An innovative self‐healing polydimethylsiloxane (PDMS) elastomer, namely, PDMS‐TFB, is reported by incorporating the reversibly dynamic imine bond as the self‐healing points into the PDMS networks. ...The PDMS‐TFB elastomer features good optical transmittance (80%) in full visible light region, high stretchability (≈700%), and excellent autonomous self‐healing ability at room temperature. Surprisingly, the self‐healing behavior can take place in water and even at a temperature as low as −20 °C in air, showing a promising outlook for broader applications. As a proof‐of‐concept, this study demonstrates the use of the PDMS‐TFB elastomer for preparing anticorrosion coating and adhesive layer, and also the use of such an elastomer to be the platform for fabricating the flexible interconnector and chemical sensor. Remarkably, no significant difference is observed between the pristine and healed samples. Taking full advantage of these unique properties, it is anticipated that such a PDMS‐TFB elastomer shows wide applications in the fields of materials science, electronics, biology, optics, etc.
Autonomous self‐healing poly(dimethylsiloxane) elastomer with high optical transmittance (80%) and stretchability (≈700%) is prepared by simply mixing triformylbenzene and amine‐terminated poly(dimethylsiloxane), showing rapid and efficient self‐healing capability both in air and water over a broad temperature region. As a proof‐of‐concept, such an elastomer is used as the anticorrosion layer, reusable adhesive, and platforms for self‐healing and flexible interconnectors and chemical sensors.
Blends of poly(lactic acid) (PLA) and amine-terminated butadiene-acrylonitrile (ATBN) elastomer were prepared by solution with ATBN contents of 8-20 wt%. Films were molded by liquid deposition ...modeling 3D printing, Fourier transform infrared (FTIR) spectroscopy showed that the terminal carboxylic groups of the PLA chains reacted with the terminal amino groups of ATBN. Water was the byproduct of this reaction, causing PLA hydrolysis and accelerating the reaction. Thermogravimetric analysis (TGA) showed that components interaction caused a loss of PLA thermal stability. Scanning electron microscopy (SEM) of the blends revealed a porous morphology and no phase separation. There was change in the elongation when compared with neat PLA. Although the addition of a telechelic elastomer could improve PLA toughness, any benefits arising from such addition seem to be neutralized by PLA chain scission due to hydrolysis and porosity, resulting from the condensation reaction.
A new design strategy to produce a supramolecular elastomer with self‐healing and dielectric properties by synthesizing an aniline tetramer (AT)‐functionalized supramolecular elastomer (SE‐AT) is ...demonstrated. The termination of AT in the supramolecular system not only shortens linear amide molecular chain to decrease glass transition temperature but also destroys the crystallization to achieve amorphous structure. The SE‐AT provides two kinds of noncovalent bonding including π–π stacking and the hydrogen bond, which makes the material more easily healed. The SE‐AT20% can heal mechanical properties within 24 h at room temperature without any external stimulus. The dielectric constant shows a continuous increase overall with increasing AT content. The material exhibits good electro‐mechanical properties, which is attributed to a simultaneous increase in dielectric constant and decrease in modulus. The maximum actuated strain significantly increases with the increasing AT content and the SE‐AT20% reaches 10% at 1 V µm−1. Moreover, SE‐AT exhibits the ability to regain actuated strain on the location of the mechanical damage after self‐healing.
A new design strategy to produce a self‐healing dielectric elastomer by synthesizing an aniline tetramer(AT)‐functionalized supramolecular elastomer (SE‐AT) is demonstrated. The SE‐AT exhibits an excellent self‐healing capability at room temperature and outstanding electro‐mechanical property at low electric field. Moreover, SE‐AT exhibits the ability to regain actuated strain at electric fields after self‐healing.
