Stress-strain and thermomechanical characterization of nematic to smectic A transition in a strongly-crosslinked bimesogenic liquid crystal elastomer

The actuation forces of a hydrophilic liquid crystal elastomer (LCE) in response to water vapor was tested and modeled. These materials exhibit asymmetric swelling as water vapor is absorbed into one side of the elastomer film. This gives rise to deflection away from the water source. Deformation due to water vapor has shown to be on the order of seconds and is reversible which provides unique sensing and actuation characteristics for elastomer films. The constitutive behavior is modeled by using nonlinear continuum mechanics to predict internal changes in density of the liquid crystal elastomer and subsequent deformation by correlating moisture exposure with changes in the elastomer’s density. In order to compare the model and obtain a set material parameters, a micro-Newton measuring device was designed and tested to quantify the forces generated in the liquid crystal elastomer under bending. Forces ranging between 1 to 8 μN were measured as a function of the location of the water vapor source. The results provide important insight into chemical force response and sensing for a number of biomedical and microfluidic applications.

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Synchrotron Microbeam Diffraction Studies on the Alignment within 3D-Printed Smectic-A Liquid Crystal Elastomer Filaments during Extrusion

Crystals ◽

10.3390/cryst11050523 ◽

2021 ◽

Vol 11 (5) ◽

pp. 523

Author(s):

Marianne E. Prévôt ◽

Senay Ustunel ◽

Benjamin M. Yavitt ◽

Guillaume Freychet ◽

Caitlyn R. Webb ◽

...

Keyword(s):

Liquid Crystal ◽

3D Printing ◽

Internal Structure ◽

Smart Materials ◽

Time Resolved ◽

Promote Cell Proliferation ◽

Liquid Crystal Elastomer ◽

Smectic A ◽

3D Printed ◽

Liquid Crystal Elastomers

3D printing of novel and smart materials has received considerable attention due to its applications within biological and medical fields, mostly as they can be used to print complex architectures and particular designs. However, the internal structure during 3D printing can be problematic to resolve. We present here how time-resolved synchrotron microbeam Small-Angle X-ray Diffraction (μ-SAXD) allows us to elucidate the local orientational structure of a liquid crystal elastomer-based printed scaffold. Most reported 3D-printed liquid crystal elastomers are mainly nematic; here, we present a Smectic-A 3D-printed liquid crystal elastomer that has previously been reported to promote cell proliferation and alignment. The data obtained on the 3D-printed filaments will provide insights into the internal structure of the liquid crystal elastomer for the future fabrication of liquid crystal elastomers as responsive and anisotropic 3D cell scaffolds.

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Chemical-Physical Characterization of a Binary Mixture of a Twist Bend Nematic Liquid Crystal with a Smectogen

Crystals ◽

10.3390/cryst10121110 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1110

Author(s):

Abir Aouini ◽

Maurizio Nobili ◽

Edouard Chauveau ◽

Philippe Dieudonné-George ◽

Gauthier Damême ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Nematic Liquid Crystal ◽

Liquid Crystalline ◽

Smectic A ◽

Liquid Crystalline Phases ◽

Electro Optic ◽

Optical Dielectric

Nematic twist-bend phases (NTB) are new types of nematic liquid crystalline phases with attractive properties for future electro-optic applications. However, most of these states are monotropic or are stable only in a narrow high temperature range. They are often destabilized under moderate cooling, and only a few single compounds have shown to give room temperature NTB phases. Mixtures of twist-bend nematic liquid crystals with simple nematogens have shown to strongly lower the nematic to NTB phase transition temperature. Here, we examined the behaviour of new types of mixtures with the dimeric liquid crystal [4′,4′-(heptane-1,7-diyl)bis(([1′,1″-biphenyl]4″-carbo-nitrile))] (CB7CB). This now well-known twist-bend nematic liquid crystal presents a nematic twist-bend phase below T ≈ 104 °C. Mixtures with other monomeric alkyl or alkoxy -biphenylcarbonitriles liquid crystals that display a smectic A (SmA) phase also strongly reduce this temperature. The most interesting smectogen is 4′-Octyl-4-biphenylcarbonitrile (8CB), for which a long-term metastable NTB phase is found at room and lower temperatures. This paper presents the complete phase diagram of the corresponding binary system and a detailed investigation of its thermal, optical, dielectric, and elastic properties.

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Synthesis and Characterization of Nonsymmetric Liquid Crystal Dimer Containing Biphenyl and Azobenzene Moiety

Journal of Chemistry ◽

10.1155/2013/939406 ◽

2013 ◽

Vol 2013 ◽

pp. 1-6 ◽

Cited By ~ 3

Author(s):

S. Sandy Subala ◽

B. Syama Sundar ◽

S. Sreehari Sastry

Keyword(s):

Liquid Crystal ◽

Liquid Crystalline ◽

Optical Microscope ◽

Synthesis And Characterization ◽

Spectroscopic Methods ◽

Liquid Crystal Phase ◽

Smectic A ◽

Smectic C ◽

Azobenzene Moiety

Calamitic liquid crystalline dimer containing azobenzene moiety and a decyloxy biphenyl linked by flexible spacers {4-[7-(4′-decyloxy-biphenyl-4-yloxy)-alkyloxy]-phenyl}-(4-decyl-phenyl)-diazene has been synthesized and characterized by spectroscopic methods. The transition temperatures and phase behaviours were studied by Differential Scanning Calorimeter (DSC) and Polarizing Optical Microscope (POM). The synthesized compounds exhibited enantiotropic liquid crystal phase with higher spacer display nematic and smectic C phases while lower spacer shows nematic and smectic A phases.

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