Dynamic covalent chemistry enables temperature-stimulated recycling and self-healing properties of polymeric materials (1). Specifically, the Furan/Maleimide Diels-Alder (FMDA) reaction offers a wide range of Diels-Alder (TDA) and retro-Diels-Alder (TrDA) reaction temperatures, depending on the nature of the substituents (2,3) enabling the design of a variety of temperature-sensitive polymeric systems. This study proposes to systematically investigate the impact of furan substituent on TDA and TrDA of exo and endo adducts from their reaction with the commercially available 1,1′-(methylenedi-4,1-phenylene)bismaleimide (BMI) through 1H-NMR monitoring. The nature of the chemical groups beared by the furan substituent (esters, ether, amide or sulfide bridge), their number and position were also studied to determine the thermal stability of each FMDA adducts.
As an example, 2-furfuryl acetate (FOM) having an electron-donating effect exhibits a completely different reactivity from methyl 2-furoate (FAM). At 30 °C, FOM reached 80 % conversion rate after 24 h while FAM only reached 30 % after 14 days. Moreover, two distinct TrDA were measured for the FOM-based adducts. The TrDA-Endo was around 40 °C and allowed the formation of the more stable Exo-adduct, for which a TrDA-Exo was measured at 90 °C.
This approach was then applied to more sterically hindered systems, in order to simulate the FMDA reaction of functional polycondensates, with the objective to identify the best structures to be used in the development of reversible polymer networks.

Polylactide (PLA) is a biocompatible, biodegradable polymer obtained from renewable resources and used in different applications. To improve PLA thermal properties and introduce shape stability, the multifunctional hydroxyl-terminated PLA could be coupled by diisocyanate and the poly(ester-urethane) network is formed. The disadvantage of such networks is that they cannot be reshaped or reprocessed. To address this issue, the concept of ‘dynamic polymer networks’ can be applied [1], where the networks can rearrange their structure due to the presence of linkages that undergo exchange reactions when exposed to appropriate stimuli.
In this study poly(ester-urethane) networks incorporating an additional low molecular weight diol with weak covalent bonds susceptible to thermal dissociation were investigated. The tetraphenylethane group was employed as an additional diol, capable of reversible dissociation. Analogous networks with permanent bonds were synthesised for comparison. Thermal, mechanical, and rheological properties of obtained networks with varying reversible bond densities were analysed along with their reprocessing ability. Some samples containing dynamic bonds were suitable candidates for reprocessing with the 3D printing technique [2].

Acknowledgements:
The study was performed within Grants NCN 2018/31/B/ST8/01969, DKRVO (RP/CPS/2024-28/003), VEGA 2/0153/25.

For many years, polymers were built exclusively from strong bonds. Nowadays, inspired by nature, scientists have realized the significance of weak sacrificial bonds, which are reversible and introduce dynamic behaviors into otherwise rigid systems. Incorporating such bonds into polymeric materials can provide them appealing properties such as self-healing, stimuli responsiveness, or higher toughness, but have also drawbacks including lower mechanical strength, or bad shape persistence. [1,2] One alternative to avoid these limitations could be to embed the sacrificial bonds in a macrocycle acting as a tether, so that the parts of the bond would remain connected after breaking. [3] Before applying this concept to materials, it is important to understand the changes induced by this embedding on the sacrificial bond characteristics. Single-molecule force spectroscopy (SMFS) represents an ideal technique to study such properties, providing detailed information about bond breaking and even reformation. [4,5] In this work, we present the development of polymer chains containing sacrificial bonds embedded in macrocycle tethers, suitable for SFMS experiments. The synthesis of tethered macrocycles containing two types of sacrificial bonds, disulfide (-S-S-) and azo (-N=N-), is described first. Polymer chains are then grown on each side of these tethered structures by SET-LRP, made of a first flexible poly(methyl acrylate) block, and a "sticky" poly(glycidyl acrylate) block for adhesion on the substrate and on the AFM cantilever. Preliminary SMFS experiments were conducted on these polymers to understand how they respond to force and probe the signature of the sacrificial bond breaking.

In recent decades, polymer research has focused on developing self-healing materials that work efficiently without external stimuli for a broad range of applications. The introduction of hydrogen bonding units within such materials can promote their self-healing behavior with opportunities for its further refinement due the long-range arrangement of hydrogen bonds. Herein, we examine the impact of introducing 1,2-disubstituted cyclohexyl thioureas (TUCyH) into ethylene glycol polymers to understand the impact of chirality on their properties, in particular their self-healing. We find that their introduction leads to the controlled formation of rigid domains bearing a well-packed structure reinforced by hydrogen bonds that are critical for the material's mechanical robustness and stability and the zigzag arrangement of the polymer chains augments self-healing by sliding after damage. This structural design minimizes the risk of premature failure or degradation under stress, thus extending the durability of the material. Importantly, we show that the introduction of chiral domains such as in the co-polymer poly(TUEG3-90-TUCyH-10) can be a promising approach to engineer enhanced stability and sustained self-healing performance in supramolecular polymer materials.

