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AbstractThe current research highlights regarding future low-dielectric resins for circuit boards lie in their recyclability and pattern ability. In the present work, we put forward a new idea to simultaneously achieve the recyclability and pattern ability of low-dielectric resins in circuit board. In detail, a series of low-dielectric vitrimers were prepared by copolymerization of fluorinated monomers followed by employing imine cross-linked network. By incorporating fluorine-contained units, the dielectric constant of the vitrimers reached to ∼2.4, while preserving high mechanical strength around 33 MPa. Moreover, after reprocessing three times, the dielectric constants of the PFS-imines remained almost unchanged and 89% of original mechanical strength was recovered. Owing to the increased chain relaxation, PFS-imines can be multiply patterned by directly imprinting at the temperature above Tv. Furthermore, the pattern of PFS-imines is removable and reformed, which may be attributed to their reprocessability. Thus, PFS-imine exhibits pattern ability and recyclability, making it particularly suitable for applications in electronic packaging and circuit boards, compared with that of conventional low-dielectric resins. [ABSTRACT FROM AUTHOR]

The development of dynamic covalent materials with repairability, reprocessability, and recyclability is crucial for sustainable development. In this work, we report a new strategy to adjust the thermomechanical properties of boronic ester cross-linked poly(β-hydroxyl amine)s through side-group engineering. By tuning the side groups of the poly(β-hydroxyl amine)s, we have developed self-healable, reprocessable, and shape-programmable materials. By tuning the side groups of the poly(β-hydroxyl amine)s, the thermomechanical properties can be readily adjusted. Notably, the 3-amino-1,2-propanediol-derived polymer exhibits enhanced thermal (Tg = 95 °C) and mechanical (tensile strength = 34.2 MPa) performance due to increased hydrogen bonding. Benefiting from the dynamic reversibility of the boronic esters, these materials demonstrate solvent-assisted healing, reprocessing, chemical recycling, and shape programming capabilities. Given their straightforward synthesis, tunable properties, and robust dynamic features, the boronic ester cross-linked poly(β-hydroxyl amine)s hold great promise for various applications, including flexible electronic and biomedical materials. [ABSTRACT FROM AUTHOR]

Flexible electronics are striving in modern society, and they impose harsh and urgent requirements for flexibility on electronic package substrates. However, traditional materials, including ceramics, metals, or polymers are lack of flexibility. Herein, a polyurethane named PU‐D1Q1VF1 is proposed via incorporating carefully selected biobased units and synergistic dynamic bonds, and the PU‐D1Q1VF1 not only meets the basic requirements of flexibility but also possesses properties of self‐heal, UV‐protection, reprocessability, and degradability. The polycaprolactone diol (PCL diol) was employed as the soft segment, and the bis(2‐hydroxyethyl) disulfide (HEDS) and lignin derived model monomer hydroquinone were selected as chain extenders. Moreover, carefully synthesized bio‐based monomer (E)‐4‐(((furan‐2‐ylmethyl)imino)methyl)‐2‐methoxyphenol (VF) was used as the capping agent, which could facilitate the self‐healing process of the PU‐D1Q1VF1. [ABSTRACT FROM AUTHOR]

A cooperative strategy for simultaneously improving typically conflict properties between mechanical strength and self-healability of elastomers is developed by combining the strong electron-withdrawing and high free-volume effects of fluorine atoms, resulting in the highest recorded puncture energy (648.0 mJ) elastomer so far. [Display omitted] There is usually a trade-off between high mechanical strength and dynamic self-healing because the mechanisms of these properties are mutually exclusive. Herein, we design and fabricate a fluorinated phenolic polyurethane (FPPU) elastomer based on octafluoro-4,4′-biphenol to overcome this challenge. This fluorine-based motif not only tunes interchain interactions through π−π stacking between aromatic rings and free-volume among polymer chains but also improves the reversibility of phenol-carbamate bonds via electron-withdrawing effect of fluorine atoms. The developed FPPU elastomer shows the highest recorded puncture energy (648.0 mJ), high tensile strength (27.0 MPa), as well as excellent self-healing efficiency (92.3%), along with low surface energy (50.9 MJ m−2), notch-insensitivity, and reprocessability compared with non-fluorinated counterpart biphenolic polyurethane (BPPU) elastomer. Taking advantage of the above-mentioned merits of FPPU elastomer, we prepare an anti-fouling triboelectric nanogenerator (TENG) with a self-healable, and reprocessable elastic substrate. Benefiting from stronger electron affinity of fluorine atoms than hydrogen atoms, this electronic device exhibits ultrahigh peak open-circuit voltage of 302.3 V compared to the TENG fabricated from BPPU elastomer. Furthermore, a healable and stretchable conductive composite is prepared. This research provides a distinct and general pathway toward constructing high-performance elastomers and will enable a series of new applications. [ABSTRACT FROM AUTHOR]

