Self-healing polymers

Abstract

The present invention relates to self-healing polymers and their uses in various fields such as additive manufacturing and robotics. Furthermore, the present invention relates to methods of making said self-healing polymers, and compositions and structures comprising said polymers.

Description

[Technical field]

[0001] The present invention relates to self-healing polymers and their uses in various fields such as additive manufacturing and robotics. Furthermore, the present invention relates to methods of making said self-healing polymers, and compositions and structures comprising said polymers. [Background technology]

[0002] Any material applied in any kind of application field will undergo some degradation over time. This degradation can be caused, for example, by environmental conditions, damage sustained during operation, or other external factors. Depending on the type of application, different types of materials are suitable, generally selected according to the inherent properties of the material (e.g. weight, stiffness, flexibility, stability, electrical conductivity, porosity). When a material is damaged (e.g. cracks, ruptures, cuts, scratches in the material), external intervention is often required to repair the damage. If the damage is too severe or repairing the damage is disadvantageous (e.g. due to high costs, long repair times), replacement of part or all of the material may be necessary. Overall, materials can be damaged and may require repair over time in order for the material and the parts made of it to continue to function. Therefore, a material that can essentially repair damage can save costs and is very beneficial, especially in areas where parts are frequently damaged or where repair or maintenance is difficult or impossible.

[0003] Robotics, and more specifically, the application of soft grippers, is a prime example of a field that is prone to damage during use. Soft grippers can be deployed in agriculture and food packaging, enabled by embodied intelligence, where the agent's body is responsible for generating the behavior, and control can be outsourced to smart design. When used for fruit and vegetable harvesting, these soft grippers come into close contact with sharp objects (e.g., sharp twigs, thorns, plastic or glass). As a result, macroscopic damage (e.g., punctures, cuts and ruptures) occurs over time, negatively affecting the performance of these grippers. Typically, these soft grippers are manufactured from relatively cheap materials such as elastomers (e.g., silicone, polyurethane), which means that damaged grippers are replaced rather than repaired. However, this requires a significant amount of new resources, along with time-consuming and costly human intervention. Moreover, waste is generated over time, resulting in significant environmental impacts. Due to their shortcomings, the use of self-healing materials can be considered as a promising alternative that minimizes external intervention and repairs damaged materials, eliminating the need for replacement of the materials.

[0004] Robots are also used in remote applications such as search-and-recovery or environmental surveys in (aero)space or marine environments, where damaged parts are difficult to repair or replace. Soft robots have the advantage of being safer because they can bend, stretch and twist around obstacles, but the disadvantage is that they are difficult to control due to their infinite degrees of freedom.

[0005] Self-repairing materials already exist today, making it possible to repair damage without the need to replace these materials. However, some drawbacks are known. In the case of extrinsic repair systems that rely on the encapsulation of repair agents, the repair action may often only occur a limited number of times at the same damage site. Also, the repair mechanisms are often not suitable for repairing damage of a significant size. Moreover, these repair mechanisms are only available in hard materials and do not offer the flexibility that is so beneficial for the construction of soft grippers, for example. In many endogenous repair systems, the strength of the materials is often insufficient to produce larger 2D or 3D structures that have sufficient strength and retain their structural integrity.

[0006] A particular type of self-healing material is the Diels-Alder (DA) polymer network, which offers a solution to most of the above-mentioned shortcomings. This network is based on the reversible Diels-Alder reaction of functional diene (e.g., furan) groups with dienophile (e.g., maleimide) groups, which realizes the self-healing properties. The crosslinking process within these polymers is the most important aspect of the particular self-healing properties of Diels-Alder-based polymers based on strong covalent bonds, allowing the production of 1D, 2D or 3D structures with sufficient mechanical strength even after self-healing. In the applicant's previous work (Patent Document 1), we have developed new Diels-Alder polymer networks with self-healing capabilities even at room temperature or below without the need for external intervention.

