Flow perturbation model for filament buckling

Rey, Alejandro D.; Abukhdeir, Nasser Mohieddin

doi:10.1016/j.jnnfm.2008.01.005

Cited by 5 publications

(9 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These results agree with past work in nematic systems where an increase in temperature increases the separation distance between the disclination defects [31]. In addition to defects in the underlying orientational order, the model predicts the formation of translational defects, elementary dislocations, enclosing the misoriented core The second general cylindrical domain structure (9a and 10a) shows a fully melted/disordered core structure that has been predicted in the past for smectic-A filaments [48]. In this shallow undercooling scenario, the free energy difference between the smectic and isotropic phases is less than that of the formation of defects, as in the cases of 9a-b.…”

Section: Nano-scale Structuresupporting

confidence: 89%

“…The smectic-A mesophase, with its lamellar ordering on the molecular scale, exhibits growth, defect, and texture phenomena not seen in the nematic phases, including the lamellar-like cholesteric mesophase. In addition to spheroids and sphero-cylinders observed in nematics, direct isotropic/smectic-A liquid crystals exhibit the fascinating highly anisotropic “batonnet” structures of Friedel and Grandjean − and complex buckling filaments. − As there are many factors involved, a discussion of the phase transformation processes in these materials will be presented before analyzing the experimental results in detail, in order to guide the interpretation of the observed morphologies.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition

2009

Self Cite

View full text Add to dashboard Cite

Experimental and modeling/simulation studies of phase equilibrium and growth morphologies of novel polymer-dispersed liquid crystal (PDLC) mixtures of PS (polystyrene) and liquid crystals that exhibit a direct isotropic/smectic-A (lamellar) mesophase transition were performed for PS/10CB (decylcyanobiphenyl) and PS/12CB (dodecyl-cyanobiphenyl). Partial phase diagrams were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) for different compositions of both materials, determining both phase separation (liquid/liquid demixing) and phase ordering (isotropic/smectic-A transition) temperatures. The Flory-Huggins theory of isotropic mixing and Maier-Saupe-McMillan theory for smectic-A liquid crystalline ordering were used to computationally determine phase diagrams for both systems, showing good agreement with the experimental results. In addition to thermodynamic observations, growth morphology relations were found depending on phase transition sequence, quench rate, and material composition. Three stages of liquid crystal-rich domain growth morphology were observed: spherical macroscale domain growth ("stage I"), highly anisotropic domain growth ("stage II"), and sub-micron spheroid domain growth ("stage III"). Nano-scale structure of spheroidal and spherocylindrical morphologies were then determined via two-dimensional simulation of a high-order Landau-de Gennes model. Morphologies observed during stage II growth are typical of direct isotropic/smectic-A phase transitions, such as highly anisotropic "batonnets" and filaments. These morphologies, which are found to be persistent in direct isotropic/smectic-A PDLCs, could provide new functionality and applications for these functional materials.

show abstract

Section: Nano-scale Structuresupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition

2009

Self Cite

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

“…The current work studies an alternate initial configuration where the nucleus is homogeneously, or "ideally," oriented. This and past work (10)(11)(12)14) focuses on rod-like low molecular mass liquid crystals and phenomenological parameters are based, in part, on experimental data from 12CB (dodecyl-cyanobiphenyl). This work neglects nucleation mechanisms, thermal fluctuations, heat of transition, impurities, and convective flow while taking into account energetically the intercoupling between orientational/translational order and variation of smectic layer spacing.…”

Section: Introductionmentioning

confidence: 99%

“…Following this, numerical simulation was used to study phase transition kinetics and defect dynamics (10), surface effects (11), and most recently spherulite growth (12). In addition to these simulation studies, theoretical contributions have been made to the study of smectic-A filamentary growth and buckling (13,14).Past work on smectic-A spherulite growth has focused on initially radially oriented nuclei (12). The current work studies an alternate initial configuration where the nucleus is homogeneously, or "ideally," oriented.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

Abukhdeir

Rey

2009

Liquid Crystals

Self Cite

View full text Add to dashboard Cite

A Landau-de Gennes model that integrates the nematic quadrupolar tensor order parameter and complex smectic-A order parameters is used to simulate the two-dimensional growth of an initially homogeneous smectic-A spherulite in an isotropic matrix. These simulations are performed in the shape-dynamic (nano-scale) regime of growth under two material conditions: isotropic nematic elasticity and equal splay-bend nematic elasticity. A comparison of the growth kinetics, spherulite morphology, interfacial/bulk energy landscapes between both cases is made showing that equal nematic splay-bend elasticity is required to reproduce past experimental and theoretical observations. Additionally, a previously unknown undulation instability during spherulite growth is found which, in conjunction with preferred planar anchoring and defect shedding mechanisms at micron length scales, could explain the formation mechanism of focal conic curvature defects and ultimately smectic-A "batonnet" structures observed experimentally. of this mesophase via modelling and simulation. The key role that this mesophase plays in biological systems alone shows the importance of this single contribution of de Gennes. In his Nobel lecture in 1991, he states that "smectics bring me naturally to another important feature of complex fluids -namely that, in our days, it is sometimes possible to create new forms of matter" which alludes to the types of applications of smectics that could be developed in the future and to their roles in biological systems.The most simple of the smectics is the smectic-A mesophase, which displays lamellar translational ordering, in addition to the orientational ordering of nematics. Recently an increasing amount of interest in this mesophase, in particular of materials exhibiting a direct isotropic/smectic-A (disordered/ordered) transition, has resulted in many experimental and theoretical results. Nonetheless, the understanding of this mesophase is in a nascent stage. Much of this is due to the time and length scales at which the structures and dynamics occur being on the nanoscale. These properties provide a obvious application of theoretical study through modelling and simulation in order to both enhance experimental research and make predictions independently.A fascinating range of liquid crystal growth morphologies have been the focus on much study (6). The smectic-A mesophase, with its lamellar ordering on the molecular scale, exhibits growth, defect, and texture phenomena not seen in the nematic phases, including the lamellar-like cholesteric mesophase. Focusing on the growth phenomena solely, on transition from the isotropic/disordered phase, a variety of self-assembled smectic-A structures have been observed to form. These unique morphologies can be attributed to complex dynamics involving interfacial tension anisotropy, which results in preferred anchoring, and bulk texturing.The current study is a part of an overall effort to understand kinetics, dynamics, and morphology of the direct isotropic/smectic-A liquid cry...

show abstract

Generalized Boussinesq-Scriven surface fluid model with curvature dissipation for liquid surfaces and membranes

Gutierrez

Herrera‐Valencia²,

Rey

2017

Journal of Colloid and Interface Science

View full text Add to dashboard Cite

Flow perturbation model for filament buckling

Cited by 5 publications

References 18 publications

Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition

Thermodynamics, Transition Dynamics, and Texturing in Polymer-Dispersed Liquid Crystals with Mesogens Exhibiting a Direct Isotropic/Smectic-A Transition

Shape-dynamic growth, structure, and elasticity of homogeneously oriented spherulites in an isotropic/smectic-A mesophase transition

Generalized Boussinesq-Scriven surface fluid model with curvature dissipation for liquid surfaces and membranes

Contact Info

Product

Resources

About