This work presents an innovative strategy in sustainable materials science by converting post-consumer polyethylene terephthalate (PET) into high-performance vitrimers using novel biobased building blocks. Vitrimers, a unique class of polymer networks, combine thermoplastics' reprocessability with thermosets' durability, offering a promising solution to the growing challenges of polymer waste. The research focuses on synthesizing a vitrimeric material by crosslinking Cystamine (CyS) with Epoxidized Polyfarnesene (EpPF), forming a robust polymer network with dynamic disulfide linkages. This vitrimer exhibits exceptional recyclability, thermal stability, and Self-healing capabilities, making it a versatile and sustainable material.

PET waste is chemically integrated into the vitrimer system in the second phase to create a Double Dynamic Network (DDN). The secondary hydroxyl groups generated from the reaction between the epoxy groups in EpPF and the amine groups in CyS interact with the ester linkages in PET. This interaction results in a novel polymer structure that not only enhances the recyclability of PET due to the presence of both disulfide and ester linkages but also provides improved mechanical and thermal performance compared to traditional recycling methods.

This innovative approach bridges renewable resources and waste upcycling, demonstrating how polymer waste can be transformed into advanced materials with potential applications in sustainable packaging, automotive components, and electronics. The study comprehensively analyzes the material’s properties, further supporting its viability as a sustainable alternative.

This work exemplifies the principles of green chemistry and circular economy, offering a promising pathway for reducing environmental issues caused by plastic waste while advancing material innovation

Switchable adhesives are materials of utmost importance due to their capability of having their adhesion/cohesion properties reversibly triggered upon stimuli, allowing on-demand surface attaching/detaching. Still, several challenges mainly associated with complex uncontrolled chemical processes hinders their production. In this study, it is found that unexpectedly vinyl ethers are able to react with thiols in the presence of a catalytic concentration of base, which allows the preparation of well-defined phase-separated switchable adhesives. Indeed, these findings show that base-catalyzed thiol-acrylate and thiol-vinyl ether are highly orthogonal, making the acrylate reaction faster. This is explored to react in the first stage thiols with acrylates in the presence of vinyl ethers to end-cap all the oligomers with stable vinyl ethers and suppress undesirable disulfide formation. In a second stage, the UV-triggered thiol-ene “click reaction” is carried out, forming the network. It is shown that the network prepared by this approach presents superior adhesion due to greater backbone length, a controlled crosslinking motif, and better-defined microphase separation. Additionally, the adhesives made by this strategy are thermo-switchable due to the temperature-triggered base-catalyzed thioether dynamic covalent character at 200 °C. Despite providing superior adhesive properties, the proposed technology endows scalable, thermo-switchable, and O2-resistant adhesives with huge industrialization potential.

Covalently cross-linked elastomers are widely recognised for their excellent elasticity, which makes them essential for a number of applications such as medical implants, tires, seals etc. 1 It is extremely desired to develop flexible and self-healing rubbers since they are capable of being reprocessed to increase their lifespan and reduce environmental pollution 2,3. This work demonstrates a straightforward approach to develop mechanically resilient, healable, and recyclable elastomeric vitrimer based on EPDM (Ethylene Propylene Diene Rubber). This was accomplished by using a dynamic dual cross-linker, which can induce disulphide metathesis as well as transesterification reactions in epoxidized EPDM. In this case, the EPDM was epoxidised to prepare E-EPDM by using meta-chloroperoxybenzoic acid (mCPBA) as an epoxidising agent. The epoxidation of EPDM is confirmed by 1H-NMR and FT-IR analyses. The dynamic dual cross-linker with disulphide linkage bearing dicarboxylic groups, i.e., (4,4'-((disulfanediylbis(4,1-phenylene))bis(azanediyl))bis[4-oxobutanoic acid] (BBO)) was synthesized by reacting of 4-aminophenyl disulphide and succinic anhydride in DMF solvent at ambient temperature under inert atmosphere. The formation of cross-linker was confirmed by 1H-NMR, MALDI-TOF, and FT-IR analyses. The epoxy group of E-EPDM reacted with dicarboxylic groups in BBO to form β-hydroxy ester functional groups, which undergo exchange reaction. This exchange reaction along with the metathesis reaction of disulphide present in BBO installs mechanical resilience, self-healing, and reprocessibility in the modified EPDM.