The current challenge of recycling rubber articles beyond the failure time has created an increasingly huge burden on the environment. Therefore, there is a growing focus on enhancing the environmental resistance and reprocessability of rubber materials. In this work, we present a simple way to introduce the fluorinated short-side chains on the molecular chains of epoxidized natural rubber (ENR) via the reaction of epoxy groups and carboxyl groups. The results indicated that the short fluorinated side chains endowed ENR the excellent environmental resistance such as thermal stability, thermal oxygen resistance and solvent resistance. At the same time, the cross-linking network formed by the thermally reversible β-hydroxyl ester bonds enables the rubber to a good reprocessability. The second recycled ENR-DTSA-F had achieved 90.4% of the retention ratio of the tensile strength and reached 69.9% of the retention ratio of the elongation at break compared to the original sample. This work provides a simple method for preparing ENR materials with good environmental resistance and reprocessability. [ABSTRACT FROM AUTHOR]

For sustainable application of chloroprene rubber (CR), a new technology is developed by the vulcanization of CR using 2,2'-dithiodipyridine (DPD) as a cross-linking agent with the reprocessing performance owing to disulfide metathesis. When DPD was incorporated into CR vulcanization, the Menschutkin reaction between allyl chloride group and pyridine group occurred with a maximum exothermic peak at 184°C. The number of effective cross-linking bond at 0.5 phr DPD vulcanizate was higher than that at high DPD content. This vulcanizate showed high tensile strength (11.12 MPa) and elongation at break (1253 ± 120%) owing to the exchangeable disulfide bond in the system. Under the catalysis of triphenylphosphine, the metathesis of disulfide compound was improved obviously, which endowed CR/DPD vulcanizates with good recyclability performance. Disulfide cross-linkage maintains its stability at low temperature, thus ensuring the mechanical stability of CR/DPD vulcanizate under the ambient conditions. Vulcanization and reprocessing of CR/DPD vulcanizate can be conducted with common industrial rubber processing equipment. Such reprocessable chloroprene rubber could have potential application in CR industry, also serve to significantly improve environmental sustainability. [ABSTRACT FROM AUTHOR]

To address the issues that waste of resources and environmental pollution caused by discarded materials, dynamic bonds are widely introduced into polymers to endow them with reprocess ability. However, there are some obvious issues in existing research such as poor toughness, low fracture elongation, and inability for repeated reprocessing of materials. Considering above problems, this study introduces dense hydrogen bonding and cation–π interactions into the polyurea system, and develops a high‐performance transparent film based on dual dynamic non‐covalent interactions, which enables the film to be reprocessed. Through the synergy of the dual non‐covalent networks, the film exhibits a high tensile strength of 79.6 ± 3.9 MPa and good hardness (pencil hardness of 4H, elastic modulus of 2.69 GPa). It can effectively resist the scratching of copper brush and maintain more than 97% of its initial mechanical strength after being reprocessed five times. In addition, the film has good adhesion to various substrates, as well as high flexibility (0.5 mm) and excellent optical properties (high light transmission of 91.1% and low haze of 0.94%). This study proposes a novel approach to enable polymer materials to be reprocessed and demonstrates the preparation of a film with great potential in optical protection and wearable devices. [ABSTRACT FROM AUTHOR]

The development of soft photoactuators with multifunctionality and improved performance is highly important for their broad applications. Herein, we report on a facile and efficient strategy for fabricating such photoactuators with UV‐NIR dual light‐responsivity, room‐temperature 3D shape reprogrammability and reprocessability, and photothermal healability by doping polydopamine (PDA) nanoparticles into a main‐chain azobenzene semi‐crystalline poly(ester‐amide) (PEA). The PEA/PDA nanoparticle composite was readily processed into free‐standing films with enhanced mechanical and photomechanical properties compared with the blank PEA films. Its physically crosslinked uniaxially oriented films showed rapid and highly reversible photochemically induced bending/unbending under the UV/visible light irradiation at room temperature in both the air atmosphere and water. When exposed to the NIR light, they (and their bilayer films formed with a polyimide film) exhibited photothermally induced bending even at a temperature much lower than their crystalline‐to‐isotropic phase transition temperature based on a unique mechanism (involving photothermally induced polymer chain relaxation due to the disruption of their hydrogen bonds). The room‐temperature 3D shape reprogrammability and reprocessability and photothermal healability of the composite polymer films were also demonstrated. Such multifunctional dual light‐responsive photoactuators with well‐balanced mechanical robustness, actuation stability, 3D shape reprogrammability/reprocessability and photothermal healability hold much promise in various photoactuating applications. [ABSTRACT FROM AUTHOR]