[0007] However, as Hawkes et al. (1) recently noted, there are several significant challenges that must be overcome before soft robotics can be widely adopted, one of which is sustainability. Currently, soft robots do not offer a sustainable solution because (i) the materials used in their manufacture are fossil-based, and (ii) they are also usually made from chemically cross-linked materials that are less recyclable and biodegradable. The key to a successful sustainable design is to start with the right choice of materials. For this reason, as Kaltenbrunner et al. (2) noted in their review, both the fields of soft robotics and materials science should move forward in terms of reducing their ecological footprint, both by developing new materials that contribute to a more sustainable future, and by improving existing materials. The reliance of soft robotics on fossil-based, poorly degradable polymeric materials clearly raises environmental concerns. Although bioplastics production capacity is growing at a significant pace, from about 2.11 million tonnes in 2018 to 2.62 million tonnes in 2023, it will still account for less than 1% of the 335 million tonnes of plastics produced annually. Moreover, the use of renewable raw materials primarily addresses the resource issue, not necessarily the waste issue.

[0008] In the literature, there have been several attempts to improve the sustainability of self-healing Diels-Alder networks. Yoshie et al. (Non-Patent Document 3) developed a bio-based polyester that can recover stress at break up to 18 MPa upon mild heating at 50 °C for 5 days. Gandini et al. (Non-Patent Document 4) focused on the use of vegetable oils and highlighted the possibility of using several oils and furan monomers for self-healing applications. Feng et al. (Non-Patent Document 5) functionalized epoxidized natural rubber with furfurylamine to obtain a material that was reprocessable and healed 87% upon heating at 150 °C. Recently, Wu et al. (Non-Patent Document 6) reported the synthesis of a self-healing CO2-based polyurethane urea DA that heals itself with up to 94% efficiency upon heating at 120 °C for 10 min and 60 °C for 24 h. In all these cases, only one or two sustainability aspects were focused on, while the others were ignored. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent Application Publication No. 20192135.0 [Non-patent literature]

[0010] [Non-Patent Document 1] Sci. Robot. 2021, 6, eabg6049 [Non-Patent Document 2] Adv. Mater. 2021, 33, 2004413 [Non-Patent Document 3] Polym. Degrad. Stab. 2019, 161, 13 [Non-Patent Document 4] Eur. J. Lipid Sci. Technol. 2018, 120, 1700091 [Non-Patent Document 5] ACS Appl. Polym. Mater. 2019, 1, 169 [Non-Patent Document 6] Green Chem. 2021, 23, 552 Summary of the Invention [Problem to be solved by the invention]

[0011] It is therefore an object of the present invention to address these issues from a more holistic perspective by providing new, sustainable, self-healing polymers, thereby optimizing the renewable, biodegradable and recyclable nature of these polymers as a whole. [Means for solving the problem]

[0012] According to a first aspect, the present invention provides a Diels-Alder type polymer comprising the reaction product of polymaleimide monomer units and a furan-functionalized prepolymer, the furan-functionalized prepolymer comprising a central moiety according to formula (I): [ka] (In the formula, R 1 is -H), wherein at least one furan-functionalized side chain is attached to a central moiety, and the prepolymer backbone is based on a polyester.

[0013] According to one embodiment of the present invention, the furan-functionalized side chains are directly attached to the central moiety and have the structure according to formula (II). [ka] (In the formula, A is -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 alkyl-O-, -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 Each alkyl-O- is optionally and independently selected from -halo, -OH, -C1~6 Alkyl, -C 1~6 Alkenyl, and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, B is selected from -C(O)O- and -O(O)C-; k is an integer selected from 0, 1, and 2; l is an integer selected from 0 and 1; m is an integer selected from 0, 1, 2, 3, 4, and 5.

[0014] According to one embodiment of the present invention, the central moiety of formula (I) is directly attached to the prepolymer backbone.

[0015] According to one embodiment of the invention, the central moiety of formula (I) is [ka] (In the formula, X is -C 1~6 Alkyl- and -C 2~6 alkenyl-, -C 1~6 Alkyl- and -C 2~6 Each alkenyl- is optionally and independently selected from -halo, -OH, -C 1~6 Alkyl, -C 1~6 Alkenyl and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, Y is selected from -C(O)O- and -O(O)C-; Z is selected from -O- and -C(O)O-; a is an integer selected from 0, 1, and 2; and b is an integer selected from 0 and 1.

[0016] According to one embodiment of the present invention, both the polymaleimide monomer unit and the furan-functionalized prepolymer have a functionality of at least 2, and the sum of the functionalities of both the polymaleimide monomer unit and the furan-functionalized prepolymer is at least 4.6.