Soft materials that respond to wireless external stimuli are referred to as “smart” materials due to their promising potential in real‐world actuation and sensing applications in robotics, ...microfluidics, and bioengineering. Recent years have witnessed a burst of these stimuli‐responsive materials and their preliminary applications. However, their further advancement demands more versatility, configurability, and adaptability to deliver their promised benefits. Here, a dual‐stimuli‐responsive soft bimorph material with three configurations that enable complex programmable 3D shape‐morphing is presented. The material consists of liquid crystal elastomers (LCEs) and magnetic‐responsive elastomers (MREs) via facile fabrication that orthogonally integrates their respective stimuli‐responsiveness without detrimentally altering their properties. The material offers an unprecedented wide design space and abundant degree‐of‐freedoms (DoFs) due to the LCE's programmable director field, the MRE's programmable magnetization profile, and diverse geometric configurations. It responds to wireless stimuli of the controlled magnetic field and environmental temperature. Its dual‐responsiveness allows the independent control of different DoFs for complex shape‐morphing behaviors with anisotropic material properties. A diverse set of in situ reconfigurable shape‐morphing and an environment‐aware untethered miniature 12‐legged robot capable of locomotion and self‐gripping are demonstrated. Such material can provide solutions for the development of future soft robotic and other functional devices.
A bimorph material with uncoupled integration of a magnetic‐responsive elastomer with a liquid crystal elastomer is reported. This material can be actuated by both magnetic and heat stimuli. It enables heterogenous material properties and local addressability for independent control of separate parts within a single device. It introduces a new dimension in the design and control of wireless soft machines.
An overview on the synthesis, properties, and applications of fluoropolymers (PFs) is presented. First, a non‐exhaustive summary on the homopolymers from conventional radical polymerization of ...fluoromonomers is proposed. FPs are interesting materials thanks to their outstanding properties such as thermal, oxidative and chemical resistances, low dissipation factor, refractive index, permittivity, and water absorptivity, as well as excellent durability and weatherability. Various strategies of synthesis are proposed, especially on recent studies on radical (co)polymerization of fluoroalkenes, just like their properties and applications ranging from coatings and energy‐related materials (e.g. fuel cell membranes, components for lithium ion batteries, electroactive devices, and photovoltaics) to original fluorinated elastomers, surfactants, thermoplastic elastomers, thermostables, and optical devices.
Finding places for fluorine: This review provides several recent innovative achievements from fluoropolymers: aerospace materials, thermoplastic elastomers, components for energy, coatings, optically and transparent films. An overview of the synthesis, properties, and applications of fluoropolymers is presented, firstly summarizing conventional strategies as well as RDRP (especially ITP, RAFT and CMRP) of fluorinated alkenes and secondly their design and applications as macromolecular materials.
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Ligaments and tendons are comprised of aligned, crimped collagen fibrils that provide tissue-specific mechanical properties with non-linear extension behaviour, exhibiting low stress ...at initial strain (toe region behaviour). To approximate this behaviour, we report fibrous scaffolds with sinusoidal patterns by melt electrowriting (MEW) below the critical translation speed (CTS) by exploitation of the natural flow behaviour of the polymer melt. More specifically, we synthesised photopolymerizable poly(L-lactide-co-ε-caprolactone-co-acryloyl carbonate) (p(LLA-co-ε-CL-co-AC)) and poly(ε-caprolactone-co-acryloyl carbonate) (p(ε-CL-co-AC)) by ring-opening polymerization (ROP). Single fibre (fØ = 26.8 ± 1.9 µm) tensile testing revealed a customisable toe region with Young’s Moduli ranging from E = 29 ± 17 MPa for the most crimped structures to E = 314 ± 157 MPa for straight fibres. This toe region extended to scaffolds containing multiple fibres, while the sinusoidal pattern could be influenced by printing speed. The synthesized polymers were cytocompatible and exhibited a tensile strength of σ = 26 ± 7 MPa after 104 cycles of preloading at 10% strain while retaining the distinct toe region commonly observed in native ligaments and tendon tissue.
Damaged tendons and ligaments are serious and frequently occurring injuries worldwide. Recent therapies, including autologous grafts, still have severe disadvantages leading to a demand for synthetic alternatives. Materials envisioned to induce tendon and ligament regeneration should be degradable, cytocompatible and mimic the ultrastructural and mechanical properties of the native tissue. Specifically, we utilised photo-cross-linkable polymers for additive manufacturing (AM) with MEW. In this way, we were able to direct-write cytocompatible fibres of a few micrometres thickness into crimp-structured elastomer scaffolds that mimic the non-linear biomechanical behaviour of tendon and ligament tissue.
