Durable liquid-crystalline vitrimer actuators

Programmable Complex Shape Changing of Polysiloxane Main-Chain Liquid Crystalline Elastomers

Liquid crystal elastomers (LCEs) are shape-morphing materials whose large and reversible shape transformations are caused by the coupling between the mobile anisotropic properties of liquid crystal (LC) units and the rubber elastic of polymer networks. Their shape-changing behaviors under certain stimuli are largely directed by the LC orientation; therefore, various strategies have been developed to spatially modulate the LC alignments. However, most of these methods are limited as they require complex fabrication technologies or have intrinsic limitations in applicability. To address this issue, programmable complex shape changes in some LCE types, such as polysiloxane side-chain LCEs, thiol-acrylate main-chain LCEs, etc., were achieved by using a mechanical alignment programming process coupled with two-step crosslinking. Here, we report a polysiloxane main-chain LCE with programmable 2- and 3D shape-changing abilities that were created by mechanically programming the polydomain LCE with two crosslinking steps. The resulting LCEs exhibited a reversible thermal-induced shape transformation between the initial and programmed shapes due to the two-way memory between the first and second network structures. Our findings expand on the applications of LCE materials in actuators, soft robotics, and smart structures where arbitrary and easily programmed shape morphing is needed.

Enabling liquid crystal elastomers with tunable actuation temperature

Liquid crystalline elastomers are regarded as a kind of desirable soft actuator material for soft robotics and other high-tech areas. The isotropization temperature (T_i) plays an important role as it determines the actuation temperature and other properties, which in turn has a great effect on their applications. In the past, the common physical methods (e.g. annealing) to tune T_i is not applicable to tune the actuation temperature. The new T_i obtained by annealing immediately goes back to the old one once it is heated to a temperature above T_i, while actuation needs a temperature higher than T_i. For a fully cross-linked LCE material, once it is synthesized, the actuation temperature is fixed. Accordingly, the actuation temperature can not be tuned unless the chemical structure is changed, which usually needs to start from the very beginning of the molecular design and material synthesis. Here, we found that different T_i achieved by annealing can be preserved by reversible reactions of dynamic covalent bonds in covalently adaptable LC networks including LC vitrimers. Thus, a variety of soft actuators with different actuation temperatures can be obtained from the same fully cross-linked LCE material. As the tuning of T_i is also reversible, the same actuator can be adjusted for applications with different actuation temperature requirements. Such tuning will also expand the application of LCEs.

Fabricating liquid crystal vitrimer actuators far below the normal processing temperature

Liquid crystal vitrimers can be reprocessed, reshaped, welded, and healed due to exchange-reaction-enabled topology changes despite having fully covalently cross-linked network structures. Fabricating liquid crystal (LC) vitrimer actuators is invariably carried out above a characteristic temperature known as the topology freezing transition temperature (T_v). The reason that all exchange-reaction-based operations must be performed above T_v is because the exchange reaction is insignificant below T_v. Here we find that LC vitrimers can be reshaped at temperatures below the measured T_v, whereas non-LC vitrimers cannot. The work here not only makes it possible to create reprogrammable and stable LC vitrimer actuators at low temperatures but also reminds us that both our measurement and understanding of the T_v need further attention to facilitate the use of vitrimers in different areas.

Magnetic-responsive Covalent Adaptable Networks

Covalent adaptable networks (CANs) are reprocessable polymers whose structural arrangement is based on the recombination of dynamic covalent bonds. Composite materials prepared by incorporating magnetic particles into CANs attract much attention due to their remote and precise control, fast response speed, high biological safety and strong penetration of magnetic stimuli. These properties often involve magnetothermal effect and direct magnetic-field guidance. Besides, some of them can also respond to light, electricity or pH values. Thus, they are favorable for soft actuators since various functions are achieved such as magnetic-assisted self-healing (heating or at ambient temperature), welding (on land or under water), shape-morphing, and so on. Although magnetic CANs just start to be studied in recent two years, their advances are promised to expand the practical applications in both cutting-edge academic and engineering fields. This review aims to summarize recent progress in magnetic-responsive CANs, including their design, synthesis and application.