[0017] According to one embodiment of the present invention, the stoichiometric ratio of maleimide to furan between the polymaleimide monomer unit and the furan-functionalized prepolymer ranges from 1 to 0.25, preferably from 1 to 0.6.

[0018] According to one embodiment of the invention, the polymaleimide is selected from the list comprising 1,1'-(methylenedi-4,1-phenylene)bismaleimide, N,N'-(1,4-phenylene)dimaleimide, N,N'-(1,3-phenylene)dimaleimide, bismaleimide, etc.

[0019] According to another aspect, the present invention provides a composition comprising a Diels-Alder type polymer as defined herein.

[0020] According to one embodiment of the invention, the composition further comprises a radical scavenger. According to a particular embodiment of the invention, the radical scavenger is selected from the list comprising hydroquinone butylated hydroxytoluene, 4-tert-butylcatechol, methyl-p-benzoquinone, etc.

[0021] According to another aspect, the present invention provides a method for producing a Diels-Alder type polymer as defined herein, the method comprising the step of preparing a composition comprising polymaleimide monomer units and a furan-functionalized prepolymer.

[0022] According to yet another aspect, the present invention provides the use of a Diels-Alder type polymer or composition according to the invention.

[0023] According to a further embodiment, the present invention provides the use of a Diels-Alder type polymer or composition as a self-healing material.

[0024] According to a further embodiment, the present invention provides the use of the Diels-Alder type polymer or composition in robotics or biomedicine.

[0025] According to a further embodiment, the present invention provides the use of a Diels-Alder type polymer or composition in the manufacture of 1D, 2D or 3D structures, more particularly in the manufacture of robotic components.

[0026] According to further embodiments, the present invention provides the use of Diels-Alder type polymers or compositions in filament extrusion, extrusion-based printing techniques, selective laser sintering, injection molding, compression molding, casting, soft lithography, etc. According to a particular embodiment of the present invention, the extrusion-based printing technique is selected from the list comprising fused filament fabrication, direct ink writing, etc.

[0027] According to another aspect, the present invention provides a 1D, 2D or 3D structure comprising a Diels-Alder type polymer or composition as defined herein.

[0028] With specific reference now to the figures, it is emphasized that the details shown are by way of example and for the purpose of illustrative discussion of different embodiments of the present invention only. They are presented to provide what is believed to be the most useful and facile explanation of the principles and conceptual aspects of the present invention. In this regard, no attempt has been made to show structural details of the present invention in more detail than is necessary for a fundamental understanding of the present invention. The description, together with the drawings, will make apparent to those skilled in the art how some forms of the present invention may be embodied in practice. [Brief description of the drawings]

[0029] [Figure 1]FIG. 2 shows a chemical Diels-Alder reaction scheme between a furan A group and a maleimide B group to give a Diels-Alder reaction product C according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram of hydrogen bonding between different central moieties according to an embodiment of the present invention. [Diagram 3] 1H NMR spectra of castor oil (CO), maleinized castor oil (mCO) and furan-functionalized maleinized castor oil (FmCO). [Figure 4] 1H NMR spectra of succinized castor oil (sCO), itaconized castor oil (iCO), citraconized castor oil (cCO), and maleated castor oil (mCO). During the reaction, some of the itaconic anhydride becomes citraconic anhydride. Therefore, a peak corresponding to citraconized castor oil can be seen in the reaction product of itaconic anhydride and castor oil. [Diagram 5] 1H NMR spectra of furan-functionalized succinylated castor oil (FsCO), furan-functionalized itaconized castor oil (FiCO), furan-functionalized citraconized castor oil (FcCO), and furan-functionalized maleic castor oil (FmCO). [Figure 6] Figure 1 shows the mechanical properties of the intact materials: Stress-strain curves of a) a furan-functionalized material based on three anhydrides (FmCO, FiCO, and FsCO) and DPBM (r=1), b) a furan-functionalized itaconized castor oil (FiCO) reacted with DPBM at different furan / maleimide molar ratios, and c) a furan-functionalized material based on three anhydrides (FmCO, FiCO, and FsCO) and the liquid bismaleimide BMI-689 (r=1). [Figure 7]a) Dynamic rheometry results from room temperature to 130 °C of furan-functionalized maleated castor oil (FmCO) (r=1) reacted with BMI-689, and b) DSC thermograms of furan-functionalized succinated castor oil (FsCO) reacted with 1,1'-(methylenedi-4,1-phenylene) bismaleimide (DPBM) at different furan / maleimide molar ratios. [Figure 8] 1 shows a) dynamic rheometry results from 50° C. to 130° C. of furan-functionalized epoxidized soybean oil (FAcSO) reacted with BMI-689 according to Comparative Example A, and b) DSC thermogram. [Figure 9] FIG. 13 is a DSC thermogram of furan-functionalized epoxidized soybean oil (sFASO) reacted with BMI-689 according to Comparative Example B. [Figure 10] FIG. 13 shows the self-repair of FsCO-DPBM (r=0.8) over time. [Figure 11] FIG. 14. Mechanical and self-healing properties of FmCO-DPBM (r=0.8) material (before and after retreatment) after three consecutive retreatment cycles. On the left are the obtained values ​​for elongation or ultimate tensile stress and on the right the corresponding self-healing efficiency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention will be further described below. In the following paragraphs, the various aspects of the present invention are defined in more detail. Each aspect so defined can be combined with any other aspect or aspects, unless expressly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous can be combined with any other feature or features indicated as being preferred or advantageous.

