X-ray diffraction by liquid-crystalline elastomers

Degert, C.; Megtert, S.; Petermann, D.; Mauzac, M.

doi:10.1080/02678299208029122

Cited by 20 publications

(11 citation statements)

References 14 publications

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“…The smectic A structure was established by twodimensional X-ray measurements taken on samples orientated by mechanical stretching. 15 Gels can be overswollen with respect to the preparation conditions. Samples prepared in d-toluene were put in a large excess of d-toluene and swollen to saturation in order to reach their maximum swelling ratio (Table 1).…”

Section: Methodsmentioning

confidence: 99%

SANS Experiments on Swollen Mesomorphous Networks

Zanna

Mauzac

1999

Macromolecules

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The structure of mesomorphous elastomers, made of cross-linked side-chain liquid crystal polymers, is investigated by small-angle neutron scattering. Three types of samples are synthesized in the presence of deuterated toluene, one without mesogenic groups (C) and two with different proportions of pending mesogenic side chains (A and B). SANS is measured at the preparation concentration state and at maximum swelling, in equilibrium with deuterated solvent. These experiments give a test of the homogeneity of cross-linking. Samples carrying bulky mesogenic side groups (A and B) appear to be less heterogeneous than the corresponding mesogen-free network (C). Results are discussed in terms of mesomorphous interactions which are still present at the preparation swelling ratio and in terms of a steric effect due to the side chains, which prevents chains from interpenetrating and entangling.

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Section: Methodsmentioning

confidence: 99%

SANS Experiments on Swollen Mesomorphous Networks

Zanna

Mauzac

1999

Macromolecules

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“…It has been realized since the early studies that in this way one can manipulate the LC order of the LCE. [29][30][31][32] A fundamental mechanism here is that an applied stress induces an anisotropy in the polymer backbone, which results in a macroscopic alignment of the director by virtue of coupling. 16 Due to this, the load induces remarkable changes in the structure of the LCE, if its axis is not collinear with the axis of initial anisotropy of backbones.…”

Section: Introductionmentioning

confidence: 99%

Modelling elasticity and memory effects in liquid crystalline elastomers by molecular dynamics simulations

et al. 2012

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We performed molecular dynamics simulations of a liquid crystal elastomer of side-chain architecture. The network is formed from a melt of 28 molecules each having a backbone of 100 hydrocarbon monomers, to which 50 side chains are attached in a syndiotactic way. Crosslinking is performed in the smectic A phase. We observe an increase of the smectic-isotropic phase transition temperature of about 5 degrees as compared to the uncrosslinked melt. Memory effects in liquid crystalline order and in sample shape are well reproduced when the elastomer is driven through the smectic-isotropic transition. Above this transition, in the isotropic phase, the polydomain smectic phase is induced by a uniaxial load. Below the transition, in a monodomain smectic A phase, both experimentally observed effects of homogeneous director reorientation and stripe formation are reproduced when the sample is stretched along the director. When the load is applied perpendicularly to the director, the sample demonstrates reversible deformation with no change of liquid crystalline order, indicating elasticity of the two-dimensional network of polymer layers.

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“…The polymer conformation and chain anisotropy of liquid-crystalline elastomers were also the object of several studies, based on a combination of X-ray techniques (namely SAXS and WAXS) [75,76] and small-angle neutron scattering (SANS) [77,78,79]. However, to our knowledge, no such studies were performed to investigate the ordering and structural properties of nanomaterial/LCE composites.…”

Section: Lce-based Composites With Other Nanomaterialsmentioning

confidence: 99%

Nanostructured Composites Based on Liquid-Crystalline Elastomers

et al. 2018

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Liquid-crystalline elastomers (LCEs) are the object of many research investigations due to their reversible and controllable shape deformations, and their high potential for use in the field of soft robots and artificial muscles. This review focuses on recent studies about polymer composites based on LCEs and nanomaterials having different chemistry and morphology, with the aim of instilling new physical properties into LCEs. The synthesis, physico-chemical characterization, actuation properties, and applications of LCE-based composites reported in the literature are reviewed. Several cases are discussed: (1) the addition of various carbon nanomaterials to LCEs, from carbon black to carbon nanotubes, to the recent attempts to include graphene layers to enhance the thermo-mechanic properties of LCEs; (2) the use of various types of nanoparticles, such as ferroelectric ceramics, gold nanoparticles, conductive molybdenum-oxide nanowires, and magnetic iron-oxide nanoparticles, to induce electro-actuation, magnetic-actuation, or photo-actuation into the LCE-based composites; (3) the deposition on LCE surfaces of thin layers of conductive materials (i.e., conductive polymers and gold nanolayers) to produce bending actuation by applying on/off voltage cycles or surface-wrinkling phenomena in view of tunable optical applications. Some future perspectives of this field of soft materials conclude the review.

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X-ray diffraction by liquid-crystalline elastomers

Cited by 20 publications

References 14 publications

SANS Experiments on Swollen Mesomorphous Networks

SANS Experiments on Swollen Mesomorphous Networks

Modelling elasticity and memory effects in liquid crystalline elastomers by molecular dynamics simulations

Nanostructured Composites Based on Liquid-Crystalline Elastomers

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