Liquid Crystal Elastomers and Light

Palffy‐Muhoray, Peter

doi:10.1007/12_2011_165

Cited by 20 publications

(18 citation statements)

References 85 publications

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“…[11][12][13][14] If a CLC is polymerized into an elastomer (CLCE), a very interesting material arises, combining the striking optical properties of a cholesteric phase with the viscoelasticity of a rubber. [15,16] Because of the coupling between the cholesteric helix and the elastomeric network, a mechanical deformation changes the reflection color and often also the polarization. [17] A striking demonstration was the continuous and reversi ble tuning toward shorter wavelengths of a CLCE film with vertical helix by stretching biaxially in the film plane, equivalent to a uniaxial compression along the helix.…”

Section: Introductionmentioning

confidence: 99%

Facile Anisotropic Deswelling Method for Realizing Large‐Area Cholesteric Liquid Crystal Elastomers with Uniform Structural Color and Broad‐Range Mechanochromic Response

Kizhakidathazhath

Geng

Jampani

et al. 2019

Adv Funct Materials

105

125

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Cholesteric liquid crystal elastomers (CLCEs) are soft and dynamic photonic elements that couple the circularly polarized structural color from the cholesteric helix to the viscoelasticity of rubbers: the reflection color is mechanically tunable (mechanochromic response) over a broad range. This requires uniform helix orientation, previously realized by long‐term centrifugation to ensure anisotropic deswelling, or using sacrificial substrates or external fields. The present paper presents a simple, reproducible, and scalable method to fabricate highly elastic, large‐area, millimeters thick CLCE sheets with intense uniform reflection color that is repeatably, rapidly, and continuously tunable across the full visible spectrum by stretching or compressing. A precursor solution is poured onto a substrate and allowed to polymerize into a 3D network during solvent evaporation. Pinning to the substrate prevents in‐plane shrinkage, thereby realizing anisotropic deswelling in an unprecedentedly simple manner. Quantitative stress–strain–reflection wavelength characterization reveals behavior in line with theoretical predictions: two linear regimes are identified for strains below and above the helix unwinding threshold, respectively. Up to a doubling of the sample length, the continuous color variation across the full visible spectrum repeatedly follows a volume conserving function of the strain, allowing the CLCE to be used as optical high‐resolution strain sensor.

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Section: Introductionmentioning

confidence: 99%

Facile Anisotropic Deswelling Method for Realizing Large‐Area Cholesteric Liquid Crystal Elastomers with Uniform Structural Color and Broad‐Range Mechanochromic Response

Kizhakidathazhath

Geng

Jampani

et al. 2019

Adv Funct Materials

105

125

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“…[18][19][20][21] Since then, much effort has been made to improve the performance of photomobile polymer materials. [22][23][24][25][26][27][28][29][30][31][32] In this Minireview, we focus on CLCPs that macroscopically deform upon irradiation with actinic light. First, we introduce typical examples of photomobile polymer materials and their working mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Photomobile Polymer Materials with Crosslinked Liquid‐Crystalline Structures: Molecular Design, Fabrication, and Functions

2014

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Crosslinked liquid-crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction-expansion and bending-unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.

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“…f B is as in (17) and ǫ > 0 is a small positive parameter. We can obtain an explicit upper bound for the norm of a global energy minimizer using a maximum principle approach as shown below.…”

Section: Discussionmentioning

confidence: 99%

“…Let Q * be a global minimizer of F ǫ in the admissible space A in (14). Then |Q * | ≤ max 1 √ 6 , bǫ 2 √ 6(8 + 2ǫ 2 c) + 64 + 16ǫ 2 (c − 6a) + ǫ 4 (b 2 − 24ac) √ 6(8 + 2ǫ 2 c) , max r∈∂Ω |Q 0 | onΩ (87) where a, b, c are the bulk constants in f B in (17).…”

Section: Discussionmentioning

confidence: 99%

Equilibrium order parameters of nematic liquid crystals in the Landau-de Gennes theory

2010

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We study equilibrium liquid crystal configurations in three-dimensional domains, within the continuum Landau-De Gennes theory. We obtain explicit bounds for the equilibrium scalar order parameters in terms of the temperature and material-dependent constants. We explicitly quantify the temperature regimes where the Landau-De Gennes predictions match and the temperature regimes where the Landau-De Gennes predictions don't match the probabilistic second-moment definition of the Q-tensor order parameter. The regime of agreement may be interpreted as the regime of validity of the Landau-De Gennes theory since the Landau-De Gennes theory predicts large values of the equilibrium scalar order parameters -larger than unity, in the low-temperature regime. We discuss a modified Landau-De Gennes energy functional which yields physically realistic values of the equilibrium scalar order parameters in all temperature regimes.

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Liquid Crystal Elastomers and Light

Cited by 20 publications

References 85 publications

Facile Anisotropic Deswelling Method for Realizing Large‐Area Cholesteric Liquid Crystal Elastomers with Uniform Structural Color and Broad‐Range Mechanochromic Response

Facile Anisotropic Deswelling Method for Realizing Large‐Area Cholesteric Liquid Crystal Elastomers with Uniform Structural Color and Broad‐Range Mechanochromic Response

Photomobile Polymer Materials with Crosslinked Liquid‐Crystalline Structures: Molecular Design, Fabrication, and Functions

Equilibrium order parameters of nematic liquid crystals in the Landau-de Gennes theory

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