[0031] When describing the compounds of the present invention, the terms used should be construed in accordance with the following definitions, unless the context dictates otherwise.

[0032] The term “alkyl” by itself or as part of another substituent refers to a group of the formula Cx H 2x Or C x H 2x+1 where x is a number equal to or greater than 1. Generally, alkyl groups of the present invention contain 1 to 20 carbon atoms. Alkyl groups may be straight or branched chain and may be substituted as provided herein. When a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the designated group may contain. Thus, for example, C 1~4 Alkyl means alkyl of 1 to 4 carbon atoms. Examples of alkyl groups are methyl, ethyl, n-propyl, i-propyl, butyl and its isomers (e.g., n-butyl, i-butyl and t-butyl); pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers; decyl and its isomers. C1-C6 alkyl includes all linear, branched or cyclic alkyl groups containing 1 to 6 carbon atoms, thus including methyl, ethyl, n-propyl, i-propyl, butyl and its isomers (e.g., n-butyl, i-butyl and t-butyl); pentyl and its isomers, hexyl and its isomers, cyclopentyl, 2-, 3- or 4-methylcyclopentyl, cyclopentylmethylene, and cyclohexyl. Optionally substituted alkyl refers to an alkyl optionally having one or more (eg, 1, 2, 3, or 4) substituents.

[0033] The term "alkenyl" by itself or as part of another substituent refers to a straight, cyclic, or branched chain hydrocarbon radical containing at least one carbon-carbon double bond. Thus, for example, C 2~4Alkenyl refers to an alkenyl of 2 to 4 carbon atoms. Examples of alkenyl radicals include ethenyl (vinyl), E- and Z-propenyl, allyl, isopropenyl, E- and Z-butenyl, E- and Z-isobutenyl, E- and Z-pentenyl, E- and Z-hexenyl, E,E-, E,Z-, Z,E-, Z,Z-hexadienyl, and the like. Optionally substituted alkenyl refers to an alkenyl optionally having one or more (e.g., one, two, three, or four) substituents. C1 alkenyl refers to a vinyl moiety in which the C1 substituent, together with the carbon to which it is attached, forms a carbon-carbon double bond.

[0034] When used in the present invention, the term "compounds of the invention" or similar terms is always meant to include the compounds of general formula (I) and any subgroups thereof. This term also refers to their derivatives, such as solvates, hydrates, stereoisomers, racemic mixtures, tautomers and optical isomers.

[0035] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. By way of example, "a compound" means one compound or more than one compound. The above terms, and others used herein, are well understood by those of ordinary skill in the art. Compounds of the invention can be prepared according to the reaction schemes presented in the examples below, but those of ordinary skill in the art will appreciate that these are merely illustrative of the invention and that compounds of the invention can be prepared by any of several standard synthetic processes commonly used by those of ordinary skill in the art of organic chemistry.