Reprocessable and Chemically Recyclable Hard Vitrimers Based on Liquid-Crystalline Epoxides

The rapid increase in demand for recyclable and reusable thermosets has necessitated the development of materials with chemical structures that exhibit these features. Thus, functional mesogenic epoxide monomers bearing both ester and imine groups that can be vitrimerized and recycled are reported herein. The compounds show mesophase characteristics at 100-200 °C and can be converted into hard epoxides by a common curing reaction. The obtained hard epoxides have high isotropic thermal conductivity (≈0.64 W m^-1 K^-1 ), which is derived from their highly ordered microstructures. The cured products can be easily reprocessed through imine metathesis and transesterification, and decomposed products can be obtained through imine hydrolysis under acidic or basic conditions and subsequently be re-cured. Surprisingly, recycled materials can be repeatedly reprocessed or chemically decomposed. The reprocessed materials retain the properties of their pristine counterparts, and the recycled products preserve the advantages of the hard thermosets without alteration to any of their unique properties. A dehydration reaction occurs between the residual hydroxyl groups during the re-hardening, which dramatically increases the glass transition temperature by ≈60 °C. These reprocessable and recyclable vitrimers demonstrate the effectiveness and environmental friendliness of the molecular design strategy reported herein.

Optical wavelength selective actuation of dye doped liquid crystalline elastomers by quasi-daylight

We explore obtaining different photo responses of liquid crystalline elastomer (LCE) materials through modulating the optical wavelengths in order to promote the development of precise photocontrol on LCE actuators, and thus study the effect of light-absorbing dyes with different absorption bands on the selective actuation of LCE materials. The dye-doped LCEs were prepared by incorporating special visible absorber dyes into thiol-acrylate main chain LCE (MC-LCE) matrices. The dyes showed photo actuation performance to LCEs due to the photothermal effects. But, every dye-doped LCE could be effectively actuated by light irradiation whose wavelength was inside its absorption band, but could not be effectively actuated by the light whose wavelength was beyond its absorption band. Wavelength selective actuation effects, no matter actuating deformation or actuating force, could be remarkably demonstrated by these dye-doped LCEs through filtering the same quasi-daylight source to be different wavelength bands. Our work opens up a significant way for the precise and convenient photo actuation of LCE actuators, while expanding the utilization potential of quasi-daylight, and further natural sunlight.

Reconfigurable Fluorescent Liquid Crystal Elastomers for Integrated Visual and Haptic Information Storage

The rapid advancements in information technology require new information storage and display materials. However, the development of on-demand information storage systems with multiple modes remains a significant challenge. As a pioneering approach, this study designed an integrated visual and haptic information storage and display using a reconfigurable fluorescent liquid crystal elastomer (FLCE) with dynamic covalent bonds. The FLCEs were fabricated in two steps of amine-acrylate aza-Michael addition and photopolymerization, and they simultaneously exhibited phototunable fluorescence caused by the reversible Z/E photoisomerization of the chromophores and a reprogrammable shape owing to the catalyst-free transesterification. In addition, we established various information storage and display modes featuring the characteristics of reversibly photoswitchable fluorescence, shape memory, and thermally reconfigurable shape with a reconfigurable FLCE system. Moreover, a strategy to display the information by incorporating both visual and haptic feedback is implemented for fulfilling the needs of the visually impaired and related users. Such reconfigurable FLCE systems will aid in the development of on-demand information storage, display, and protection devices.

Locally controllable magnetic soft actuators with reprogrammable contraction-derived motions

Reprogrammable magneto-responsive soft actuators capable of working in enclosed and confined spaces and adapting functions under changing situations are highly demanded for new-generation smart devices. Despite the promising prospect, the realization of versatile morphing modes (more than bending) and local magnetic control remains challenging but is crucial for further on-demand applications. Here, we address the challenges by maximizing the unexplored potential of magnetothermal responsiveness and covalent adaptable networks (CANs) in liquid crystalline elastomers (LCEs). Various magneto-actuated contraction-derived motions that were hard to achieve previously (e.g., bidirectional shrinkage and dynamic 3D patterns) can be attained, reprogrammed, and assembled seamlessly to endow functional diversity and complexity. By integration of LCEs with different magneto-responsive threshold values, local and sequential magnetic control is readily realized. Many magnetic actuation portfolios are performed by rationally imputing "logic switch" sequences. Meanwhile, our systems exhibit additional favorable performances including stepwise magnetic controllability, multiresponsiveness, self-healing, and remolding ability.