Designing sustainable materials with tunable mechanical properties, intrinsic degradability, and recyclability from renewable biomass through a mild process has become vital in polymer science. Traditional phenolic resins are generally considered to be not degradable or recyclable. Here we report the design and synthesis of linear and network structured phenolic polymers using facile polycondensation between natural aldehyde‐bearing phenolic compounds and polymercaptans. Linear phenolic products are amorphous with Tg between −9 °C and 12 °C. Cross‐linked networks from vanillin and its di‐aldehyde derivative exhibited excellent mechanical strength between 6–64 MPa. The connecting dithioacetals are associatively adaptable strong bonds and susceptible to degradation in oxidative conditions to regenerate vanillin. These results highlight the potential of biobased sustainable phenolic polymers with recyclability and selective degradation, as a complement to the traditional phenol‐formaldehyde resins. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are of great concern in many fields. However, they suffer from high toxicity and may lead to environmental pollution. We report the development of a QD‐vitrimer composite with reprocessable, self‐healable, and sustainable properties. Our QD‐vitrimer composite reveals fine transparency and highly uniform QDs distribution without significant aggregation. The photoluminescence quantum yield (PLQY) is basically about four times higher than the commercial QD films. The QD‐vitrimer composites can be recycled at least three times without any significant loss in structure and luminescence efficiency. A prototype light‐emitting diode device is fabricated to demonstrate the promising potential of QD‐vitrimer composites in real application. This research sheds light on developing environmentally friendly luminescent materials and opens up an avenue for designing advanced nanomaterials‐vitrimer composites. [ABSTRACT FROM AUTHOR]

To minimize the environmental pollution caused by polymeric waste, materials based dynamic chemistry have attracted extensive attention around the world. Various dynamic covalent bonds or noncovalent interactions have been employed to design multifunctional polymers with recyclability, reprocessablility, and sustainability. Among them, polymers based on reversible boron–oxygen (B–O) bonds have been widely investigated because of their unique properties. Particularly, lots of scientists have demonstrated that the combination with boron–nitrogen (B–N) coordination can effectively accelerate the dynamicity as well as enhance the stability of B–O bonds. Therefore, numerous polymers containing dynamic B–O bonds with dative B–N coordination have been designed and synthesized in recent years. These polymers exhibit excellent versatility and great potential for diverse applications such as biosensors, battery electrolytes, and artificial skins. This review provides an overview of the comprehensive influence of dynamic B–N coordination chemistry on B–O bonds in organoboron species and highlights the developments in the area of constructing boron‐containing polymeric materials with this interesting linkage. The design guidelines, existing challenges, and future perspectives in this burgeoning field are discussed and proposed. [ABSTRACT FROM AUTHOR]

Abstract To minimize the environmental pollution caused by polymeric waste, materials based dynamic chemistry have attracted extensive attention around the world. Various dynamic covalent bonds or noncovalent interactions have been employed to design multifunctional polymers with recyclability, reprocessablility, and sustainability. Among them, polymers based on reversible boron–oxygen (B–O) bonds have been widely investigated because of their unique properties. Particularly, lots of scientists have demonstrated that the combination with boron–nitrogen (B–N) coordination can effectively accelerate the dynamicity as well as enhance the stability of B–O bonds. Therefore, numerous polymers containing dynamic B–O bonds with dative B–N coordination have been designed and synthesized in recent years. These polymers exhibit excellent versatility and great potential for diverse applications such as biosensors, battery electrolytes, and artificial skins. This review provides an overview of the comprehensive influence of dynamic B–N coordination chemistry on B–O bonds in organoboron species and highlights the developments in the area of constructing boron‐containing polymeric materials with this interesting linkage. The design guidelines, existing challenges, and future perspectives in this burgeoning field are discussed and proposed.

Thermosetting materials have limitations in terms of reshaping and recycling due to their irreversible bond structures, leading to significant plastic waste issues. Recently, epoxy vitrimers based on dynamic covalent bond exchange have been introduced as promising alternatives to traditional thermosets. Particularly, they demonstrate significant potential applications in the field of multi-responsive materials. In this research, a self-healable and mechano-responsive vitrimer (EB-V) is successfully prepared, incorporating epoxide spiropyran beads (ESP beads) derived from citric acid and epoxy derivatives. To enable self-reporting of cracks through color changes, ESP beads are covalently bonded to the vitrimer via an epoxy-carboxylic acid reaction. The photochromic properties of EB-V are demonstrated by color and fluorescence changes, and its tensile strength increased from 2.0 to 6.8 MPa compared to the control sample. Dynamic mechanical analysis confirmed the covalent exchange reaction of the vitrimer, revealing its reconfigurable behavior and stress relaxation at elevated temperatures. Furthermore, EB-V exhibited exceptional properties, including self-healing and reprocessability. As a smart material, it holds great promise for a wide range of applications, such as sensors, actuators, 4D printing, and industrial safety diagnostics., (© 2024 Wiley‐VCH GmbH.)