Covalent Adaptable Networks (CAN) are emerging materials in polymer science, expressing clever examples of chemistry applied to material science. Developments in this field have been witnessing the birth of vitrimers as novel polymer class bridging thermosets to thermoplastic class, offering enhanced recyclability and opportunities for programmable responses to desired external stimuli.[1] CANs are built on covalent bonds which transduce a chemical, light or thermal trigger to a macroscopic physical response. Examples of reversible molecular bond design have been reportedly explored for epoxy resins, polyurethanes and polyimines, unlocking vast functions in optoelectronics, biometrics, sensoristics and smart devices. However, CAN application for functional materials still suffers from unbalanced reactivity-stability affecting mechanical robustness, limiting their implementation thereof.[2] Approaches such as monomer design, nanocomposites and topology optimization are affirmed strategies to tackle the problem and finely tune CAN networks for specific applications. The work we will present aims to explore novel triethanolamine (TEOA) CAN composites with fixed topology and their applicability as smart material. Bio-resourced fillers are the election choice for composite reinforcement in achieving performing TEOA-based CANs with reduced environmental footprint.[3] CAN design consists in a controlled TEOA methacrylation followed by radical (photo)polymerization[4] (Scheme 1), keeping a degree of free transferable hydroxy -OH groups required for the dynamic transesterification (DTER) to happen.[5] Taking advantage of dynamic covalent chemistry and composite design, we will further explore TEOA-based CAN composite's technological possibilities.

To address the need for greener epoxies for 3D printing applications, a vitrimer formed by a bio-based epoxy resin (Cardolite® Lite 514HP) and cystamine was studied. Cystamine was selected as cross-linker due to the presence of disulfide bonds in its molecular structure [1]. Microfibrillated cellulose (MFC) and ultrafine cellulose (UFC) were used as fillers and rheology modifiers to formulate printable pastes. The printing process, based on Liquid Deposition Modeling (LDM), consists of two consecutive steps: printing of the paste and cross-linking in the oven [2]. Cystamine permitted to cure the printed pieces in the 30-80 °C range: this temperature is sufficiently low to prevent collapsing of the piece in the oven and high enough to avoid premature curing during printing. The cross-linking process was studied by DSC and the obtained vitrimers were characterized in terms of gel content, water absorption, and thermal resistance. The printability of the pastes was defined by rheological analysis: 13 wt.% of MFC and UFC were used to make a 3D-printable paste. Stress-relaxation measurements were performed to check bond exchange within the vitrimers, showing a decrease in relaxation time with the addition of cellulose. The vitrimers demonstrated successful mechanical recyclability (1.5 h, 160 °C, 3 metric tons). Finally, a preliminary Life Cycle Assessment was performed to evaluate the environmental impact of the chemicals used and the recycling process.

Vitrimers have been a significant breakthrough in polymer research, with substantial potential for developing high-performance thermosetting plastics that can be reprocessed and recycled. Reprocessable polybenzoxazines combine the beneficial characteristics of polybenzoxazines and vitrimers, such as outstanding thermal stability, mechanical strength, and chemical resistance. They can undergo dynamic covalent bond exchange, allowing for reprocessing and recycling. In contrast, ordinary polybenzoxazines form permanent networks upon curing and cannot be reprocessed or recycled, which poses environmental and economic challenges. To overcome these limitations, researchers have explored adding dynamic covalent chemistry into polybenzoxazines. Specifically, they have integrated reversible imine linkages (C=N) into the polymer framework. The dynamic imine bonds within the network enable rearrangement, making it possible to shape, repair, or recycle the material again. As a result, these polybenzoxazine matrices exhibit behaviour characteristic of vitrimers. Incorporating vitrimer characteristics into carbon fiber reinforced polymer composites offers an innovative combination, enabling the development of eco-friendly composite materials. Polybenzoxazines utilize imine linkages as dynamic bonds, which can be easily formed through a condensation process between aldehydes and primary amines without requiring any catalyst. In conclusion, harnessing the power of dynamic covalent bonds in polybenzoxazinebased carbon fiber reinforced composites presents a groundbreaking solution to the recycling challenges often faced with thermosetting composite materials. This innovative approach not only addresses environmental concerns but also paves the way for the creation of highperformance, sustainable materials

Helical polymers have garnered significant attention for their potential applications in biomedicine. This family of polymers mimics the helical structure, the second most prevalent in nature, and offers advantages such as controlled size, molecular conformation, multivalency, and functionality, in addition to enhancing properties like cell penetration. Despite their promise in areas such as drug delivery, sensing and imaging, and tissue engineering, their use in biomedicine remains limited.