Vitrimers: Using Dynamic Associative Bonds to Control Viscoelasticity, Assembly, and Functionality in Polymer Networks

Vitrimers have been investigated in the past decade for their promise as recyclable, reprocessable, and self-healing materials. In this Viewpoint, we focus on some of the key open questions that remain regarding how the molecular-scale chemistry impacts macroscopic physical chemistry. The ability to design temperature-dependent complex viscoelastic spectra with independent control of viscosity and modulus based on knowledge of the dynamic bond and polymer chemistry is first discussed. Next, the role of dynamic covalent chemistry on self-assembly is highlighted in the context of crystallization and nanophase separation. Finally, the ability of dynamic bond exchange to manipulate molecular transport and viscoelasticity is discussed in the context of various applications. Future directions leveraging dynamic covalent chemistry to provide insights regarding fundamental polymer physics as well as imparting functionality into polymers are discussed in all three of these highlighted areas.

Exchangeable Liquid Crystalline Elastomers and Their Applications

This Review presents and discusses the current state of the art in "exchangeable liquid crystalline elastomers", that is, LCE materials utilizing dynamically cross-linked networks capable of reprocessing, reprogramming, and recycling. The focus here is on the chemistry and the specific reaction mechanisms that enable the dynamic bond exchange, of which there is a variety. We compare and contrast these different chemical mechanisms and the key properties of their resulting elastomers. In the conclusion, we discuss the most promising applications that are enabled by dynamic cross-linking and present a summary table: a library of currently available materials and their main characteristics.

A simple, efficient route to modify the properties of epoxy dynamic polymer networks

A simple and efficient strategy to modify epoxy dynamic polymer networks (DPNs) is presented. The introduction of the flexible epoxidized form of naturally occurring soybean oil (ESO) into epoxy DPNs markedly improves their mechanical properties, stress relaxation rate and malleability. Specifically, at 7.5 wt% ESO loading, the elongation at break of the as-produced epoxy-ESO DPNs was increased from 10% to 108%, the stress relaxation time decreased from 6100 s to 2570 s at 120 °C, and the reprocessing temperature was reduced by 26 °C, which is advantageous for expanding the scope of applications of these materials, especially for reducing the energy consumption during reprocessing. At this composition, the epoxy-ESO DPNs also showed excellent self-healing, welding and chemical degradation properties. This work provides a novel pathway to fabricate epoxy-based DPNs with high performance in an energy-conserving manner.

Biomimetic Prosthetic Hand Enabled by Liquid Crystal Elastomer Tendons

As one of the most important prosthetic implants for amputees, current commercially available prosthetic hands are still too bulky, heavy, expensive, complex and inefficient. Here, we present a study that utilizes the artificial tendon to drive the motion of fingers in a biomimetic prosthetic hand. The artificial tendon is realized by combining liquid crystal elastomer (LCE) and liquid metal (LM) heating element. A joule heating-induced temperature increase in the LCE tendon leads to linear contraction, which drives the fingers of the biomimetic prosthetic hand to bend in a way similar to the human hand. The responses of the LCE tendon to joule heating, including temperature increase, contraction strain and contraction stress, are characterized. The strategies of achieving a constant contraction stress in an LCE tendon and accelerating the cooling for faster actuation are also explored. This biomimetic prosthetic hand is demonstrated to be able to perform complex tasks including making different hand gestures, holding objects of different sizes and shapes, and carrying weights. The results can find applications in not only prosthetics, but also robots and soft machines.

Sugarcane Bagasse-Derived Activated Carbon- (AC-) Epoxy Vitrimer Biocomposite: Thermomechanical and Self-Healing Performance

Vitrimeric materials have emerged as fascinating and sustainable materials owing to their malleability, reprocessability, and recyclability. Sustainable vitrimeric materials can be prepared by reinforcing polymeric matrix with bioderived fillers. In the current work, a sustainable vitrimer is prepared by incorporating biomass-derived activated carbon (AC) filler into the epoxy matrix to achieve enhanced thermal and mechanical properties. Thus, prepared biocomposite vitrimers demonstrate a lower-temperature self-healing (70°C for 5 min) via disulfide exchanges, compared to the pristine epoxy vitrimers (80°C for 5 min). Significantly, the self-healing performances have been studied extensively with the flexural studies; and changes in material healing efficiency have been demonstrated based on the observed changes in modulus.

