A catalyst-free malleable network polymer that can be reprocessed by application of either water or heat is prepared through imine chemistry. This material recycled from a fine powder to coherent solid with >100% recycling efficiency several generations. It also at ambient temperature using only water, thus potentially leading energy-neutral green processing the material.

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% the imine components and carbon fibers in their original form. Polyimine films made >21% recycled content exhibit no loss mechanical performance, therefore indicating all thermoset composite material can be reused for same purpose. As a service to our authors readers, this journal provides...

Abstract Folding is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It finds technological applications including packaging solar cells and space structures, deployable biomedical devices self-assembling robots airbags. Here we demonstrate sequential self-folding structures realized by thermal activation spatially-variable patterns that are 3D printed digital shape memory polymers, which materials different behaviors. The time-dependent...

Both environmental and economic factors have driven the development of recycling routes for increasing amount composite waste generated. This paper presents a new paradigm to fully recycle epoxy‐based carbon fiber reinforced polymer (CFRP) composites. After immersing in ethylene glycol (EG) temperature, epoxy matrix can be dissolved as EG molecules participate bond exchange reactions (BERs) within covalent adaptable network (CAN), effectively breaking long chains into small segments. The...

An epoxy ink and its 3D printing method were developed to allow printed parts be recycled reprinted.

In this work, we advance printed active composites by combining 3D printing, electronics, and liquid crystal elastomers (LCEs) to achieve soft actuators with free-standing two-way shape changing behaviors. Incorporated LCE strips are activated Joule heating produced conductive wires, while uniaxial deformation of the strip is utilized as a driving force bending in composite. The behavior laminated hinges first characterized order obtain precise control actuation, which then exploited actuate...

Liquid crystal elastomers (LCEs) are a unique class of materials that combine rubber elasticity with liquid crystalline anisotropy to produce exceptional physical and optical properties such as actuation, soft elasticity, birefringence. This review gives brief overview the physics behind crystals classifications LCEs before discussing methods traditionally used synthesize LCEs, new synthesis have emerged within past several years, developing applications LCEs. The begins by organization in...

A method for fabricating long, soft, and reversibly actuatable liquid crystal elastomer (LCE) fibers by using direct ink write (DIW) printing was developed. Here, the LCE produced based on a two-stage thermal-photo curing reaction between difunctional acrylate monomer thiol. The ink, mixed with nanoclay to increase viscosity, extruded through nozzle onto rotating mandrel obtain long fiber. After printing, fiber first thermally cured mandrel, then mechanically stretched, photocured achieve...

In this paper, we experimentally demonstrated the reprocessing, recycling and repairing abilities of pulverized thermoset polymer with exchangeable bonds.

In this paper, we demonstrate the feasibility of using 3D printing technique to create functional graded shape memory polymers (SMPs) with both spontaneous and sequential recovery abilities. The created SMP components, properly assigned spatial variation thermodynamical property distribution, react rapidly a thermal stimulus, return specified configuration in precisely controlled changing sequence. use enables manufacturing routine merits easy implementation, large design freedom, high...

Covalent adaptable networks (CANs; also known as dynamic covalent or vitrimers) are appealing for developing simple and efficient techniques recycling thermosetting polymers. In this paper, ethylene glycol (EG) is used a solvent to enable pressure-free surface welding, repair, of malleable epoxy where the transesterification-type bond exchange reaction (BER) imparts nature network. At high temperature, EG molecules participate in BER, leading dissolution If allowed evaporate, dissolved can...

Abstract Digital Light Processing (DLP) 3D printing enables the creation of hierarchical complex structures with specific micro‐ and macroscopic architectures that are impossible to achieve through traditional manufacturing methods. Here, this hierarchy is extended mesoscopic length scale for optimized devices dissipate mechanical energy. A photocurable, thus DLP‐printable main‐chain liquid crystal elastomer (LCE) resin reported used print a variety complex, high‐resolution...

Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy ideally absorbed at constant stress. Conventionally, compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large devices. Here, we use direct-ink writing 3D printing to fabricate bulk (>cm3) LCE devices study their soft-elasticity over 8 decades of rate. At quasi-static rates, soft-elastic...

Covalent adaptable networks (CANs) represent a novel class of polymeric materials crosslinked by dynamic covalent bonds. Since their first discovery, CANs have attracted great attention due to high mechanical strength and stability like conventional thermosets under service conditions easy reprocessability thermoplastics certain external stimuli. Here, we report the example ionic (ICANs), type ionomers, consisting negatively charged backbone structures. More specifically, two ICANs with...

Shape memory polymers have attracted increasing research interest due to their capability of fixing a temporary shape and associated deformation energy then releasing them later on demand. Recently, it has been reported that with broad thermomechanical transition temperature range can demonstrate multi-shape effect (m-SME), where recovery release occur in stepped manner during free recovery. This paper investigated the underlying physical mechanisms for these observed behaviors storage by...

Thermally malleable polymers which undergo covalent bond exchange reactions (BERs) have been shown to be able rearrange their network topology at high temperatures without impairing the integrity. At low temperatures, BERs are so sluggish that materials behave like traditional thermosetting polymers. In this paper, we demonstrated temperature dependent BER rate could tuned by adjusting stoichiometry of monomers. As ratio hard segments in epoxy thermoset is increased, material's glass...

In this paper, the practicability of actuating shape recovery thermo-responsive memory polymers (SMPs) filled with carbon nanotubes (CNTs) has been investigated. When exposed to microwave radiation, embedded CNTs were expected absorb external electromagnetic energy and act as node heating sources in SMP/CNT composites. way, SMP could be volumetrically heated subsequently would lead a fast actuation. Although pure was not responsive absorption ratio composites significantly increased along...

Adaptable liquid crystal elastomers (LCEs) have recently emerged to provide a new and robust method program monodomain LCE samples. When constant stress is applied with active bond exchange reactions (BERs), polymer chains mesogens gradually align in the strain direction. Mesogen alignment maintained after removing BER stimulus (e.g. by lowering temperature) programmed samples exhibit free-standing two-way shape switching behavior. Here, adaptable main-chain system was developed thermally...

Abstract Shape memory polymers (SMPs) can be programmed to a temporary shape, and then recover its original shape by applying environmental stimuli when needed. To expands the application space of SMPs, polymer composites (SMPCs) were fabricated either improve mechanical properties, or incorporate more stimulus methods. With deepening research, filler arrangement also used reshape from two dimensional sheet three structure strain mismatch. Recently, SMPCs show interesting behaviors. gain...

Polymer foams are an essential class of lightweight materials used to protect assets against mechanical insults, such as shock and vibration. Two features important enhance their energy absorption characteristics: the foam structure matrix phase behavior. This study investigates novel approaches control both these capability flexible lattice foams. First, we consider 3D printing via digital light processing (DLP) a method mesostructure across suite periodic unit cells. Second, introduce...

Abstract Reversible programming of 3D soft mesostructures is desired for many applications including robotics and biomedical devices. The large, reversible shape changes liquid crystal elastomers (LCEs), which result from the coupling between alignment (LC) molecules macroscopic deformation polymer networks, have attracted much attention such applications. Here, a facile versatile strategy introduced to create reconfigurable, freestanding LCEs magnetic LCE composites that are inaccessible...