scholarly journals Nanostructured Composites Based on Liquid-Crystalline Elastomers

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 773 ◽  
Author(s):  
Vanessa Cresta ◽  
Giuseppe Romano ◽  
Alexej Kolpak ◽  
Boštjan Zalar ◽  
Valentina Domenici
Keyword(s):  
Liquid Crystalline ◽  
Carbon Nanomaterials ◽  
Chemical Characterization ◽  
Soft Materials ◽  
Thin Layers ◽  
Ferroelectric Ceramics ◽  
Magnetic Actuation ◽  
Magnetic Iron Oxide Nanoparticles ◽  
Graphene Layers ◽  
Optical Applications

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.

Designing Chemically Selective Liquid Crystalline Materials that Respond to Oxidizing Gases

2021 ◽  
Author(s):  
Nanqi Bao ◽  
Jake Gold ◽  
Tibor Szilvasi ◽  
Huaizhe Yu ◽  
Robert Twieg ◽  
...  
Keyword(s):  
Computational Methods ◽  
First Principles ◽  
Liquid Crystalline ◽  
Soft Materials ◽  
Crystalline Materials ◽  
Liquid Crystalline Materials ◽  
Chemically Selective ◽  
Kinetics Of

Computational methods can provide first-principles insights into the thermochemistry and kinetics of reactions at interfaces, but this capability has not been widely leveraged to design soft materials that respond selectively...

Thermal, Mechanical and Magneto-Mechanical Characterization of Liquid Crystalline Elastomers Loaded with Iron Oxide Nanoparticles

2015 ◽  
Vol 1718 ◽  
pp. 3-7
Author(s):  
Stephany Herrera-Posada ◽  
Barbara O. Calcagno ◽  
Aldo Acevedo
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Liquid Crystalline ◽  
Molar Mass ◽  
Oxide Nanoparticles ◽  
Magnetic Actuation ◽  
Scanning Calorimetry ◽  
Elastomeric Matrix ◽  
Alternating Magnetic Fields

ABSTRACTLiquid crystalline elastomers (LCEs) are materials that reveal unusual mechanical, optical and thermal properties due to their molecular orientability characteristic of low molar mass liquid crystals while maintaining the mechanical elasticity distinctive of rubbers. As such, they are considered smart shape-changing responsive systems. In this work, we report on the preparation of magnetic sensitized nematic LCEs using iron oxide nanoparticles with loadings of up to 0.7 wt%. The resultant thermal and mechanical properties were characterized by differential scanning calorimetry, expansion/contraction experiments and extensional tests. The magnetic actuation ability was also evaluated for the neat elastomer and the composite with 0.5 wt% magnetic content, finding reversible contractions of up to 23% with the application of alternating magnetic fields (AMFs) of up to 48 kA/m at 300 kHz. Thus, we were able to demonstrate that the inclusion of magnetic nanoparticles yields LCEs with adjustable properties that can be tailored by changing the amount of particles embedded in the elastomeric matrix, which can be suitable for applications in actuation, sensing, or as smart substrates.

Theoretical Modeling and Exact Solution for Extreme Bending Deformation of Hard-Magnetic Soft Beams

2020 ◽  
Vol 87 (4) ◽  
Author(s):  
Wei Chen ◽  
Lin Wang
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Exact Solutions ◽  
Flexible Electronics ◽  
Soft Materials ◽  
Theoretical Modeling ◽  
Magnetic Field Direction ◽  
Magnetic Actuation ◽  
Governing Equations ◽  
Analysis And Design

Abstract Hard-magnetic soft materials (HMSMs) manufactured by embedding hard-magnetic particles in soft materials belong to a new type of soft active materials. The abilities of fast and complicated transformations of hard-magnetic soft structures provide a promising technology for soft robotics, flexible electronics, and biomedical devices. It is significant to investigate the mechanical behaviors of hard-magnetic soft structures for their better applications. In this work, a hard-magnetic soft beam under an external magnetic field is theoretically modeled and the exact solutions for its mechanical responses are presented. First, the governing equations and boundary conditions are derived based on the principle of minimum potential energy. To solve the derived governing equations analytically, a new polynomial fitting model for hyperelastic materials is proposed for the hard-magnetic soft beam. Then, the exact solutions of a cantilevered hard-magnetic soft beam actuated by a uniform magnetic field in any direction are obtained. The newly derived exact solutions are further verified by comparing current results with those from recent simulations and experiments. For large bending angles up to 90 deg and extreme bending angle up to 180 deg, quite consistent agreement among exact solutions, numerical simulations, and experimental observations can be achieved. Finally, using our theoretical model, the deformation of the hard-magnetic soft beam actuated by magnetic fields in an arbitrary direction with non-zero magnetic declination is explored. When the magnetic actuation is increased from a small level gradually, the hard-magnetic soft beam deflects and it would undergo small, large, and extreme bending deformations in sequence. It is very interesting that, when the magnetic actuation is sufficiently large, the hard-magnetic soft beam is stretched and its centerline tends to align with the external magnetic field direction, implying that the hard-magnetic soft beam undergoes a uniaxial tension. The theoretical modeling and exact solutions for hard-magnetic soft beams are expected to be useful in the analysis and design of soft materials and structures.