Dually Crosslinked Polymer Networks Incorporating Dynamic Covalent Bonds

Covalent adaptable networks (CANs) are polymeric networks containing covalent crosslinks that are dynamic under specific conditions. In addition to possessing the malleability of thermoplastics and the dimensional stability of thermosets, CANs exhibit a unique combination of physical properties, including adaptability, self-healing, shape-memory, stimuli-responsiveness, and enhanced recyclability. The physical properties and the service conditions (such as temperature, pH, and humidity) of CANs are defined by the nature of their constituent dynamic covalent bonds (DCBs). In response to the increasing demand for more sophisticated and adaptable materials, the scientific community has identified dual dynamic networks (DDNs) as a promising new class of polymeric materials. By combining two (or more) distinct crosslinkers in one system, a material with tailored thermal, rheological, and mechanical properties can be designed. One remarkable ability of DDNs is their capacity to combine dimensional stability, bond dynamicity, and multi-responsiveness. This review aims to give an overview of the advances in the emerging field of DDNs with a special emphasis on their design, structure-property relationships, and applications. This review illustrates how DDNs offer many prospects that single (dynamic) networks cannot provide and highlights the challenges associated with their synthesis and characterization.

Dissociate transfer exchange of tandem dynamic bonds endows covalent adaptable networks with fast reprocessability and high performance

A covalent adaptable network combining continuous reprocessability and high performance was achieved via dissociate transfer exchange (DTE) of tandem dynamic bonds.

Designing tubular conducting polymer actuators for wireless electropumping

Rational design and shaping of soft smart materials offer potential applications that cannot be addressed with rigid systems. In particular, electroresponsive elastic materials are well-suited for developing original active devices, such as pumps and actuators. However, applying the electric stimulus requires usually a physical connection between the active part and a power supply. Here we report about the design of an electromechanical system based on conducting polymers, enabling the actuation of a wireless microfluidic pump. Using the electric field-induced asymmetric polarization of miniaturized polypyrrole tubes, it is possible to trigger simultaneously site-specific chemical reactions, leading to shrinking and swelling in aqueous solution without any physical connection to a power source. The complementary electrochemical reactions occurring at the opposite extremities of the tube result in a differential change of its diameter. In turn, this electromechanical deformation allows inducing highly controlled fluid dynamics. The performance of such a remotely triggered electrochemically active soft pump can be fine-tuned by optimizing the wall thickness, length and inner diameter of the material. The efficient and fast actuation of the polymer pump opens up new opportunities for actuators in the field of fluidic or microfluidic devices, such as controlled drug release, artificial organs and bioinspired actuators.

Tubular conducting polymer actuators are used for developing a wireless electropumping device. Bipolar electrochemistry, allowing symmetry breaking in terms of polarization and electrochemical reactions, is the key ingredient for efficient pumping.

Effect of Isomeric Amine Chain Extenders and Crosslink Density on the Properties of Liquid Crystal Elastomers

Among the various types of shape changing materials, liquid crystal elastomers (LCEs) have received significant attention as they can undergo programmed and reversible shape transformations. The molecular engineering of LCEs is the key to manipulating their phase transition, mechanical properties, and actuation performance. In this work, LCEs containing three different types of butyl groups (n-, iso-, and sec-butyl) in the side chain were synthesized, and the effect of isomeric amine chain extenders on the thermal, mechanical, and actuation properties of the resulting LCEs was investigated. Because of the considerably low reactivity of the sec-butyl group toward the diacrylate in the LC monomer, only a densely crosslinked LCE was synthesized. Most interestingly, the mechanical properties, actuation temperature, and blocking stress of the LCEs comprising isobutyl groups were higher than those of the LCEs comprising n-butyl groups. This difference was attributed to the presence of branches in the LCEs with isobutyl groups, which resulted in a tighter molecular packing and reduced the free volume. Our results suggest a facile and effective method for synthesizing LCEs with tailored mechanical and actuation properties by the choice of chain extenders, which may advance the development of soft actuators for a variety of applications in aerospace, medicine, and optics.