[0036] According to a first aspect, the present invention provides a Diels-Alder type polymer comprising the reaction product of polymaleimide monomer units and a furan-functionalized prepolymer, the furan-functionalized prepolymer comprising a central moiety according to formula (I): [ka] (In the formula, R 1 is -H), wherein at least one furan-functionalized side chain is attached to a central moiety, and the prepolymer backbone is based on a polyester.

[0037] As stated herein, unless otherwise specified, the term "Diel-Alder type polymer" is to be understood as a polymer network formed by the Diels-Alder reaction of furan with maleimide, containing reversible covalent crosslinks (referred to as "Diels-Alder bonds") resulting in either isomer of the cycloadduct. The network structure is formed using two reactive moieties, a furan-functionalized prepolymer and a polymaleimide, in particular a bismaleimide. The Diels-Alder reaction forming the Diels-Alder bonds is an equilibrium reaction that makes the formed crosslinks dynamic. The bonds are constantly broken and reformed in the dynamic network over time. However, the crosslink density can be defined for a specific temperature, provided there is no temperature change.

[0038] When the Diels-Alder network is damaged, the Diels-Alder bonds and hydrogen bond interactions are reversibly and locally broken, resulting in an active fracture surface. The hydrogen donors and acceptors, as well as the newly formed furan and maleimide functionalities, resulting from the reversible mechanical severing of the Diels-Alder bonds, autonomously reform the broken bonds, thus restoring the polymer network structure and associated properties. The repair process is accelerated synergistically by the presence of hydrogen bonds in the vicinity of the Diels-Alder bonds. To achieve this repair of the damaged area, the first part of the self-repair process is to bring the fracture surfaces back into contact. Depending on the magnitude of the damage, for example, if the material is completely cut and two separate pieces are formed, manual intervention or intervention by a robotic system may be required to actively push both fracture surfaces back together. Such a complete cut requires that both broken pieces be pushed back together to initiate the repair process. In this case, it is important to push both pieces back together as soon as possible after the damage has occurred.

[0039] The fracture surfaces are contacted as soon as possible after damage has occurred, preferably within 1-2 hours. Otherwise, the available reactive groups (maleimide and furan) will react with each other on the separate moieties, reducing the rate and efficiency of repair under the given repair conditions. Nevertheless, moieties separated for longer periods can be repaired with high efficiency if the repair time or temperature is significantly extended.

[0040] After the fractured surfaces are reassembled (autonomously or non-autonomously), the self-repair process starts. At this point, there is a risk of micro-displacements and small cavities occurring between the fractured surfaces. Here, the synergistic combination of the weak hydrogen bond interactions of the present invention with the dynamic Diels-Alder covalent bonds (Figures 1 and 2) plays a key role. On the one hand, if the material is damaged, the weak hydrogen bonds help to instantly recover some of the mechanical properties, ensuring good contact and immediate adhesion when the cracked surfaces come into contact again. On the other hand, the Diels-Alder bonds contribute significantly to the mechanical properties and prevent or reduce creep.

[0041] The specific structure of the core that provides the hydrogen acceptor (carbonyl group) and hydrogen donor (hydroxy group) is key to the self-healing properties of the present invention.

[0042] Due to the reversibility of Diels-Alder and hydrogen bonds, the polymer network structure can be reversibly polymerized and depolymerized, and therefore the material can be thermally treated, manufactured, and recycled by common thermal and chemical processing methods.

[0043] As used herein, unless otherwise specified, the term "self-repair efficiency" is understood as the recovery of material properties (e.g., mechanical strength) and is measured by the ratio of the measured properties after repair to the original material properties before damage. Repair efficiency is based on, for example, mechanical modulus, mechanical strength, characterized by fracture stress and fracture strain. The efficiency can be expressed as a percentage.

[0044] As used herein, unless otherwise specified, the concept of "autonomous self-repair" shall be understood as the ability of a self-repairing material (e.g., a Diels-Alder type polymer) to repair itself upon damage when a fracture surface is in contact without the need for any kind of external intervention (e.g., the need for an elevated temperature).

[0045] According to some embodiments of the invention, self-repair occurs at temperatures below 30°C, 29°C, 28°C, 27°C, 26°C, 25°C, 24°C, 23°C, 22°C, 21°C, 20°C, 19°C, 18°C, 17°C, 16°C, 15°C, 14°C, 13°C, 12°C, 11°C, 10°C, 5°C.

