Main-chain liquid-crystal elastomers versus side-chain liquid-crystal elastomers: similarities and differences in their mechanical properties

Soft Matter ◽  
2018 ◽  
Vol 14 (31) ◽  
pp. 6449-6462 ◽  
Author(s):  
D. Rogez ◽  
S. Krause ◽  
P. Martinoty
Keyword(s):  
Mechanical Properties ◽  
Liquid Crystal ◽  
Main Chain ◽  
Poisson Ratio ◽  
Side Chain ◽  
Similarities And Differences ◽  
Liquid Crystal Elastomers

The shear and Young moduli, the poly-domain to mono-domain transition, the Poisson ratio and the supercritical or subcritical nature of main-chain and side-chain liquid-crystal elastomers are characterized with various mechanical experiments.

scholarly journals Effect of Isomeric Amine Chain Extenders and Crosslink Density on the Properties of Liquid Crystal Elastomers

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3094
Author(s):  
Yoojin Lee ◽  
Subi Choi ◽  
Beom-Goo Kang ◽  
Suk-kyun Ahn
Keyword(s):  
Mechanical Properties ◽  
Liquid Crystal ◽  
Molecular Engineering ◽  
Side Chain ◽  
Aerospace Medicine ◽  
Different Types ◽  
Chain Extenders ◽  
Liquid Crystal Elastomers ◽  
Soft Actuators ◽  
Significant Attention

Among the various types of shape changing materials, liquid crystal elastomers (LCEs) have received significant attention as they can undergo programmed and reversible shape transformations. The molecular engineering of LCEs is the key to manipulating their phase transition, mechanical properties, and actuation performance. In this work, LCEs containing three different types of butyl groups (n-, iso-, and sec-butyl) in the side chain were synthesized, and the effect of isomeric amine chain extenders on the thermal, mechanical, and actuation properties of the resulting LCEs was investigated. Because of the considerably low reactivity of the sec-butyl group toward the diacrylate in the LC monomer, only a densely crosslinked LCE was synthesized. Most interestingly, the mechanical properties, actuation temperature, and blocking stress of the LCEs comprising isobutyl groups were higher than those of the LCEs comprising n-butyl groups. This difference was attributed to the presence of branches in the LCEs with isobutyl groups, which resulted in a tighter molecular packing and reduced the free volume. Our results suggest a facile and effective method for synthesizing LCEs with tailored mechanical and actuation properties by the choice of chain extenders, which may advance the development of soft actuators for a variety of applications in aerospace, medicine, and optics.

scholarly journals Internal constraints and arrested relaxation in main-chain nematic elastomers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Takuya Ohzono ◽  
Kaoru Katoh ◽  
Hiroyuki Minamikawa ◽  
Mohand O. Saed ◽  
Eugene M. Terentjev
Keyword(s):  
Mechanical Properties ◽  
Main Chain ◽  
Polymer Networks ◽  
Nematic Order ◽  
Nematic Elastomers ◽  
Nematic Director ◽  
Highly Nonlinear ◽  
Nonlinear Mechanical ◽  
Liquid Crystal Elastomers ◽  
Memory Applications

AbstractNematic liquid crystal elastomers (N-LCE) exhibit intriguing mechanical properties, such as reversible actuation and soft elasticity, which manifests as a wide plateau of low nearly-constant stress upon stretching. N-LCE also have a characteristically slow stress relaxation, which sometimes prevents their shape recovery. To understand how the inherent nematic order retards and arrests the equilibration, here we examine hysteretic stress-strain characteristics in a series of specifically designed main-chain N-LCE, investigating both macroscopic mechanical properties and the microscopic nematic director distribution under applied strains. The hysteretic features are attributed to the dynamics of thermodynamically unfavoured hairpins, the sharp folds on anisotropic polymer strands, the creation and transition of which are restricted by the nematic order. These findings provide a new avenue for tuning the hysteretic nature of N-LCE at both macro- and microscopic levels via different designs of polymer networks, toward materials with highly nonlinear mechanical properties and shape-memory applications.

Microscopy of Diffuse Nematic–Isotropic Transition in Main-Chain Nematic Liquid-Crystal Elastomers

2021 ◽  
Vol 54 (8) ◽  
pp. 3678-3688
Author(s):  
Takuya Ohzono ◽  
Kaoru Katoh ◽  
Eugene M. Terentjev
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Main Chain ◽  
Liquid Crystal Elastomers

Effect of stretching angle on the stress plateau behavior of main-chain liquid crystal elastomers

Soft Matter ◽  
2021 ◽  
Vol 17 (11) ◽  
pp. 3128-3136
Author(s):  
Suzuka Okamoto ◽  
Shinichi Sakurai ◽  
Kenji Urayama
Keyword(s):  
Liquid Crystal ◽  
Main Chain ◽  
Stress Plateau ◽  
Liquid Crystal Elastomer ◽  
Ultimate Elongation ◽  
Liquid Crystal Elastomers

Stretching angle for a main-chain liquid crystal elastomer has pronounced effects on the width of the stress plateau as well as the ultimate elongation, while it has no effect on the plateau height.

Thermomechanical properties of monodomain nematic main-chain liquid crystal elastomers

Soft Matter ◽  
2018 ◽  
Vol 14 (29) ◽  
pp. 6024-6036 ◽  
Author(s):  
Daniel R. Merkel ◽  
Nicholas A. Traugutt ◽  
Rayshan Visvanathan ◽  
Christopher M. Yakacki ◽  
Carl P. Frick
Keyword(s):  
Liquid Crystal ◽  
Main Chain ◽  
Reaction Scheme ◽  
Thermomechanical Properties ◽  
Two Stage ◽  
Liquid Crystal Elastomers

Actuation temperature was controlled without influencing total actuation performance in liquid crystal elastomers fabricated by a two-stage reaction scheme.

One Methylene Group in the Side Chain Can Alter by 90 Degrees the Orientation of a Main-Chain Liquid Crystal on a Unidirectional Substrate

2018 ◽  
Vol 7 (4) ◽  
pp. 453-458
Author(s):  
Yaroslav Odarchenko ◽  
Matthieu Defaux ◽  
Martin Rosenthal ◽  
Azaliia Akhkiamova ◽  
Polina Bovsunovskaya ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Main Chain ◽  
Side Chain ◽  
Methylene Group

Unsymmetric main-chain liquid crystal elastomers with tunable phase behaviour: elastic response

2011 ◽  
Vol 21 (23) ◽  
pp. 8436 ◽  
Author(s):  
Maria Amela-Cortés ◽  
Duncan W. Bruce ◽  
Kenneth E. Evans ◽  
Christopher W. Smith
Keyword(s):  
Liquid Crystal ◽  
Main Chain ◽  
Phase Behaviour ◽  
Elastic Response ◽  
Liquid Crystal Elastomers
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