Liquid Crystal Elastomer Electric Locomotives

In this letter, we present an electro-driven cylindrical actuator system composed of a bilayered liquid crystal elastomer/carbon black (LCE/CB) electro-driven soft actuator and a conductive track. The bilayered LCE/CB electro-driven actuator consists of an inner LCE circular band and several U-shaped CB conductive regions stuck on the outer surface of the LCE ring. Benefiting from the effective Joule heating of CB powder and the consequential inhomogeneous stress generated inside the bilayered LCE/CB film, the cylindrical actuator can roll forward with a rate of 1.6 mm/s along a stationary copper conductive track powered by a 50 V direct current supply. The dynamic connection between the rolling actuator and the conductive track effectively eliminates the limitation of electric wires in the complicated actuation set-ups of the LCE materials. This work might promote the development of electro-driven LCE actuators and have potential applications in the fields of soft robots and electric devices.

Epoxide and oxetane based liquid crystals for advanced functional materials

Liquid crystalline elastomers (LCEs) and liquid crystalline networks (LCNs) are classes of polymers very suitable for fabricating advanced functional materials. Two main pathways to obtain LCEs and LCNs have gained the most attention in the literature, namely the two-step crosslinking of LC side-chain polymers and the photoinitiated free-radical polymerisation of acrylate LC monomers. These liquid crystal polymers have demonstrated remarkable properties resulting from their anisotropic shapes, being used in soft robotics, responsive surfaces and as photonic materials. In this review, we will show that LCs with cyclic ethers as polymerisable groups can be an attractive alternative to the aforementioned reactive acrylate mesogens. These epoxide and oxetane based reactive mesogens could offer a number of advantages over their acrylate-based counterparts, including oxygen insensitivity, reduced polymerisation shrinkage, improved alignment, lower processing viscosity and potentially extended resistivity. In this review, we summarise the research on these materials from the past 30 years and offer a glimpse into the potential of these cyclic ether mesogens.

Liquid crystal elastomer actuator with serpentine locomotion

A snake-mimic soft actuator composed of a bilayered liquid crystal elastomer ribbon and two serrated feet is reported in this work. Under repeated on/off near-infrared light irradiation, this actuator can move forward relying on a reversible shape morphing between S-curve structure and reverse S-curve structure, which is similar to the serpentine locomotion of snakes.

Three-Dimensional Programmable, Reconfigurable, and Recyclable Biomass Soft Actuators Enabled by Designing an Inverse Opal-Mimetic Structure with Exchangeable Interfacial Crosslinks

Despite the unceasing flourishing of intelligent actuators, it still remains a huge challenge to design mechanically robust soft actuators with the characteristics of three-dimensional (3D) programmability, reconfigurability, and recyclability. Here, we utilize fully bioderived natural polymers to fabricate biomass soft actuators (BioSA) integrating all above features through an ingenious microstructure design. BioSA consists of an interconnected inverse opal-mimetic skeleton of sodium alginate (NaAlg) and a continuous matrix of epoxidized natural rubber (ENR), with exchangeable β-hydroxyl ester linkages at their interfaces. The hydrophilic nature and interconnected structure of the NaAlg skeleton endow BioSA with exceedingly acute humidity response and robust mechanical properties. Meanwhile, the dynamic nature of β-hydroxyl ester linkages enables the design of complex 3D structured soft actuators with reconfigurability and recyclability. Since both ENR and NaAlg are derived from natural resources, and the water-based manufacturing process is extremely facile and environmentally friendly, this work provides a novel strategy to fabricate 3D programmable intelligent actuators with both robust mechanical properties and sustainability.

A Review on Liquid Crystal Polymers in Free-Standing Reversible Shape Memory Materials

Liquid crystal polymers have attracted massive attention as stimuli-responsive shape memory materials due to their unique reversible large-scale and high-speed actuations. These materials can be utilized to fabricate artificial muscles, sensors, and actuators driven by thermal order–disorder phase transition or trans–cis photoisomerization. This review collects most commonly used liquid crystal monomers and techniques to macroscopically order and align liquid crystal materials (monodomain), highlighting the unique materials on the thermal and photo responsive reversible shape memory effects. Challenges and potential future applications are also discussed.