Dynamic bond chemistry provides a new opportunity for the reprocess and reuse of low-dielectric resins. In this study, based on our previous study, a series of reprocessable low-dielectric styrene resins were prepared by incorporating coordinated crosslinked structures with Cu, Zn, and Ni centers. The low-dielectric properties, mechanical strength, and reprocessing performance of styrene resins were significantly affected by the metal centers. Styrene resins with Cu and Ni centers (PSVP-Cu and PSVP-Ni, respectively) possessed high mechanical strength and low dielectric constant than that styrene resin with Zn center (PSVP-Zn). Further investigation indicated that PSVP-Cu and PSVP-Ni had relatively high cross-linking densities, possibly owing to the relatively high bonding energies of Cu-pyridine and Ni-pyridine. After the 3rd cycle, PSVP-Ni preserved its high mechanical strength and low dielectric constant, thereby exhibiting good recyclability for potential applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The multicomponent polymerization of diamines, CS 2 , and diacrylates. • The synthesized polydithiourethanes could be efficiently degraded via aminolysis. • The prepared polydithiourethanes networks could be reprocessed. In the pursuit of advanced functional polymer materials, sulfur-containing polymers have received tremendous attention owing to their superior chemical stability, high refractive indices, various supramolecular interactions, and robust dynamic covalent chemistry. However, their synthesis usually involves either expensive monomers or toxic byproducts and requires catalysts, thus hindering their widespread application. In this work, we present a catalyst-free multicomponent polymerization in organic solvents for the synthesis of various polydithiourethanes with excellent yields (up to 98 %) and high molecular weights (up to 112 kg/mol). This reaction involves the direct polymerization of carbon disulfide, an abundant one-carbon feedstock, with commercially available diamines and diacrylates. This polyaddition process demonstrates high atom economy and no byproduct, occurring at room temperature without the need for a catalyst, thus exhibiting excellent green chemistry metrics. By utilizing the dynamic covalent chemistry of dithiourethane groups, these polymers can be efficiently degraded via aminolysis and used to fabricate reprocessable vitrimers. This multicomponent polymerization opens up a new avenue for the efficient utilization of carbon disulfide resources and accelerates the exploration of diversified sulfur-containing functional polymer materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dimer acid (DA) prepolyamides (DAPAcs) were synthesized from a diamine and excess DA. • Crosslinked polyβ-hydroxyesters (cPHEs) were prepared from biobased raw materials. • cPHEs were prepared through a ROP polymerization of DAPAcs and a dicyclocarbonate. • The reaction between HOOC– and cyclocarbonate groups forms β-hydroxyester units. • The β-hydroxylester units provided good reprocessability of cPHEs. A new kind of biobased partially crosslinked polyβ-hydroxyesters (cPHEs) was synthesized through the ring-opening polymerization of a five-membered dicyclocarbonate and carboxyl-terminated dimer acid (DA) oligopolyamides (DAPAcs). The DAPAcs provided carboxyl groups and attacked the cyclocarbonate groups to form β-hydroxyester units, which was confirmed by a model reaction. DAPAcs were synthesized from hexamethylenediamine and excess DA. Their structure and properties were confirmed by FTIR, 1H NMR, and DSC. cPHEs exhibited semicrystalline characters with good thermal properties evidenced by wide-angle X-ray scattering, DSC, and TGA. Introducing DAPA sequences improved intermolecular interactions and tensile strength. The attack of pendent hydroxy groups to remaining cyclocarbonate groups led to crosslinked cPHEs. Dynamic β-hydroxylester segments impart the reprocessability of cPHEs, and stress relaxation experiments were conducted at different temperatures to evaluate the exchange kinetics. A new synthetic route different from normal epoxy-carboxyl route was established. This method broadens the research of polyβ-hydroxylesters and their application range. [ABSTRACT FROM AUTHOR]

In the present work a recyclable and reprocessable vitrimer suitable for pultrusion process has been formulated and a pultruded profile reshaped by thermoforming has been manufactured therefrom. A DGEBA epoxy resin with medium range viscosity and a bis(a-aminophenyl disulfide) as dynamic crosslinker were used for the synthesis of the vitrimer. The thermal stability was studied by thermogravimetric analysis (TGA) and curing behaviour and curing kinetics were studied by means of dynamic scanning calorimeter (DSC) and rheology measurements. Mechanical properties of the dynamic resins and its counterpart epoxy resin and of the fabricated carbon fibre reinforced polymers (CFRP) were determined. The dynamic resin showed a fast stress relaxation at temperatures above 150 °C. Finally, as a proof of concept, mechanical recyclability and the thermoforming of the vitrimer-based pultruded profile have been validated.

Photoactuators are promising smart materials that can adapt their shapes upon light illumination. Smart materials with recycling, reusable, and reconfigurable properties are crucial for a sustainable society, and it is important to expand their function. Recently, much effort was made to address the issue of reprocessability and recyclability of photoactuators. Based on the development of polymer chemistry, supramolecular chemistry, and dynamic covalent chemistry, it is now possible to prepare reconfigurable and recyclable photoactuators using azobenzene-containing polymers (azopolymers). Herein, the recent advances on reconfigurable and reprocessable photoactuators, including dynamic crosslinked networks systems and non-covalently crosslinked azobenzene-containing polymers, were reviewed. We discuss the challenges in the field as well as the directions for the development of such photoactuators.

