Mouldable liquid-crystalline elastomer actuators with exchangeable covalent bonds

Pei, Zhiqiang; Yang, Yang; Chen, Qiaomei; Terentjev, Eugene M.; Wei, Yen; Ji, Yan

doi:10.1038/nmat3812

Cited by 741 publications

(624 citation statements)

References 33 publications

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“…11 Recent work has explored new methods to help overcome these challenges, such as using exchangeable crosslinks to be able to reprogram an aligned monodomain multiple times. 33 The purpose of this study was to present a relatively unexplored approach to LCE synthesis and monodomain programming using a two-stage TAMAP reaction. The first-stage reaction is a "click" reaction based on a thiol-acrylate Michael addition using an amine catalyst.…”

Section: Discussionmentioning

confidence: 99%

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

Saed

Torbati

Nair

et al. 2016

JoVE

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This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquidcrystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

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Section: Discussionmentioning

confidence: 99%

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

Saed

Torbati

Nair

et al. 2016

JoVE

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“…More recently malleable thermosets, also called covalently adaptive networks or vitrimers, have emerged as novel recyclable covalent network materials, which incorporate dynamically exchangeable covalent bonds into the polymer networks. [17][18][19][20] The rate of bond exchange exhibits an Arrhenius-like temperature dependence, enabling molding, welding, and complete recycling of the pure polymeric materials, while maintaining the crosslink density of the covalently adaptive network. [ 17,21,22 ] However, the recycling of vitrimers typically requires a mechanical process of abrasive grinding, followed by compression molding of the powdered binder above its vitrimeric transition temperature ( T v ).…”

Section: Doi: 101002/adma201505245mentioning

confidence: 99%

Repairable Woven Carbon Fiber Composites with Full Recyclability Enabled by Malleable Polyimine Networks

et al. 2016

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Carbon-fiber reinforced composites are prepared using catalyst-free malleable polyimine networks as binders. An energy neutral closed-loop recycling process has been developed, enabling recovery of 100% of the imine components and carbon fibers in their original form. Polyimine films made using >21% recycled content exhibit no loss of mechanical performance, therefore indicating all of the thermoset composite material can be recycled and reused for the same purpose.

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“…Many biological systems such as Escherichia coli (10), cilia (11), or nematocysts (12) provide sophisticated models for nanomachines (13). Although molecular motors and artificial muscles from hydrogels (14,15), colloids (16), or liquid crystalline elastomers (17,18) successfully mimic such behaviors, they are very slow (on the order of seconds) and the forces generated are very small (∼ pN). This is because either the energy density stored in the system is low or the energy release is inefficient.…”

mentioning

confidence: 99%

Light-induced actuating nanotransducers

Ding

Valev

Salmon

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

152

149

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Nanoactuators and nanomachines have long been sought after, but key bottlenecks remain. Forces at submicrometer scales are weak and slow, control is hard to achieve, and power cannot be reliably supplied. Despite the increasing complexity of nanodevices such as DNA origami and molecular machines, rapid mechanical operations are not yet possible. Here, we bind temperatureresponsive polymers to charged Au nanoparticles, storing elastic energy that can be rapidly released under light control for repeatable isotropic nanoactuation. Optically heating above a critical temperature T c = 32°C using plasmonic absorption of an incident laser causes the coatings to expel water and collapse within a microsecond to the nanoscale, millions of times faster than the base polymer. This triggers a controllable number of nanoparticles to tightly bind in clusters. Surprisingly, by cooling below T c their strong van der Waals attraction is overcome as the polymer expands, exerting nanoscale forces of several nN. This large force depends on van der Waals attractions between Au cores being very large in the collapsed polymer state, setting up a tightly compressed polymer spring which can be triggered into the inflated state. Our insights lead toward rational design of diverse colloidal nanomachines.ctuators are needed to turn energy sources into physical movement. These can be for microrobotics, sensing, storage devices, smart windows and walls, or more general functional and active materials. Such artificial muscles have gained rapidly increasing interest (1, 2) leading to micropropellers (3, 4), gas jets from catalytic surfaces (5), and DNA machines (6). However, the actuation methods, delivery of energy, and forces obtained (typically 10 fN/nm 2 ) are limited so far (7): Magnetic fields are inconvenient to apply locally for actuation, as is >200°C heating to actuate polymer fibers; the nanocatalysis of chemical fuels lacks controllability, whereas DNA machines rely on "fuel" DNA strands to competitively bind and operate on very slow (second) timescales. Piezoelectric-type materials used in high-end instrumentation (such as atomic force microscopy or nanopositioning stages) provide short travel but with inorganic materials that are dense, delicate, expensive, hard to fabricate, and demand high voltages (150-300 V), as is also true for electrostrictive rubbers and relaxor ferroelectrics (8, 9). Many biological systems such as Escherichia coli (10), cilia (11), or nematocysts (12) provide sophisticated models for nanomachines (13). Although molecular motors and artificial muscles from hydrogels (14, 15), colloids (16), or liquid crystalline elastomers (17, 18) successfully mimic such behaviors, they are very slow (on the order of seconds) and the forces generated are very small (∼ pN). This is because either the energy density stored in the system is low or the energy release is inefficient.To overcome this we design a colloidal actuating transducer system with high-energy storage (1,000 k B T/cycle) and fast (>MHz) release mechanism....

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Mouldable liquid-crystalline elastomer actuators with exchangeable covalent bonds

Cited by 741 publications

References 33 publications

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

Repairable Woven Carbon Fiber Composites with Full Recyclability Enabled by Malleable Polyimine Networks

Light-induced actuating nanotransducers

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