A comparative study of side chain liquid crystalline polymers and their monomers designed for nonlinear optical applications

1991 ◽  
Vol 6 (3) ◽  
pp. 604-609 ◽  
Author(s):  
R.B. Findlay ◽  
T.J. Lemmon ◽  
A.H. Windle
Keyword(s):  
Transition Temperature ◽  
Liquid Crystalline ◽  
Nonlinear Optical ◽  
Liquid Crystalline Polymers ◽  
Significant Degree ◽  
Side Chain ◽  
Crystalline Polymers ◽  
Chemical Structures ◽  
Optical Applications ◽  
Nonlinear Optical Applications

Characterizations of side chain liquid crystalline polymers and their monomers point toward chemical structures and processing techniques which optimize their suitability for nonlinear optical applications. Polymers with methacrylate backbones and nitrostilbene or nitrobiphenyl side groups are studied; they tend to form smectic phases, but no solid crystallinity. By copolymerizing with nonmesogenic backbone units, the smectic-isotropic transition temperature can be controlled and may fall below the glass transition temperature. There is evidence for a significant degree of pretransitional alignment due to the surface fields, and mesogen ordering perpendicular to flow-induced backbone alignment. Very rapid cooling can suppress the highly scattering polydomain smectic phase.

A Novel Mechanism of Electrorheological Effect in Polymer Blends

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1983-1989 ◽  
Author(s):  
H. Kito ◽  
K. Tajiri ◽  
H. Orihara ◽  
Y. Ishibashi ◽  
M. Doi ◽  
...  
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
High Viscosity ◽  
Thin Layers ◽  
The Other ◽  
Parallel Plates ◽  
Low Viscosity ◽  
Electrorheological Effect ◽  
Er Fluid

We present a novel mechanism of an electrorheological (ER) effect found in a polymer blend of a liquid crystalline polymer (LCP) with high viscosity and a polydimethylsiloxane (DMS) with low viscosity. In this type of ER fluid thin layers of DMS are formed between the parallel plates of a viscometer and so the blends separated by them can slide on each other, resulting in the decrease of the apparent viscosity. Under an electric field, on the other hand, the area of the layers decreases and thus the ER effect appears.

Physico-chemical Characterization of Thin Oxide Films: Difficulties and Solutions

2008 ◽  
Vol 1073 ◽  
Author(s):  
Thierry Conard ◽  
Wilfried Vandervorst
Keyword(s):  
Substrate Surface ◽  
Depth Profiling ◽  
Chemical Characterization ◽  
Surface Preparation ◽  
High Energy ◽  
Thin Layers ◽  
Back Side ◽  
Gate Stack ◽  
Metal Gates

ABSTRACTOxides have always been an integral part of semiconductor manufacturing both in front and back-end processing. With the necessary increase in performance, the demand on these oxides has been increasing leading to their (future) replacement by more complex materials, such as high-k's in gate oxide and metal gates. With the increasing material complexity, a thorough characterization of all aspects of these materials is necessary, covering, for instance, surfaces and interfaces, nucleation, growth, atomic structure, …This article focuses on the characterization of front-end oxides and their interfaces. It shows that detailed information can be achieved by sophisticated experimental techniques such as synchrotron radiation, high energy ERD or AtomProbe but that adequate sample preparation and/or analysis by a combination of more routinely available techniques may achieve similar results. This is shown through the study of three different systems/problems in the gate stack analysis. We will first focus on the determination of substrate surface preparation conditions before deposition and their influence on growth mode and the growth characteristics by different growth techniques (ALD, MOCVD, …). Second, we present the possibilities of compositional depth profiling of thin layers both with nuclear techniques and Angle-Resolved XPS. Finally, we will show that using conventional XPS and a combination of front and back-side analysis, the interface between high-k oxide and metal gates can be investigated. More examples of gate stack characterization can be found elsewhere

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