Ionic conductive elastomers (ICEs) exhibit a compelling combination of ionic conductivity and elastic properties, rendering them excellent candidates for stretchable electronics, particularly in applications like sensing devices. Despite their appeal, a significant challenge lies in the reprocessing of ICEs without compromising their performance. To address this issue, we propose a strategy that leverages covalent adaptable networks (CANs) for the preparation of ICEs. Specifically, β-amino ester bonds as dynamic motifs are incorporated into a poly(ethylene oxide) network containing lithium bis(trifluoromethane) sulfonimide (LiTFSI) salt. LiTFSI-containing β-amino ester networks (LBAEs) exhibit superb transparency (94%), thermal stability (>280 °C), and modest conductivity (0.00576 mS·cm -1 at 20 °C), and some LBAEs maintain operational capability across a wide temperature range (-20 to 100 °C). By regulating the lithium salt content, the mechanical properties, conductivities, and viscoelastic behaviors can be tailored. Benefiting from these features, LBAEs have been successfully applied in sensing devices for monitoring human motion (e.g., finger bending, swallowing, and clenching). Notably, even after four reprocessing cycles, LBAEs demonstrate structural integrity and maintain their operational capability. This novel approach represents a promising solution to the reprocessing challenges associated with flexible conductive devices, demonstrating the successful integration of CANs and ICEs.

Polymers are playing important roles in the rapid development of triboelectric nanogenerators (TENGs); However, most polymers cannot meet the high requirements of thermomechanical performance; Thus, various polymeric composites are developed for triboelectric layer. These composites are hardly recycled since their reinforcements are unevenly distributed after reprocessing, which limits the sustainable development of TENGs. To solve the above challenges, in situ generated nanofiber reinforced composites (NFRCs) based on single-component liquid crystal polyarylate (LCP) are designed and prepared via a one-step polycondensation. Nonlinear naphthalene (NDA) widens the processing window of LCP without destabilizing the liquid crystal phase. The NDA-rich domains act as a matrix while the NDA-poor domains with higher rigidity form oriented nanofibers to achieve self-reinforcement. The resultant NFRCs possess high glass transition temperature (T g > 220 °C) and storage modulus (E' = 0.1 GPa at 350 °C), which are far beyond existing triboelectric polymers, typically T g < 110 °C and E' < 0.1 MPa (flowable) at 350 °C. Furthermore, NFRC-based TENG exhibits superior electrical output performance and retention rate (>90%) after reprocessing; Overall, this work offers a new design principle to prepare self-reinforced composites, which paves a way to explore high performance materials., (© 2024 Wiley‐VCH GmbH.)

Photodeformable azobenzene (azo) polymers are a class of smart polymers that can efficiently convert light energy into mechanical power, holding great promise in various photoactuating applications. They are typically of crosslinked polymer networks with highly oriented azo mesogens embedded inside. Upon exposure to the light of appropriate wavelength, they experience dramatic order parameter change following the configuration change of the azo units. This could result in the generation and accumulation of the gradient microscopic photomechanical force in the crosslinked polymer networks, thus leading to their macroscopic deformation. So far, a great number of photodeformable azo polymers have been developed, including some unoriented ones showing photodeformation based on different mechanisms. Among them, photodeformable azo polymers with dynamic crosslinking networks (and some uncrosslinked ones) have aroused particular interest recently because of their obvious advantages over those with stable chemical crosslinking structures such as high recyclability and reprocessability. In this paper, I provide a detailed overview of the recent progress in such reprocessable photodeformable polymers. In addition, some challenges and perspectives are also presented.

Reprocessable and degradable lignin-derived epoxy vitrimers were prepared via imine chemistry. • Acid degradable epoxy vitrimers with imine bonds were synthesized from vanillin. • The self-healing ability was achieved without using catalysts or expensive hardener. • The mechanical properties were at the same level of E51 epoxy thermosets. • The mechanical properties of vitrimers were not deteriorated after three recycles. The preparation of vanillin-based epoxy thermosets has attracted great attention in recent years, however, most of them could not be reprocessed once after curing procedures. In the present work, a vanillin-based epoxy vitrimer (Van-Ep/IPDA) with dynamic imine covalent bonds was prepared by curing mono-glycidyl structure of vanillin (Van-Ep) with isophorone diamine (IPDA) hardener, which simultaneously exhibits the excellent reprocessability and acid degradable behavior. The mechanical properties of Van-Ep/IPDA vitrimers and cured bisphenol A (E51) epoxy are kept at the same level, which the Young's modulus, elongation and tensile strength at break of Van-Ep/IPDA vitrimers reach 2.30 GPa, 4.4% and 65.0 MPa, respectively. Importantly, compared with these of original vitrimers, all reprocessed Van-Ep/IPDA vitrimers exhibit the same level of mechanical properties even after three times of hot pressing. Thanks to the imine structure, epoxy vitrimers also exhibit degradable property under acid solution. This facile approach of imine chemistry for preparing vanillin-based epoxy vitrimers sets up an important framework for designing sustainable polymer materials with excellent reprocessability and degradability. [ABSTRACT FROM AUTHOR]

