High strain actuation liquid crystal elastomers via modulation of mesophase structure

Soft Matter ◽  
2017 ◽  
Vol 13 (41) ◽  
pp. 7537-7547 ◽  
Author(s):  
Mohand O. Saed ◽  
Ross H. Volpe ◽  
Nicholas A. Traugutt ◽  
Rayshan Visvanathan ◽  
Noel A. Clark ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
High Strain ◽  
Stimuli Responsive ◽  
Critical Aspect ◽  
Liquid Crystal Elastomers

Control of the mesophase in liquid crystalline elastomers (LCEs) is a critical aspect in harnessing their unique stimuli-responsive properties.

scholarly journals Effect of Crosslinkers on Optical and Mechanical Behavior of Chiral Nematic Liquid Crystal Elastomers

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6193
Author(s):  
Kyosun Ku ◽  
Kyohei Hisano ◽  
Kyoko Yuasa ◽  
Tomoki Shigeyama ◽  
Norihisa Akamatsu ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Molar Ratio ◽  
Stimuli Responsive ◽  
Breaking Strain ◽  
Responsive Materials ◽  
Sensor Applications ◽  
Color Changes ◽  
Chiral Nematic ◽  
Liquid Crystal Elastomers

Chiral nematic (N*) liquid crystal elastomers (LCEs) are suitable for fabricating stimuli-responsive materials. As crosslinkers considerably affect the N*LCE network, we investigated the effects of crosslinking units on the physical properties of N*LCEs. The N*LCEs were synthesized with different types of crosslinkers, and the relationship between the N*LC polymeric system and the crosslinking unit was investigated. The N*LCEs emit color by selective reflection, in which the color changes in response to mechanical deformation. The LC-type crosslinker decreases the helical twisting power of the N*LCE by increasing the total molar ratio of the mesogenic compound. The N*LCE exhibits mechano-responsive color changes by coupling the N*LC orientation and the polymer network, where the N*LCEs exhibit different degrees of pitch variation depending on the crosslinker. Moreover, the LC-type crosslinker increases the Young’s modulus of N*LCEs, and the long methylene chains increase the breaking strain. An analysis of experimental results verified the effect of the crosslinkers, providing a design rationale for N*LCE materials in mechano-optical sensor applications.

Artificial muscles based on liquid crystal elastomers

2006 ◽  
Vol 364 (1847) ◽  
pp. 2763-2777 ◽  
Author(s):  
Min-Hui Li ◽  
Patrick Keller
Keyword(s):  
Liquid Crystal ◽  
Main Chain ◽  
Uv Light ◽  
Shape Change ◽  
Artificial Muscle ◽  
Isotropic Phase ◽  
Artificial Muscles ◽  
Stimuli Responsive ◽  
Liquid Crystal Elastomers ◽  
The Individual

This paper presents our results on liquid crystal (LC) elastomers as artificial muscle, based on the ideas proposed by de Gennes. In the theoretical model, the material consists of a repeated series of main-chain nematic LC polymer blocks, N, and conventional rubber blocks, R, based on the lamellar phase of a triblock copolymer RNR. The motor for the contraction is the reversible macromolecular shape change of the chain, from stretched to spherical, that occurs at the nematic-to-isotropic phase transition in the main-chain nematic LC polymers. We first developed a new kind of muscle-like material based on a network of side-on nematic LC homopolymers. Side-on LC polymers were used instead of main-chain LC polymers for synthetic reasons. The first example of these materials was thermo-responsive, with a typical contraction of around 35–45% and a generated force of around 210 kPa. Subsequently, a photo-responsive material was developed, with a fast photochemically induced contraction of around 20%, triggered by UV light. We then succeeded in preparing a thermo-responsive artificial muscle, RNR, with lamellar structure, using a side-on nematic LC polymer as N block. Micrometre-sized artificial muscles were also prepared. This paper illustrates the bottom-up design of stimuli-responsive materials, in which the overall material response reflects the individual macromolecular response, using LC polymer as building block.

scholarly journals Nematic liquid crystalline elastomers are aeolotropic materials

2021 ◽  
Vol 477 (2253) ◽  
pp. 20210259
Author(s):  
L. Angela Mihai ◽  
Haoran Wang ◽  
Johann Guilleminot ◽  
Alain Goriely
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Additional Term ◽  
Elastic Response ◽  
Order Effects ◽  
Nematic Order ◽  
Nematic Elastomers ◽  
Strain Limit ◽  
Liquid Crystal Elastomers ◽  
Dynamics Simulations