The synthesis of these polymers benefits from relatively straightforward polymerization methods using transition metal complexes. Furthermore, "click chemistry" techniques, such as copper-catalyzed azide-alkyne cycloaddition (CuAAC) or imine formation, facilitate the functionalization of side chains via post-polymerization modification which enables the creation of a broad library of polymers with diverse properties.

Current research is focused on the synthesis and characterization of helical polymers, as well as understanding the design principles governing their molecular architecture. Key challenges moving forward include the precise characterization of the helicity of these materials and the comprehensive evaluation of their biocompatibility.

Keywords: Helical polymers, “click chemistry”, biomedicine

Protective organic coatings on metallic structures are widely employed to prevent the deterioration of metallic structures by corrosion.¹ However, preserving their functions after mechanical damage remains a challenge. To address this, a coating displaying self-healing and anticorrosion properties after damage is prepared by blending a responsive copolymer with ability to release a corrosion inhibitor and a self-healing polyurethane containing disulfide bonds.² The healing and inhibitor-release mechanisms of polymers are activated by disulfide exchange reactions upon heating. The healing efficiency of the anticorrosion properties is exceeding 95% after damage, which reduced the corrosion rate of steel by approximately 24 times compared to a coating containing only self-healing polyurethane without the responsive copolymer.

Polysaccharide-based hydrogels have attracted significant interest for the fabrication of flexible strain sensors because of their renewability, biocompatibility, and biodegradability. However, their widespread application is hindered by the complexity of their manufacturing processes and the inevitable degradation of their mechanical properties with repeated use[1]. The introduction of reversible bond chemistry offers the potential to impart self-healing properties to hydrogels, extending their functional lifespan.
In this study, a starch-based conductive hydrogel (starch/polyvinyl alcohol (PVA)/cellulose nanocrystals (CNCs)) was synthesized via a straightforward one-pot method using borax as a crosslinking agent[2,3]. The hydrogel demonstrated improved mechanical properties and self-healing ability due to the incorporation of CNCs, which formed dual reversible cross-links of hydrogen bonds and borate ester bonds with starch and PVA. Additionally, the presence of abundant sodium ions (Na⁺) and borate ions (B(OH)₄⁻) enhanced the electrical conductivity and strain sensitivity of the hydrogel. The resulting hydrogel demonstrated potential for applications as wearable sensors capable of monitoring a range of human movements, sensing handwriting, and Morse code communication. Notably, the hydrogel demonstrated good remoldability at room temperature after being cut, emphasizing its practical utility in reusability and adaptability. This study broadens the application of starch-based hydrogels in sustainable wearable sensor technologies.

Waterborne binders are widely used in inks and coatings in the packaging industry. Most binders for inks and coatings are acrylate-based polymers derived from unsustainable fossil resources. To become independent of fossil raw materials, as well as moving towards a more circular economy, are important drivers for the development of new bio-based building blocks that have good properties and enhanced recyclability. Dynamic covalent chemistry is being explored to develop new, easily recyclable dynamic polymers of which the properties can be tailored by design. Cyclic 1,2-dithiolanes are perfect candidates to facilitate both as a drop-in replacement and recyclability. These disulfide rings showcase versatile chemical reactivity, enabling various polymerization mechanisms including radical, anionic and cationic ring-opening polymerization. For this work, we want to use the strategy of dynamic covalent bonds to create new sustainable building blocks towards a more circular economy.

Proteins can fold into defined 3D structures which can exhibit unique mechanical properties, such as the elasticity of titin or the stiffness of collagen but are very complex objects. Foldamers, smaller artificial sequence-defined folded molecules, are mechanical elements able to undergo perfectly reversible conformational changes. These molecules unwind and rewind in a fully reversible manner under force while breaking intra-helix sacrificial weak bonds. Recent single-molecule force spectroscopy studies have demonstrated that helical aromatic oligoamides of 8-amino-2-quinolinecarboxylic acid, as small as 1 nm, exhibit exceptional elasticity, surpassing most natural helices. [1] Building on this discovery, our project aims to incorporate these aromatic oligoamides into polymer networks of varying topologies to investigate their impact on the rheological and mechanical properties of polymer gels.
The first targeted topology is an "ideal" network based on a 4-arm poly(ethylene glycol) (PEG) star with norbornene end-groups, enabling efficient conjugation with thiol-functionalized foldamers via photoactivated thiol-ene reaction. The second topology is obtained by cross-linkling linear polymer chains with the thiol-functionalized foldamers. Linear copolymers were synthesized by RAFT polymerization, with 2-methoxyethyl methacrylate as a base monomer and pentafluoro-phenyl acrylate as a comonomer bearing an activated ester moiety. This copolymer was then functionalized with norbornene and subsequently cross-linked by the foldamers. Furthermore, we detail the synthesis of the oligoamide foldamers via solid-phase synthesis. Gels were successfully made using the synthesized pentamer as a cross-linker or emeramide as a non-helical model cross-linker serving as a reference. Rheological measurements and mechanical tensile tests were conducted on the resulting gels.