In this work, a bio-based reprocessable and degradable polybenzoxazine with acetal structures was designed and prepared. A diphenol containing acetal structures (DVEA) was reacted with stearylamine and paraformaldehyde to obtain a benzoxazine monomer (DVEA-s). The curing behavior of DVEA-s was investigated using differential scanning calorimetry and in-situ Fourier transform infrared spectroscopy, and the curing kinetics of DVEA-s were also studied. Due to the thermal exchange of acetal structures, the obtained polybenzoxazine (PDVEA-s) exhibited quick stress relaxation. Mechanically crushed PDVEA-s could be reprocessed by hot-pressing at 120 °C for 10 min. Furthermore, the degradation properties of PDVEA-s under different conditions were studied. The results showed that PDVEA-s could be completely degraded in acidic tetrahydrofuran aqueous solution at 50 °C in 4 min. [Display omitted] • A novel bio-based benzoxazine (DVEA-s) with acetal structures was synthesized. • The polybenzoxazine (PDVEA-s) can be degraded completely within 4 min. • Mechanically crushed PDVEA-s can be reprocessed by hot-pressing. [ABSTRACT FROM AUTHOR]

In their Research Article (e202305677), Shichao Xu, Liang Yuan et al. found several catalysts for making linear and network-structured phenolic polymers from plant-derived monomers. Keywords: Degradable; Polydithioacetals; Reprocessable; Sustainable Polymers; Vanillin EN Degradable Polydithioacetals Reprocessable Sustainable Polymers Vanillin 1 1 1 08/31/23 20230904 NES 230904 B A thiol-aldehyde polycondensation b was developed for the polymerization of phenolic compounds. Degradable, Polydithioacetals, Reprocessable, Sustainable Polymers, Vanillin. [Extracted from the article]

In their Research Article (e202305677), Shichao Xu, Liang Yuan et al. found several catalysts for making linear and network-structured phenolic polymers from plant-derived monomers. Degradable, Polydithioacetals, Reprocessable, Sustainable Polymers, Vanillin Keywords: Degradable; Polydithioacetals; Reprocessable; Sustainable Polymers; Vanillin EN Degradable Polydithioacetals Reprocessable Sustainable Polymers Vanillin 1 1 1 09/01/23 20230904 NES 230904 B A thiol-aldehyde polycondensation b was developed for the polymerization of phenolic compounds. [Extracted from the article]

ABSTRACT The research activities in the development of recyclable and reprocessable covalently crosslinked networks, and the construction of polymers from renewable resources are both stemmed from the economical and environmental problems associated with traditional thermosets. However, there is little effort in combination of these two attractive strategies in material designs. This article reported a bio-based vitrimer constructed from isosorbide-derived epoxy and aromatic diamines containing disulfide bonds. The resulted dynamic epoxy resins showed comparable thermomechanical properties as compared to similar epoxy networks cured by traditional curing agent. Rheological tests demonstrated the fast stress relaxation of the dynamic network due to the rapid metathesis of disulfide bonds at temperature higher than glass transition temperature. This feature permitted the recycling and reprocessing of the fragmented samples for several times by hot press. The dynamic epoxy resins also exhibited shape-memory effect, and it is demonstrated that the shape recovery ratio could be readily adjusted by controlling the stress relaxation in the temporary state at programming temperature. Moreover, the degradability of the dynamic epoxy resins in alkaline aqueous solution was also demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1790-1799 [ABSTRACT FROM AUTHOR]

Cover Feature: Quantum Dot-Vitrimer Composites: An Approach for Reprocessable, Self-Healable, and Sustainable Luminescent Materials (ChemSusChem 13/2023) Vitrimer, quantum dots, light-emitting diode, self-healing, reprocessable Keywords: vitrimer; quantum dots; light-emitting diode; self-healing; reprocessable EN vitrimer quantum dots light-emitting diode self-healing reprocessable 1 1 1 07/11/23 20230707 NES 230707 B The Cover Feature b shows a novel quantum dots-vitrimer composite. [Extracted from the article]

It is challenging and attractive to prepare the bio-based polymers with comparable or even improved properties in terms of sustainability and economics. Here, the cellulose-based polyurethane films with ethyl cellulose as a soft segment to fully substitute polyether polyols were prepared in a facile and environmentally friendly preparation process. Moreover, the selected sample exhibited high transparency (transmittance of 84.4%), good shape memory behavior (shape fixation ratio of 95% and shape recovery ratio of 94.4%), tensile strength (9.2 MPa), good biodegradability (degradation half-life (t 1/2) of 38 d) and excellent reprocessability (recycled 10 times). Especially, the cellulose-based polyurethane films performed the role of adhesive bonding with the different substrates. In addition, by adding Al 2 O 3 nanoparticles, the EC-PU composites not only exhibited high transparency and excellent adhesive strength but also improved thermal conductivity. At a low filler loading (2.5 wt%) of Al 2 O 3 nanoparticles (30 nm), the Al 2 O 3 -EC-PU4 film not only maintained higher transmittance of 73.6% but also had excellent lap-shear strength of 3.04 MPa. Moreover, both the thermal conductivity and thermal diffusivity of Al 2 O 3 -EC-PU4 film reached as high as 0.92 W/mK and 14.81 mm2/s, which are 146% and 1048% higher than the blank sample. Therefore, it has great potential in developing high performance bio-based plastics and transparent electronic fields. [ABSTRACT FROM AUTHOR]

