Effect of the flexibility on the phase transition of polymeric liquid crystals

Bosch, A. ten; Maïssa, P.; Sixou, P.

doi:10.1016/0375-9601(83)90723-5

Cited by 33 publications

(5 citation statements)

References 10 publications

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“…The above observation agrees with earlier mean field studies of polymer nematics [28,44,42,[72][73][74] and the ordered-fluid transition in lipid membranes [75]. The theoretical treatments of Wang and Warner [73] and of Rusakov and Shliomis [42] are particularly detailed as regards the effect of the molecular weight and the temperature of the isotropic-nematic transition.…”

Section: The Isotropic-nematic Transition and Molecular Weightsupporting

confidence: 88%

Simulations of nematic homopolymer melts using particle-based models with interactions expressed through collective variables

Daoulas

Rühle

Kremer

2012

J. Phys.: Condens. Matter

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We develop a hybrid Monte Carlo approach for modelling nematic liquid crystals of homopolymer melts. The polymer architecture is described with a discrete worm-like chain model. A quadratic density functional accounts for the limited compressibility of the liquid, while an additional quadratic functional of the local orientation tensor of the segments captures the nematic ordering. The approach can efficiently address large systems parametrized according to volumetric and conformational properties, representative of real polymeric materials. The results of the simulations regarding the influence of the molecular weight on the isotropic-nematic transition are compared to predictions from a Landau-de Gennes free energy expansion. The formation of the nematic phase is addressed within Rouse-like dynamics, realized using the current model.

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Section: The Isotropic-nematic Transition and Molecular Weightsupporting

confidence: 88%

Simulations of nematic homopolymer melts using particle-based models with interactions expressed through collective variables

Daoulas

Rühle

Kremer

2012

J. Phys.: Condens. Matter

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“…For semi-flexible rods with persistence length q ¼ k/kT, we expect the critical rod concentration threshold to decrease with increasing q. 2,71,72 For charged rods, Coulombic repulsion (bZ 2 ) will promote the isotropic phase and the critical rod concentration threshold increases with Z. 73 For thermotropic-lyotropic mixtures that undergo the IN transition but no phase demixing, DMS predicts that the mixture temperature threshold is a non-linear function of concentration and molecular weights; 74 the mixture IN transition can occur at a temperature lower than the transition temperature of the lower molecular weight component.…”

Section: Phase Ordering and Phase Separationmentioning

confidence: 99%

Liquid crystal models of biological materials and processes

2010

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This paper presents an overview of liquid crystal (LC) models of phase diagrams, phase transitions, self-assembly, interfaces, defects, and rheology and their integrated applications to biological mesophase materials and processes. Biological liquid crystals, classified into analogues (helicoidal plywoods), biopolymer solutions (in vitro DNA, polypeptides, collagen solutions) and in vivo LCs (membranes, silk, DNA), are discussed in terms of molecular characteristics and the symmetry of the thermodynamic phases. The thermodynamics and self-assembly of biological liquid crystals (BLCs) are discussed in terms of the Doi-Maier-Saupe lyotropic model and its extensions to chiral phases, showing the role of excluded volume and chirality. The defect physics of BLCs is described using the Landau-de Gennes model of chiral and achiral nematostatics to identify (i) thermodynamic phases, and (ii) observed textures and defect lattices under confinement and flow. The rheology and flow properties of BLCs are described using the Leslie-Ericksen and the Landau-de Gennes models of nematodynamics. The applications of integrated thermodynamic/defect/rheology modeling to the experimental characterization of several BLCs, including collagen and DNA solutions, are shown to provide organizing principles and quantitative tools to establish the properties of these natural materials. The phase transitions, tactoidal spherulites, flow-birefringence in dilute solutions, and banded textures in sheared concentrated solutions of collagen show how the principles of LC physics operate in BLC materials. Drying and spreading drops of DNA solutions leading to the formation of nematic monodomain aligned along the contact line are shown to follow self-assembly structuring under the action of interfacial, bulk, and contact line torques. Finally modeling of spider and silkworm LC spinning is presented as an example of biological polymer processing, where a high performance fiber material is produced through a lyotropic LC protein solution. The concerted structuring action of capillary confinement, strong anchoring, and nematic flow leads to predictions in agreement with the reported textural transitions in the duct of spiders and silkworms. The quantitative description of BLC materials and processes using mesoscopic models provides another tool to develop the science and future biomimetic applications of these ubiquitous natural anisotropic soft materials.

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“…Interactions between CNTs can be taken into account by extending the WLC free energy derived in this work by a director mean-field coupling of each CNT with the bulk of the material. Such an approach is often used in models of elastic liquid crystals and is known as the Maier–Saupe theory. , Such an approach would also allow one to consider CNT-CNT junction density and residual catalyst content in the coupling strength. Generally, on the one hand, we would expect an explicit inclusion of CNT-CNT interactions (other than within the considered CNT bundles) to further facilitate the alignment of CNTs due to favorable van der Waals attraction.…”

Section: Methodsmentioning

confidence: 99%

Highly Oriented Direct-Spun Carbon Nanotube Textiles Aligned by In Situ Radio-Frequency Fields

et al. 2022

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Carbon nanotubes (CNTs) individually exhibit exceptional physical properties, surpassing state-of-the-art bulk materials, but are used commercially primarily as additives rather than as a standalone macroscopic product. This limited use of bulk CNT materials results from the inability to harness the superb nanoscale properties of individual CNTs into macroscopic materials. CNT alignment within a textile has been proven as a critical contributor to narrow this gap. Here, we report the development of an altered direct CNT spinning method based on the floating catalyst chemical vapor deposition process, which directly interacts with the self-assembly of the CNT bundles in the gas phase. The setup is designed to apply an AC electric field to continuously align the CNTs in situ during the formation of CNT bundles and subsequent aerogel. A mesoscale CNT model developed to simulate the alignment process has shed light on the need to employ AC rather than DC fields based on a CNT stiffening effect (z-pinch) induced by a Lorentz force. The AC-aligned synthesis enables a means to control CNT bundle diameters, which broadened from 16 to 25 nm. The resulting bulk CNT textiles demonstrated an increase in the specific electrical and tensile properties (up to 90 and 460%, respectively) without modifying the quantity or quality of the CNTs, as verified by thermogravimetric analysis and Raman spectroscopy, respectively. The enhanced properties were correlated to the degree of CNT alignment within the textile as quantified by small-angle X-ray scattering and scanning electron microscopy image analysis. Clear alignment (orientational order parameter = 0.5) was achieved relative to the pristine material (orientational order parameter = 0.19) at applied field intensities in the range of 0.5–1 kV cm –1 at a frequency of 13.56 MHz.

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Effect of the flexibility on the phase transition of polymeric liquid crystals

Cited by 33 publications

References 10 publications

Simulations of nematic homopolymer melts using particle-based models with interactions expressed through collective variables

Simulations of nematic homopolymer melts using particle-based models with interactions expressed through collective variables

Liquid crystal models of biological materials and processes

Highly Oriented Direct-Spun Carbon Nanotube Textiles Aligned by In Situ Radio-Frequency Fields

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