Continuum models describing ideal nematic solids are widely used in theoretical studies of liquid crystal elastomers. However, experiments on nematic elastomers show a type of anisotropic response that is not predicted by the ideal models. Therefore, their description requires an additional term coupling elastic and nematic responses, to account for aeolotropic effects. In order to better understand the observed elastic response of liquid crystal elastomers, we analyse theoretically and computationally different stretch and shear deformations. We then compare the elastic moduli in the infinitesimal elastic strain limit obtained from the molecular dynamics simulations with the ones derived theoretically, and show that they are better explained by including nematic order effects within the continuum framework.

scholarly journals Liquid Crystal Elastomers for Biological Applications

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 813
Author(s):  
Mariam Hussain ◽  
Ethan I. L. Jull ◽  
Richard J. Mandle ◽  
Thomas Raistrick ◽  
Peter J. Hine ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Stimuli Responsive ◽  
Absorption Properties ◽  
Liquid Crystal Elastomer ◽  
Cell Scaffolds ◽  
Artificial Tissue ◽  
Recent Developments ◽  
Liquid Crystal Elastomers ◽  
Potential Use

The term liquid crystal elastomer (LCE) describes a class of materials that combine the elastic entropy behaviour associated with conventional elastomers with the stimuli responsive properties of anisotropic liquid crystals. LCEs consequently exhibit attributes of both elastomers and liquid crystals, but additionally have unique properties not found in either. Recent developments in LCE synthesis, as well as the understanding of the behaviour of liquid crystal elastomers—namely their mechanical, optical and responsive properties—is of significant relevance to biology and biomedicine. LCEs are abundant in nature, highlighting the potential use of LCEs in biomimetics. Their exceptional tensile properties and biocompatibility have led to research exploring their applications in artificial tissue, biological sensors and cell scaffolds by exploiting their actuation and shock absorption properties. There has also been significant recent interest in using LCEs as a model for morphogenesis. This review provides an overview of some aspects of LCEs which are of relevance in different branches of biology and biomedicine, as well as discussing how recent LCE advances could impact future applications.

scholarly journals Electrocaloric and elastocaloric effects in soft materials

2016 ◽  
Vol 374 (2074) ◽  
pp. 20150301 ◽  
Author(s):  
Maja Trček ◽  
Marta Lavrič ◽  
George Cordoyiannis ◽  
Boštjan Zalar ◽  
Brigita Rožič ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Main Chain ◽  
Soft Materials ◽  
Ion Density ◽  
Caloric Effect ◽  
Direct Measurements ◽  
Cooling Devices ◽  
Composite Mixture ◽  
Liquid Crystal Elastomers

Materials with large caloric effect have the promise of realizing solid-state refrigeration which has potential to be more efficient and environmentally friendly compared with current cooling technologies. Recently, the focus of caloric effects investigations has shifted towards soft materials. An overview of recent direct measurements of the large electrocaloric effect (ECE) in a composite mixture of a liquid crystal and nanoparticles (NPs) and large elastocaloric (eC) effect in main-chain liquid crystal elastomers is given. In mixtures of 12CB liquid crystal with functionalized CdSSe NPs, an ECE exceeding 5 K was found in the vicinity of the isotropic to smectic A phase transition. It is shown that the NPs smear the isotropic to smectic coexistence range in which a large ECE is observed due to latent heat enhancement. NPs acting as traps for ions reduce the moving-ion density and consequently the Joule heating. Direct eC measurements indicate that the significant eC response can be found in main-chain liquid crystalline elastomers, but at a fraction of the stress field in contrast to other eC materials. Both soft materials could play a significant role as active cooling elements or parts of thermal diodes in development of new cooling devices. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

Stimuli-responsive liquid crystal elastomers for dynamic cell culture

2015 ◽  
Vol 30 (4) ◽  
pp. 453-462 ◽  
Author(s):  
Aditya Agrawal ◽  
Oluwatomiyin Adetiba ◽  
Hojin Kim ◽  
Huiying Chen ◽  
Jeffrey G. Jacot ◽  
...  
Keyword(s):  
Cell Culture ◽  
Liquid Crystal ◽  
Stimuli Responsive ◽  
Dynamic Cell ◽  
Liquid Crystal Elastomers ◽  
Image Position

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