• Integration of multi-dimensional mechanical properties. • Bridging the contradiction between self-repairing and mechanical properties. • Outstanding elasticity contributes to the development of flexible sensors. • Reprocessability of Thermosetting Polymers. • Excellent optical properties and durability. Achieving robust, high elasticity, transparency, self-repairing, reprocessability and durability simultaneously remains a huge challenge. In this work, we propose a simple strategy to prepare an ultra-high strength, outstanding elasticity, self-repairing and reprocessable poly (thiourethane-urea) (PTUU) film based on interlocking hydrogen bonds (IHBs) and reversible topological networks. The IHBs between its main chains make it have ultra-high tensile strength (61.6 MPa) and good scratch resistance. It is the highest tensile strength ever recorded for crosslinked self-repairing materials at medium temperature thus far. The synergistic effect of IHBs and topological networks makes it high elasticity and can repair more than 90 % of the mechanical strength. Rearrangement of reversible topology network at high temperature endows PTUU with reprocessability, and the mechanical strength remains more than 85 % after reprocessing for three times. In addition, PTUU films have high transmittance (96.6 %, 0.5 mm), low haze, high refractive index and excellent durability, which have broad application prospects in transparent protective materials, optical lenses, stretchable fibers, wearable electronic devices and other fields. [ABSTRACT FROM AUTHOR]

Nowadays, biomass-derived monomers production and thermosets' recyclability are the two main efforts in the development of sustainable thermosetting epoxy resins to replace fossil derivatives and mitigate landfill build-up and ecological impact. Here, we propose a simple step and benign synthesis strategy by using the itaconic acid (IA) and two epoxidized vegetable oils (EVOs), linseed and soybean, in order to obtain fully bio-based materials with high carbon bio-content. The reactivity of these formulations, together with the properties of obtained thermosets were investigated and compared with that of DGEBA/IA homologous system. The EVOs/IA reactive mixtures show high reactivity, tested by differential scanning calorimetry (DSC) and Fourier-transformed infrared spectroscopy (FT-IR) while the obtained resins display good mechanical properties, high thermal stability as well as resistance to solvents. Due to the transesterification reaction in the polyester-based networks, recycling abilities tested both mechanically and chemically were proven. The fully reprocessed bio-based thermosets displayed almost unchanged thermomechanical properties and chemical structure combined with a simple and green chemical processing. • Benign processing of epoxidized vegetable oils formulated with itaconic acid. • Fully biobased epoxy thermosets with reprocessable properties. • High thermal, solvent stability and gel content. • A bio-based carbon content and carbon bio-content from 80% to 96.4%. [ABSTRACT FROM AUTHOR]

Shape reconfigurable devices, e.g., foldable phones, have emerged with the development of flexible electronics. But their rigid frames limit the feasible shapes for the devices. To achieve freely changeable shapes yet keep the rigidity of devices for user-friendly operations, stiffness-tunable materials are desired, especially under electrical control. However, current such systems are multilayer with at least a heater layer and a structural layer, leading to complex fabrication, high cost, and loss of reprocessability. Herein, we fabricate covalent adaptable networks-carbon nanotubes (CAN-CNT) composites to realize Joule heating controlled stiffness. The nanocomposites function as stiffness-tunable matrices, electric heaters, and softening sensors all by themselves. The self-reporting of softening is used to regulate the power control, and the sensing mechanism is investigated by simulating the CNT-polymer chain interactions at the nanoscale during the softening process. The nanocomposites not only have adjustable mechanical and thermodynamic properties but also are easy to fabricate at low cost and exhibit reprocessability and recyclability benefiting from the dynamic exchange reactions of CANs. Shape and stiffness control of flexible display systems are demonstrated with the nanocomposites as framing material, where freely reconfigurable shapes are realized to achieve convenient operation, wearing, or storage, fully exploiting their flexible potential.

Azobenzene (azo) polymer photoactuators with full room-temperature reprogrammability, reprocessability, and photomobility are highly desirable for large-scale applications, but their development remains a daunting challenge. Herein, a strategy is first presented for fabricating such advanced photoactuators from a high-molecular-weight main-chain azo crystalline poly(ester-amide) (PEA) prepared via Michael addition polymerization. This azo PEA can be readily processed into both physically cross-linked, uniaxially oriented fibers and films with high mechanical robustness and reversible photoinduced bending/unbending at room temperature. Importantly, the presence of both amide unit-induced hydrogen bonding and crystalline domains in such films and fibers endows them with dynamic, yet stable cross-linking points, which enable their easy reprogrammability under strain at room temperature into various three-dimensional (3D) shapes (e.g., film helicoid and spiral ribbon, fiber spring) capable of showing completely different shape-dependent photomobile modes. In particular, these reshaped photoactuators can maintain their accurate 3D shapes and highly reversible photoinduced motions even after being kept at 80 °C for 20 days or at 100 °C for 2 days. They can also be reprocessed and recycled from solution at room temperature. Such a multifunctional main-chain azo crystalline PEA can serve as a versatile platform for fabricating various photoactuators with desired 3D shapes and motion modes under mild ambient conditions.

