nanorods near the domain boundary. In this case the nanorods have a certain tendency to align parallel to the interface in the boundary region and perpendicular to it inside the domains. Similar orientation ordering of spherical nanoparticles located at the lamellar interface is predicted by the molecular theory which takes into account that the nanoparticles interact with monomer units via both isotropic and anisotropic potentials. Computer simulations enable one to study the effects of the nanorod concentration, length, stiffness, and selectivity of their interactions with the copolymer components on the phase stability and orientational order of nanoparticles. If the volume fraction of the nanorods is lower than 0.1, they have no effect on the copolymer transition from the disordered state into a lamellar microstructure. Increasing nanorod concentration or nanorod length results in clustering of the nanorods and eventually leads to a macrophase separation, whereas the copolymer preserves its lamellar morphology. Segregated nanorods of length close to the width of the diblock copolymer domains are stacked side by side into smectic layers that fill domain space. Thus, spontaneous organization and orientation of nanorods leads to a spatial modulation of anisotropic composite properties creating an opportunity to align block copolymers by external fields which may be important for various applications.

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Section: A Dissipative Particle Dynamicsmentioning

confidence: 99%

Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory

Berezkin

Kudryavtsev

Gorkunov

et al. 2017

The Journal of Chemical Physics

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“…In the case of the A 1 B 3 polymer a lamellar phase is observed at T * = 1.0; the low value of the order parameter and the fact that the middle eigenvalue of the order tensor (S 0 ) is significantly larger than 0 suggests that the polymer chains within each layer are well ordered but the orientation of each layer is independent of the others. It is noticeable that none of the polymers studied exhibits a nematic phase, which has been observed in DPD simulations of rigid and semi-rigid rods [42,36]. It is possible that the transition to positionally ordered phases preempts the isotropic-nematic transition.…”

Section: Resultsmentioning

confidence: 93%

“…Unlike in experimental studies, a nematic phase is not observed in any of the systems considered in this work. Nematic phases have been observed in DPD simulations [36] and it is likely that in the systems studied the nematic window is vanishingly small or that translational ordering preempts the formation of the nematic phase.…”

Section: Discussionmentioning

confidence: 99%

“…For bonds between adjacent beads k r = 4kǫ/r 2 c and r eq ij = 0. In order to preserve the rigidity of the backbone an additional bond is added between the first and last backbone beads [36], with k r = 10ǫ/r 2 c and r eq j = 15.2r c . k θ = 20k B T for all angles, with the linear form being used for all angles apart from AAB angles, which use the harmonic form with θ eq j = 90…”

Section: Simulation Modelmentioning

confidence: 99%

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Molecular structure and phase behaviour of hairy-rod polymers

Cheung

Troisi

2009

Phys. Chem. Chem. Phys.

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Using dissipative particle dynamics simulations the relationship between molecular architecture and phase behaviour in model hairy-rod polymers is studied. In agreement with experimental and theoretical studies the phase behaviour is controlled by changes to the molecular structure, particularly the sidechain length and density, and the molecular interactions. For dense sidechains a lamellar structure is found, which becomes an inverted cylindrical phase when the sidechain density is lowered. The ordered phases become more stable on increasing sidechain length and on increasing the repulsion strength between the backbone and sidechains. In the absence of torsional potentials the structures are double-walled, i.e. layers are two polymer backbones thick, while single-walled structures are observed for polymers with torsional potentials

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“…Inherent in the DPD work is the employment of underlying ultra-soft-potentials, allowing particles to pass through each other and thereby improving equilibration times greatly. Such technique have recently been exploited by Levine et al [151] and Gomes and co-workers [152] to study nematic and smectic mesophases.…”

Section: Helical Twisting Powersmentioning

confidence: 99%

Progress in computer simulations of liquid crystals

Wilson

2005

International Reviews in Physical Chemistry

139

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This article reviews some of the recent progress in the simulation of liquid crystals across a range of length and time scales. Simulators now have an extensive range of models at their disposal, ranging from fully atomistic studies where each atom is represented in a simulation, via hard or soft anisotropic potentials, to lattice models and director-based simulation methods. Each of these provide access to different phenomena. The progress towards accurate atomistic modelling of nematics is discussed in detail, pointing to improvements in force fields made recently and discussing the progress towards accurate prediction of material properties. Three material properties are discussed in detail: elastic constants, rotational viscosity and helical twisting powers. The simulation methods that can be employed to extract such properties are reviewed and the insights provided by recent results from atomistic and coarse-grained models are discussed. The article points also to the recent success of coarse-grained modelling in helping to understand the structure of complex macromolecular liquid crystals: liquid crystal polymers and liquid crystal dendrimers in which the macromolecules contain different types of interaction site. Finally, it is worth noting that throughout Nature liquid crystals occur as the archetypal self-assembled materials; able to form well-defined self-organized structures, which are often ordered at the nanoscale. With this in mind, some perspectives on the future use of these materials are presented, with suggestions for how liquid crystal simulation can be used to help in the design of the next generation of nanoscale devices.

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A dissipative particle dynamics description of liquid-crystalline phases. I. Methodology and applications

Cited by 41 publications

References 38 publications

Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory

Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory

Molecular structure and phase behaviour of hairy-rod polymers

Progress in computer simulations of liquid crystals

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