Liquid crystal elastomers, networks and gels: advanced smart materials

Xie, Ping; Zhang, Rongben

doi:10.1039/b413835j

Cited by 185 publications

(139 citation statements)

References 111 publications

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“…The crystal structure will provide a strong scattering when the direction of the crystal planes forms an angle to the x-ray beam and satisfies the Bragg equation [7], 2 sin dn   , (1) where d : distance between crystal planes,  : angle of deviation, n : orde (integer number: 0, 1, 2, 3, ...), and  : wavelength. For polymeric materials, the x-ray diffraction method provide information about the structure of the polymer shown by the crystalline and amorphous state mixing randomly.…”

Section: Methodsmentioning

confidence: 99%

“…Liquid Crystal Elastomers (LCEs), both MCLCEs and SCLCEs (Side Chain Liquid Crystal Elastomers) are polymers produced by crosslinking of liquid crystal polymers covalently with monomers are mesogen units forming a three dimension network [1,2,3]. Mechanical properties of the LCEs can be controlled by selection of liquid crystal phase, density of crosslinkers, their flexible polymer backbones, merger of the backbones, the group of liquid crystals and external stimuli [1,2,4].…”

Section: Introductionmentioning

confidence: 99%

“…Mechanical properties of the LCEs can be controlled by selection of liquid crystal phase, density of crosslinkers, their flexible polymer backbones, merger of the backbones, the group of liquid crystals and external stimuli [1,2,4]. The MCLCE materials were synthesized by the reaction of vinyl-or vinoloxy-end mesogens under condition hydrosilylation with crosslinker agent was pentamethylcyclopentasiloxane (C 5 H 20 O 5 Si 2 ) and the mesogen unit was monomer 2-ethyl-1,4-phenylen bis [4 -[4 -(viniloxy) [4,5].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Main-Chain Liquid Crystal Elastomers Using X-ray Diffraction Method

Supardi

Yusuf

Harsoyo³

2014

Proceedings of the 2014 International Conference on Physics

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Abstract-We characterized the four main chain liquid crystal elastomers (MCLCEs) samples using the x-ray diffraction method. The four samples had different concentration of crosslinkers, i.e 8%, 12%, 14% and 16%. There was a relationship between crosslinkers concentration and d-spacing parameter here, namely when the concentration increased the d-spacing parameter did, too. In polymeric material, the dspacing parameter indicates the average of length between dominant clusters of the heavy molecule. We also calculated the degree of crystallinity and amorphousinity based on the difractogram obtained from the characterization and associated them to their mechanical properties. We found that as the degree of crystallinity decreased (or degree of amorphousinity increased) the sample will be more elastic, and vice versa.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Main-Chain Liquid Crystal Elastomers Using X-ray Diffraction Method

Supardi

Yusuf

Harsoyo³

2014

Proceedings of the 2014 International Conference on Physics

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“…It is known that liquid-crystalline elastomers (LCEs) exhibit a spontaneous contraction along the director axis when heated above their nematic (N)-isotropic (I) phase-transition temperatures. [15][16][17] On the other hand, when azobenzene chromophores are incorporated into LCEs, they can undergo the contraction isothermally because of the change in alignment order by light. [18][19][20] Furthermore, as the extinction coefficient of the azobenzene moieties at approximately 360 nm is large (about 2.0 10 4 L mol À1 cm À1 ) and more than 99 % of the incident photons are absorbed by the surface with a thickness of less than 1 mm, LCE films with a high concentration of azobenzene moieties can generate an alignment change only in the film surface upon exposure to actinic UV light.…”

mentioning

confidence: 99%

How Does the Initial Alignment of Mesogens Affect the Photoinduced Bending Behavior of Liquid‐Crystalline Elastomers?

2006

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“…Nematic elastomers (NEs) are a unique class of materials (19)(20)(21)(22)(23). Formed by cross-linking liquid crystalline polymers, NEs possess both the elastic properties of rubbers and the orientational properties of liquid crystals.…”

mentioning

confidence: 99%

Shape selection of twist-nematic-elastomer ribbons

Sawa

Urayama

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

239

216

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How microscopic chirality is reflected in macroscopic scale to form various chiral shapes, such as straight helicoids and spiral ribbons, and how the degree of macroscopic chirality can be controlled are a focus of studies on the shape formation of many biomaterials and supramolecular systems. This article investigates both experimentally and theoretically how the chiral arrangement of liquid crystal mesogens in twist-nematic-elastomer films induces the formation of helicoids and spiral ribbons because of the coupling between the liquid crystalline order and the elasticity. It is also shown that the pitch of the formed ribbons can be tuned by temperature variation. The results of this study will facilitate the understanding of physics for the shape formation of chiral materials and the designing of new structures on basis of microscopic chirality.liquid crystal elastomers | chiral imprinting R ecent researches have revealed that chirality plays a critical role in controlling the shape of self-assembled supramolecular aggregates. A range of chiral shapes, including tubes with "barber-pole" markings, spiral ribbons (with cylindrical curvature and helical central line), and helicoids (with Gaussian saddle-like curvature and straight central line), have been observed in a rich variety of biological materials and their synthetic analogues. These materials include several amphiphiles (1-3), peptides (4-7), diacetylenic lipids (8, 9), gemini surfactants (10, 11), and multicomponent mixtures in bile (12, 13). Such aggregates often become bilayers, and the bilayer membranes form tubules, spiral ribbons, or helicoids in contrast to the normal expectation that the minimum energy state of the bilayers would be flat, or be large spherical vesicles with the minimum curvature. In addition, the correlation between material characteristics and the macroscopic shape of chiral aggregates is markedly complicated. For example, mixed bilayers of saturated and diacetylenic phospholipids change their shape between micron-scale cylindrical tubules, spiral ribbons, or nanometer-scale tubules, in response to temperature variation (14). Charged gemini surfactants with chiral counterions show a transition between spiral ribbons and helicoids as a function of molecular chain length (10). Many theoretical studies have been reported to explain what determines the size and shape of tubules, helicoids, and spiral ribbons (10,(15)(16)(17)(18).In this article, we will show, both experimentally and theoretically, how a flat twist-nematic-elastomer (TNE) film when subjected to temperature change can easily achieve the goal of shape selection between helicoids and spiral ribbons. Nematic elastomers (NEs) are a unique class of materials (19-23). Formed by cross-linking liquid crystalline polymers, NEs possess both the elastic properties of rubbers and the orientational properties of liquid crystals. The combination of these two properties makes the shape of NEs very sensitive to external stimuli. In this article, we will focus on NE films in which the...

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Liquid crystal elastomers, networks and gels: advanced smart materials

Cited by 185 publications

References 111 publications

Characterization of Main-Chain Liquid Crystal Elastomers Using X-ray Diffraction Method

Characterization of Main-Chain Liquid Crystal Elastomers Using X-ray Diffraction Method

How Does the Initial Alignment of Mesogens Affect the Photoinduced Bending Behavior of Liquid‐Crystalline Elastomers?

Shape selection of twist-nematic-elastomer ribbons

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