Photodeformable azobenzene (azo) polymers are a class of smart polymers that can efficiently convert light energy into mechanical power, holding great promise in various photoactuating applications. They are typically of crosslinked polymer networks with highly oriented azo mesogens embedded inside. Upon exposure to the light of appropriate wavelength, they experience dramatic order parameter change following the configuration change of the azo units. This could result in the generation and accumulation of the gradient microscopic photomechanical force in the crosslinked polymer networks, thus leading to their macroscopic deformation. So far, a great number of photodeformable azo polymers have been developed, including some unoriented ones showing photodeformation based on different mechanisms. Among them, photodeformable azo polymers with dynamic crosslinking networks (and some uncrosslinked ones) have aroused particular interest recently because of their obvious advantages over those with stable chemical crosslinking structures such as high recyclability and reprocessability. In this paper, I provide a detailed overview of the recent progress in such reprocessable photodeformable polymers. In addition, some challenges and perspectives are also presented. [ABSTRACT FROM AUTHOR]

From cars to airplanes, from household appliances to indoor ornaments, from biomedical devices to factory equipment, epoxy resins have been deeply rooted in modern society. But at the same time, they also bring about a lot of wastes after use due to their insoluble and infusible nature. Vitrimer opens up great opportunities towards to a sustainable society by producing reprocessable epoxies and even thermosets. Epoxy vitrimers are not only the first reported vitrimers, but also the most studied vitrimers. Epoxy vitrimers are reversible covalently crosslinked networks with dynamic covalent bonds, combining excellent mechanic properties of thermosets with reprocessability of thermoplastics. Moreover, the exchangeable network endows vitrimers with excellent reprocessing, self-healing, welding, reshaping and recycling properties. So vitrimers are hopeful to replace traditional thermosets for a wide range of applications in aerospace materials, electronic devices, consumer products of daily life and so on. This review summarizes recent advances in epoxy vitrimer research. The classification and fabrication of epoxy vitrimers and their composites are thoroughly discussed. New properties of epoxy vitrimers brought by the dynamic covalent bonds are also reviewed in-depth. Their potential applications are subsequently explored and summarized. [ABSTRACT FROM AUTHOR]

In this letter, we present a robust covalent adaptable network (CAN) that relies on dynamic, exchangeable thiourethanes. A primary aliphatic isocyanate, hexamethylene diisocyanate (HDI), and a primary aliphatic thiol, ethoxylated-trimethylolpropane tri(3-mercaptopropionate) (EETMP), are employed to form a network that can fully relieve an applied stress at 90 °C in under 40 min through the thiourethane bond exchange with a low loading (1 mol%) of catalyst, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN). Based on the kinetic behavior of the dynamic chemistry, and as monitored via real-time FT-IR, synergetic dissociation and association mechanisms of the thiourethane bond exchange are proposed to explain the higher catalyst efficiency of the combined basic and nucleophilic catalyst, DBN, as compared to the strong basic catalyst, potassium tert-butoxide, and the strong nucleophilic catalyst, N-hetero carbene. Moreover, this thiourethane network exhibits excellent reprocessablity under relatively mild conditions (110 °C), which makes it a promising potential alternative to urethane materials in industry. Image 1 • Thiourehane, Reprocessable, Dynamic Network, Thermoset, Exchangeable. [ABSTRACT FROM AUTHOR]

Reprocessable acrylate vitrimer needs to enhance its strength to expand the application in photo-three-dimensional (photo-3D) printing. However, the methods for improving mechanical properties by the addition of nanofillers or a multifunctional resin into acrylate vitrimers are inappropriate for photo-3D printing due to the low curing speed of photopolymerization induced by weakening light transmittance or reduction of dimensional accuracy caused by large shrinkage. At present, we demonstrate a new strategy for developing a kind of mechanically robust and reprocessable 3D printing thermosets by combining hydrogen bonds and exchangeable β-hydroxyl esters into acrylate vitrimers. To realize this purpose, diacrylate prepolymer containing β-hydroxyl esters was first synthesized from glycidyl methacrylate and suberic acid. Then, the resin formulations for 3D printing comprising the synthesized diacrylate prepolymer together with acrylamide generate exchanged β-hydroxyl ester and pendent amide in cross-linked networks. Here, hydrogen bonds resulting from the amide group as sacrificial bonds dissipate vast mechanical energy under an external load. With the inclusion of 20 wt % acrylamide, the average tensile strength and Young's modulus are up to 40.1 and 871 MPa, which increased by about 4.4 and 3.85 times, respectively. The network rearrangement of cross-linked vitrimers can be achieved through the dynamic ester exchange reactions with gradual disappearance of hydrogen bonds at elevated temperatures, imparting reprocessability into the printed structures. Various photo-3D printing or UV irradiation shapes were successfully produced, and these dissolved in ethylene glycol could be remolded again.