4D‐Printing of Photoswitchable Actuators Lu, Xili; Ambulo, Cedric P.; Wang, Suitu ...
Angewandte Chemie International Edition,
March 1, 2021, Letnik:
60, Številka:
10
Journal Article
Recenzirano
Shape‐switching behavior, where a transient stimulus induces an indefinitely stable deformation that can be recovered on exposure to another transient stimulus, is critical to building smart ...structures from responsive polymers as continue power is not needed to maintain deformations. Herein, we 4D‐print shape‐switching liquid crystalline elastomers (LCEs) functionalized with supramolecular crosslinks, dynamic covalent crosslinks, and azobenzene. The salient property of shape‐switching LCEs is that light induces long‐lived, deformation that can be recovered on‐demand by heating. UV‐light isomerizes azobenzene from trans to cis, and temporarily breaks the supramolecular crosslinks, resulting in a programmed deformation. After UV, the shape‐switching LCEs fix more than 90 % of the deformation over 3 days by the reformed supramolecular crosslinks. Using the shape‐switching properties, we print Braille‐like actuators that can be photoswitched to display different letters. This new class of photoswitchable actuators may impact applications such as deployable devices where continuous application of power is impractical.
Shape‐switching liquid crystal elastomers are formulated where light is used to trigger a shape change which is then stable indefinitely. The original shape can be recovered on heating. These materials can be 4D printed into reconfigurable Braille‐like actuators capable of displaying letters “L”, “C” and “E” by switching the shape‐morphing of the Archimedean chord patterns with UV light and heating.
Polyolefin thermoplastic elastomers (TPE‐Os) are high‐performance polyolefins consisting of both plastic and rubber phases. Compared with other thermoplastic elastomers, the TPE‐Os possess better ...chemical stability, transparency, re‐processability, and electrical insulation, which renders their broad applications possible. By manipulating chain structures and topologies of the TPE‐Os, differently structured polyolefins with improved thermal and mechanical properties have been developed, including ethylene and α‐olefin random copolymers (POEs), olefin block copolymers (OBCs), comb‐shaped polyolefin elastomers (CPOEs), and dynamically cross‐linked polyolefin elastomers. Herein, we review the synthesis of the POE, OBC, CPOE, and dynamical cross‐linked polyolefin elastomer, including the catalyst systems, polymerization techniques, processes, and kinetic modelling. The characterization of the TPE‐Os and the relationships between the TPE‐O chain structure, aggregated state, and product performance are discussed. The future development of higher‐performance TPE‐Os is envisaged.
Development of high‐performance polyolefin thermoplastic elastomers from structure customization
Silicone elastomers are widely used in aviation, electronics, automotive, and medical device fields, and their overuse inevitably causes recycled problems. In addition, the elastomers are subject to ...attack by bacteria and fire during use in some application scenarios, which is a safety hazard. Therefore, there is a great need to prepare silicone elastomers with improved antibacterial, flame retardant, self‐healing, and recyclable functions. A new strategy is proposed to prepare silicone elastomers with bio‐based tannic acid as cross‐linkers to solve this problem by using polydimethylsiloxane as a soft chain segment and 2,2‐bis(hydroxymethyl)propionic acid as an intermediate chain extender. Based on the phenol carbamate bonding and hydrogen bonding interactions, the elastomer has efficient self‐healing ability and can achieve dynamic dissociation at 120 °C for complete recovery. In addition, due to the unique spatial structure and polyphenolic hydroxyl groups of tannic acid, the mechanical properties of the elastomer are greatly improved with an antimicrobial efficiency of over 90% and a final oxygen index of 25.5%. The multifunctional silicone elastomer has great potential applications in recyclable refractory materials and antimicrobial materials.
A new strategy is proposed to prepare silicone elastomers with bio‐based tannic acid as cross‐linkers. The elastomer has efficient self‐healing ability and can achieve dynamic dissociation at 120 °C for complete recovery. The mechanical properties of the elastomer are greatly improved with an antimicrobial efficiency of over 90% and a final oxygen index of 25.5%.
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