The use of additive manufacturing methods such as vat photopolymerization (VP) has gained significant popularity over the past two decades and is expected to play a major role in the near future as part of Industry 4.0. However, VP is far from sustainable, in part owing to its fossil-based resins and its non-recyclable products [1].

Vitrimers are stimuli-responsive polymer networks that can undergo bond exchange reactions under specific conditions (e.g., high temperature) [2]. This characteristic gives vitrimers the ability to flow when these conditions are met, but they behave closely to regular thermosets under normal circumstances. Their ability to flow on command could be key in improving the reprocessability of VP products, as it opens up new recycling methods that are impossible with typical thermoset products [3,4].

The goal of this project is to improve the sustainability of VPs by developing a renewable photocurable resin that leads to a recyclable vitrimer material upon curing [5] (Fig. 1.). To accomplish this, a photopolymerizable urethane methacrylate resin is synthesized by using renewable amines and cyclic carbonates derived from supercritical CO2. VP is carried out via stereolithography (SLA) and digital light processing (DLP), with dihydroxypropyl methacrylate as a reactive diluent. After characterization of the printed prototypes, the vitrimer material is recycled repeatedly using the effects of the bond exchange reaction, via a closed-loop process where it is printed again via fused deposition modeling (FDM).

A major factor hindering the recycling of plastics is the use of coatings or adhesives, which are often not designed for substrate removal. This influences the recyclability of the substrate itself. For example, in case a thermoplastic material (remoldable) is coated with a thermoset polymer (not remoldable), the system cannot be recycled properly before separating the coating from the substrate. This requires a significant amount of energy and thus cost, which makes recycling inefficient and an often economically unattractive option in these cases.​1,2​

Vitrimers are a novel class of polymeric materials, with covalent adaptable bonds within their network. These undergo bond exchange reactions, which remain constant at every temperature. However, their lifetime is dependent on stimuli such as temperature, making it possible for vitrimers to transition from a viscoelastic solid to a viscoelastic liquid without a decrease in connectivity. This makes it possible to reprocess vitrimer materials, unlike conventional thermosets.​3,4​

The goal of this project is to establish a polymer system for sustainable coatings, that can be triggered to allow effective removal from a substrate. To achieve this goal, different vitrimer designs based on dynamic transesterification reactions between hydroxyl and ester moieties will be used. To minimize the environmental impact, our strategy utilizes renewable carbon from biomass and CO2 as well as solvent-free photopolymerization directly onto substrates.

To bypass liquid electrolytes, gelified polymer electrolytes (GPEs) have emerged as a promising alternative for electrochemical storage including lithium-metal batteries [1]. GPEs combine the safety and thermal stability of solid electrolytes with the enhanced ionic conductivity of liquid electrolytes, addressing the challenges of dendrite growth and flammability associated with lithium-metal anodes [2]. However, considering recyclability of polymer electrolytes and achieving an optimal balance between mechanical strength and ionic conductivity remain current critical challenges in their development [3].
We have developed of a novel class of dynamic single-ion GPEs based on a plasticized epoxy-acid vitrimer, enriched with polyethylene glycol (PEG) units to provide enhanced chain mobility and flexibility, as shown in Figure 1. The inclusion of a single-ion component ensures efficient ionic conductivity, making the electrolyte highly suitable for advanced energy storage applications Furthermore, the presence of dynamic hydroxyester bonds through transesterification reactions endows the material with reprocessable properties, allowing for potential recycling and repair.
GPEs were thoroughly characterized by Fourier Transform Infrared Spectroscopy and swelling experiments to confirm network formation, as well as rheological measurements to assess gelation and relaxation times, and to gain insights into their viscoelastic properties. Finally, Electrochemical Impedance Spectroscopy was carried out to assess ionic conductivity and electrochemical performance.