Influence of treating parameters on thermomechanical properties of recycled epoxy-acid vitrimers

Vitrimers have the characteristics of shape-reforming and surface-welding, and have the same excellent mechanical properties as thermosets; so vitrimers hold the promise of a broad alternative to traditional plastics. Since their initial introduction in 2011, vitrimers have been applied to many unique applications such as reworkable composites and liquid crystal elastomer actuators. A series of experiments have investigated the effects of reprocessing conditions (such as temperature, time, and pressure) on recycled materials. However, the effect of particle size on the mechanical properties of recycled materials has not been reported. In this paper, we conducted an experimental study on the recovery of epoxy-acid vitrimers of different particle sizes. Epoxy-acid vitrimer powders with different particle size distributions were prepared and characterized. The effects of particle size on the mechanical properties of regenerated epoxy-acid vitrimers were investigated by dynamic mechanical analysis and uniaxial tensile tests. In addition, other processing parameters such as temperature, time, and pressure are discussed, as well as their interaction with particle size. This study helped to refine the vitrimer reprocessing condition parameter toolbox, providing experimental support for the easy and reliable control of the kinetics of the bond exchange reaction.

Liquid-Crystalline Soft Actuators with Switchable Thermal Reprogrammability

Thermal reprogrammability is essential for new-generation large dry soft actuators, but the realization sacrifices the favored actuation performance. The contradiction between thermal reprogrammability and stability hampers efforts to design high-performance soft actuators to be robust and thermally adaptable. Now, a strategy has been developed that relies on repeatedly switching on/off thermal reprogrammability in liquid-crystalline elastomer (LCE) actuators to resolve this problem. By post-synthesis swelling, a latent siloxane exchange reaction can be induced in the common siloxane LCEs (switching on), enabling reprogramming into on-demand 3D-shaped actuators; by switching off the dynamic network by heating, actuation stability is guaranteed even at high temperature (180 °C). Using partially black-ink-patterned LCEs, selectively switching off reprogrammability allows integration of completely different actuation modes in one monolithic actuator for more delicate and elaborate tasks.

Polymer actuators based on covalent adaptable networks

Advances in polymer actuators containing covalent adaptable networks (CANs) are summarized and discussed in this review.

A Focus on Soft Actuation

The present editorial paper analyzes the hundred recent research works on soft actuation to understand the current main research focus in the light of the grand challenges in the field. Two characteristic paper types were obtained: one focuses on soft actuator design, manufacturing and demonstration, while another includes in addition the development of functional materials. Although vast majority of the works showcased soft actuation, evaluation of its robustness by multi-cyclic actuation was reported in less than 50% of the works, while only 10% described successful actuation for more than 1000 cycles. It is suggested that broadening the research focus to include investigation of mechanisms underlying the degradation of soft functional material performance in real cyclic actuation conditions, along with application of artificial intelligence methods for prediction of muscle behavior, may allow overcoming the reliability issues and developing robust soft-material actuators. The outcomes of the present work might be applicable to the entire soft robotics domain.

Harnessing the Day-Night Rhythm of Humidity and Sunlight into Mechanical Work Using Recyclable and Reprogrammable Soft Actuators

Toward a sustainable society, soft actuators driven by environmentally friendly energy from nature are of great social and economic significance. Meanwhile, recyclability, repeated reconfiguration for other use, and complex three-dimensional (3D) geometries are also essential for mitigating the energy crisis and practical application demands. Here, we integrate all of the above features in one actuator using vitrimers with exchangeable disulfide links. By reconfiguration, welding, patterning, and kirigami techniques, complex 3D actuators can be easily fabricated, which can be repeatedly reconfigured for other applications to save cost in new material preparation. These actuators operate synergistically with the day-night rhythm of humidity and sunlight without the need of extra energy input.

Detecting topology freezing transition temperature of vitrimers by AIE luminogens

Vitrimers are one kind of covalently crosslinked polymers that can be reprocessed. Topology freezing transition temperature (Tv) is vitrimer's upper limit temperature for service and lower temperature for recycle. However, there has been no proper method to detect the intrinsic Tv till now. Even worse, current testing methods may lead to a misunderstanding of vitrimers. Here we provide a sensitive and universal method by doping or swelling aggregation-induced-emission (AIE) luminogens into vitrimers. The fluorescence of AIE-luminogens changes dramatically below and over Tv, providing an accurate method to measure Tv without the interference of external force. Moreover, according to this method, Tv is independent of catalyst loading. The opposite idea has been kept for a long time. This method not only is helpful for the practical application of vitrimers so as to reduce white wastes, but also may facilitate deep understanding of vitrimers and further development of functional polymer materials.