Domain structure and switching behavior of anisotropic gels

Hikmet, R. A. M.; Boots, H. M. J.

doi:10.1103/physreve.51.5824

Cited by 77 publications

(62 citation statements)

References 17 publications

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“…17 (b)). Similar behaviors have been observed in the case of dispersed silica particles on FLC matrix near the SmA-SmC phase transition [6][7][8]. However, Kundu et al [25] showed for other PSFLC systems that the soft-mode dielectric strength remains unchanged when the FLC cells are stabilized by a polymer network formed from a nonmesogenic reactive monomer.…”

Section: Polymer Network Morphology By Afm Investigationsmentioning

confidence: 66%

“…The polymer network is formed by chemical crosslinking of a small amount (few percent) of photo-reactive monomers dissolved in low molecular weight mesogenic material, through a polymerization reaction photochemically activated by a UV illumination. When the polymerization occurs in an aligned geometry, the resulting polymer network is roughly aligned parallel to the direction initially imposed by the liquid crystal medium in which the network has been formed [8]. Depending on the type of the reactive mesogen, the morphology of the polymer network may correspond to an open structure consisting of anisotropic fibrils [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…When the polymerization occurs in an aligned geometry, the resulting polymer network is roughly aligned parallel to the direction initially imposed by the liquid crystal medium in which the network has been formed [8]. Depending on the type of the reactive mesogen, the morphology of the polymer network may correspond to an open structure consisting of anisotropic fibrils [8][9][10]. The lateral size of fibrils is of the order of a few tenths of a micron [11][12][13]; their density increases with the initial reactive monomer concentration.…”

Section: Introductionmentioning

confidence: 99%

“…The polymer fibrils, by creating a large internal boundary, provide a bulk anchoring mechanism which allows a control of the liquid crystal alignment in the bulk. Application of an electric field causes a distortion of the liquid crystal host, which corresponds to a field-induced director rotation, without any reorientation of the fibrils [8] considered rigid by the authors because the network is heavily cross-linked. The structure of the polymer network has been observed using different techniques.…”

Section: Introductionmentioning

confidence: 99%

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Atomic Force Microscopy Observations of the Polymer Network Structure Formed in Ferroelectric Liquid Crystals Cells

Petit¹

2012

Polymerization

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Section: Polymer Network Morphology By Afm Investigationsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Atomic Force Microscopy Observations of the Polymer Network Structure Formed in Ferroelectric Liquid Crystals Cells

Petit¹

2012

Polymerization

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“…4 The model of the polymer matrix as a series of planes perpendicular to the x-, y-, and z-axes of the Cartesian coordinate system was introduced by Hikmet. 5 None of these models explicitly account for the observed dependence of the critical field on polymer concentration. In this paper we introduce a phenomenological model, which successfully describes the dependence of the critical field and the response time on the polymer concentration, and accounts for the change in the polymer network's characteristic length and anchoring strength as the polymer concentration is varied.…”

mentioning

confidence: 99%

Virtual surfaces, director domains, and the Fréedericksz transition in polymer-stabilized nematic liquid crystals

Kossyrev

Priezjev

et al. 2002

Applied Physics Letters

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The critical field of the Fréedericksz transition and switching dynamics are investigated for Polymer Stabilized Nematic Liquid Crystals as a function of polymer concentration.A simple phenomenological model is proposed to describe the observed critical field and dynamic response time behaviors as a function of concentration. In this model the polymer fibrils form director domains, which are bounded by "virtual surfaces" with a finite anchoring energy. The Fréedericksz transition occurs independently within each of these domains.

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Polymer-Filled Nematics: A New Class of Light-Scattering Materials for Electro-Optical Switches

et al. 2000

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The nearly constant value of the Raman peak corroborates our assumption about the tube sliding within the bundle. The paper by Salvetat et al., [12] in which SWNT bundles are loaded with an AFM, also supports this hypothesis. As the tube bundles grow in diameter, both the axial modulus and shear modulus decrease dramatically, suggesting that individual SWNTs are slipping within the bundle and decreasing the load required to deform the bundle. [12] We stress that it is the low-modulus features of the bundles, and not the axial modulus of individual tubes, that control the mechanical stability and strength of the SWNT±polymer composite. Our experiments show strong evidence to this effect. When nanotube applications as reinforcements are considered, it is important to consider the most effective ways of obtaining strengthening: for example, by breaking bundles into individual tube fragments (say, fullerene pipes [14] ) and dispersing these segments in the matrix. On the other hand, strengthening could also come from reinforcing the bundles themselves by crosslinking the tubes within bundles (e.g., via irradiation or chemical treatments) to increase the bundle rigidity and eliminate tube slippage. Even if this is achieved, one will have to worry about a strong tube±polymer interface. The formation of strong interfaces in carbon nanotube±polymer composites could be challenging but could be done through functionalization of the tube fragment ends and tube body, which then can be chemically bonded to the polymer chains.Nanotube reinforcements, however, will increase the toughness of the composites by absorbing energy because of their highly flexible elastic behavior during loading. Other interesting applications could be in creating nanotube-filled adhesive polymer films where adhesion between nanotube-filled polymer surfaces could be greatly enhanced by some kind of reversible Velcro effect at the nanoscale, due to the attractive van der Waals forces between the nanotubes present on each of the surfaces, as was observed in Figure 1a. As we stated earlier in our work on MWNTs, the low density of the nanotubes will clearly be an advantage for composites. Nanotubes would also offer multifunctionality; for example, conducting polymer structures may be constructed at low loadings of nanotube fillers due to lower percolation thresholds needed for the high aspect ratio nanotube structures. Nature 1999, 399, 761. [11] The shear modulus of an isolated SWNT is much larger and can be related to the elastic constants of graphite as 0.5 (C 11 ±C 12 ) = 440 GPa. This is not the magnitude relevant for the present experimental studies. In the case of the nanotube rope, its shear modulus is related to that of graphite by the ratio of the distance between tube±tube layers divided by the graphitic interplanar distance. This comes out as approximately, G rope~5 G graphite (see [12] for details of this relationship), suggesting that for a nanotube rope (assuming disorder) the lower limit for G will be~1 GPa.[12] J. , Phys. Rev. Lett. 19...

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Domain structure and switching behavior of anisotropic gels

Cited by 77 publications

References 17 publications

Atomic Force Microscopy Observations of the Polymer Network Structure Formed in Ferroelectric Liquid Crystals Cells

Atomic Force Microscopy Observations of the Polymer Network Structure Formed in Ferroelectric Liquid Crystals Cells

Virtual surfaces, director domains, and the Fréedericksz transition in polymer-stabilized nematic liquid crystals

Polymer-Filled Nematics: A New Class of Light-Scattering Materials for Electro-Optical Switches

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