Liquid‐Crystalline Elastomer‐Nanoparticle Hybrids with Reversible Switch of Magnetic Memory

Haberl, Johannes M.; Sánchez‐Ferrer, Antoni; Mihut, Adriana M.; Dietsch, Hervé; Hirt, Ann M.; Mezzenga, Raffaele

doi:10.1002/adma.201204406

Cited by 104 publications

(82 citation statements)

References 31 publications

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“…2,3 Liquid crystalline elastomers (LCE) represent a special class of SMPs that are defined by a reversible LC phase transition and a unique coupling between LC mesogens and polymer networks. They exhibit reversible shape change when exposed to external stimuli, such as heat, 4 light, 5−8 or magnetic field, 9,10 which makes them excellent candidates for artificial muscles, sensors, lithography substrates, and shape memory materials. 11−16 A number of LCEs with different LC phases and network structures have been synthesized and characterized, including nematic main-chain, 17−19 smectic main-chain, 20,21 nematic sidechain, 22,23 and smectic side-chain LCEs.…”

Section: ■ Introductionmentioning

confidence: 99%

Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

Pruitt

Rios³

et al. 2015

Macromolecules

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A smectic main-chain liquid crystalline elastomer (LCE), with controlled shape memory behavior, is synthesized by polymerizing a biphenyl-based epoxy monomer with an aliphatic carboxylic acid curing agent. Microstructures of the LCEs, including their liquid crystallinity and crosslinking density, are modified by adjusting the stoichiometric ratio of the reactants to tailor the thermomechanical properties and shape memory behavior of the material. Thermal and liquid crystalline properties of the LCEs, characterized using differential scanning calorimetry and dynamic mechanical analysis, and structural analysis, performed using small-angle and wide-angle X-ray scattering, show that liquid crystallinity, cross-linking density, and network rigidity are strongly affected by the stoichiometry of the curing reaction. With appropriate structural modifications it is possible to tune the thermal, dynamic mechanical, and thermomechanical properties as well as the shape memory and thermal degradation behavior of LCEs. ■ INTRODUCTIONShape memory polymers (SMP) are a category of smart materials that are able to return to their original shape from a deformed state when exposed to external stimuli. SMPs generally consist of cross-linked polymer networks, which determine the permanent shape of the material, and switching segments, which can be oriented and solidified to fix a temporary shape. 1 The shape recovery is driven by the entropic force of the switching domains which tend to gain entropy and return to a random conformation when undergoing phase transitions, such as glass transition, liquid crystalline (LC) transition, and melting transition. 2,3 Liquid crystalline elastomers (LCE) represent a special class of SMPs that are defined by a reversible LC phase transition and a unique coupling between LC mesogens and polymer networks. They exhibit reversible shape change when exposed to external stimuli, such as heat, 4 light, 5−8 or magnetic field, 9,10 which makes them excellent candidates for artificial muscles, sensors, lithography substrates, and shape memory materials. 11−16 A number of LCEs with different LC phases and network structures have been synthesized and characterized, including nematic main-chain, 17−19 smectic main-chain, 20,21 nematic sidechain, 22,23 and smectic side-chain LCEs. 24−26 These materials exhibit a wide variety of shape memory and actuating behaviors. However, in spite of their promising properties and remarkable potential, practical applications of LCEs are limited because of the difficulties encountered when tailoring thermal transition temperatures and thermomechanical properties of the materials for end-use applications. Several methods have been proposed to prepare LCEs with tunable shape memory properties. A smectic main-chain LCE has been designed and synthesized through copolymerization of two benzoate-based vinyl monomers with different LC phase transition temperatures. 27 It has been shown that both LC transition and thermomechanical properties of LCEs could be tailored by changing the ...

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Section: ■ Introductionmentioning

confidence: 99%

Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

Pruitt

Rios³

et al. 2015

Macromolecules

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“…The red arrow is the X-ray beam direction. (c) Schematic representation of the magnetic susceptibility components in the OFF and ON states (adapted with permission from Haberl et al 2013a) be magnetically read out; this kind of materials pave the way towards applications such as strain sensors or magnetic switches.…”

Section: Hybrid Liquid Crystalline Polymers and Elastomers For Soft Amentioning

confidence: 99%

Liquid Crystalline Polymers as Tools for the Formation of Nanohybrids

Lonetti

Mauzac

Mingotaud

et al. 2015

Liquid Crystalline Polymers

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“…Therefore, the inorganic-incorporated shape memory materials emerged and are developed dramatically. Various inorganic fillers such as carbon nanotubes (CNTs) [12][13][14], Fe 3 O 4 [15][16][17], SiO 2 [18][19][20], glass fibers [21], nanoclay [22], polyhedral oligomeric silsesquioxane (POSS) [23][24][25] have been incorporated to improve the mechanical and shape memory properties of SMPs.…”

Section: Introductionmentioning

confidence: 99%

Polyurethane/polyhedral oligomeric silsesquioxane shape memory nanocomposites with low trigger temperature and quick response

Jin

Liu

2015

J Polym Res

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Ester-based polyurethane (PU) was found to have excellent shape memory properties with low trigger temperature. Polyhedral oligomeric silsesquioxanes (POSS) have drawn considerable interest due to their hybrid organic-inorganic structures consisting of a silica cage surrounded by eight organic groups. Incorporation of functional POSS in polymers normally improves the mechanical properties of polymer matrix. For the purpose of obtaining shape memory materials with low trigger temperature and quick response, octa(3-hydroxypropyl) polyhedral oligomeric silsesquioxane (POSS-(OH) 8 ) was incorporated into polyurethane by solution casting. The chemical structures and microstructures were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) and field emission scanning electron microscope (FESEM). The thermal properties and dynamic mechanical properties were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties were also evaluated. Shape memory properties were characterized by cyclic thermal mechanical tests and physical shape recovery tests. The results show that the nanocomposites with low POSS-(OH) 8 loading content (1 and 3 wt.%) possess higher breaking strength and elastic modulus, resulting in higher shape fixity, recovery ratios and faster recovery. The nanocomposites might have potential applications for controlling tags or proof marks in the area of low temperature storage.

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Liquid‐Crystalline Elastomer‐Nanoparticle Hybrids with Reversible Switch of Magnetic Memory

Cited by 104 publications

References 31 publications

Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

Liquid Crystalline Polymers as Tools for the Formation of Nanohybrids

Polyurethane/polyhedral oligomeric silsesquioxane shape memory nanocomposites with low trigger temperature and quick response

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