[0046] According to some embodiments of the invention, self-healing can occur at temperatures of about 10° C., 15° C., 20° C.-30° C., 40° C., 50° C., particularly about 15° C., 20° C., 25° C.-30° C., 35° C., 40° C. According to some embodiments of the invention, the self-healing efficiency may increase with increasing temperature, but the characteristic of the Diels-Alder type polymers according to the invention that the self-healing process can occur at these lower ambient temperatures remains.

[0047] According to some embodiments of the present invention, self-healing efficiencies of about 80%, 90%, 100%, in particular about 90%, 95%, 99% can be achieved at room temperature. Self-healing efficiencies of about 70%, 80% are already realized after about 1-2 days at about 25°C. Self-healing efficiencies of about 96%, 97%, 98% are already realized after about 7 days at about 25°C. It should be noted that while a 100% healing efficiency means that the full mechanical and fracture properties of the material are restored, properties required for practical use can be restored in much shorter times.

[0048] The advantage of the present invention is that Diels-Alder type polymers possess both the necessary chain mobility within the network and a sufficient concentration of reactive moieties (Diels-Alder bonds and hydrogen bonds) to repair macroscopic damage at room temperature with high repair efficiency and at a reasonable rate.

[0049] According to some embodiments of the invention, the repair time can range from a few minutes to a few hours to a few days, more specifically from about 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60 minutes to about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30 days. In addition to temperature, the time of self-repair also affects the repair efficiency. The longer the damaged material has to repair itself (i.e., keep the fracture surfaces in good contact), the higher the repair efficiency at a given temperature. Aspects such as maleimide to furan ratio, available reactive groups, flexibility of the monomer units, crosslink density, molecular mobility, repair temperature, and the time between fracture and contact of the fracture surfaces, among others, can affect the repair time required to achieve a certain repair efficiency. According to some embodiments of the invention, the repair time can be reduced by increasing the repair temperature. However, an advantage of embodiments of the invention is that repair can occur at room temperature or below.

[0050] According to some embodiments of the present invention, damaged surfaces of Diels-Alder type polymers can be fully restored in that they fully regain the original strength of the Diels-Alder type polymer. With reference to the examples below, it has been found that such fully restored original strength of the Diels-Alder type polymer occurs particularly when the fractured surfaces realign when they come into contact with each other.

[0051] The prepolymer backbone of the furan-functionalized prepolymer can be based on any suitable polyester. Examples of such suitable polyesters are natural fatty acid esters or condensation products of fatty acids or their mixtures with fatty acid polyols. The polyols can be selected, for example, from 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol and dipentaerythritol. The fatty acids can be selected, for example, from unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid, or hydroxy fatty acids such as 12-hydroxystearic acid, 12-hydroxyoctadec-9-enoic acid and 14-hydroxyicos-11-enoic acid. Other examples of suitable polyesters are the condensation products of aliphatic or aromatic polyols with aliphatic or aromatic polycarboxylic acids, the condensation products of hydroxy fatty acids, or polyesters obtained by other polymerization means such as, but not limited to, ring-opening polymerization of lactones.

[0052] According to one embodiment of the present invention, the furan-functionalized side chains are directly attached to the central moiety and have the structure according to formula (II). [ka] (In the formula, A is -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 alkyl-O-, -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 Each alkyl-O- is optionally and independently selected from -halo, -OH, -C 1~6 Alkyl, -C 1~6 Alkenyl, and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, B is selected from -C(O)O- and -O(O)C-; k is an integer selected from 0, 1, and 2; l is an integer selected from 0 and 1; m is an integer selected from 0, 1, 2, 3, 4, and 5.

[0053] According to one embodiment of the present invention, the central moiety of formula (I) is attached directly to the prepolymer backbone.

[0054] According to one embodiment of the present invention, the central moiety of formula (I) is a linker structure according to formula (III). [ka] (In the formula, X is -C 1~6 Alkyl- and -C 2~6 alkenyl-, -C 1~6 Alkyl- and -C 2~6 Each alkenyl- is optionally and independently selected from -halo, -OH, -C 1~6 Alkyl, -C 1~6 Alkenyl and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, Y is selected from -C(O)O- and -O(O)C-; Z is selected from -O- and -C(O)O-; a is an integer selected from 0, 1, and 2; and b is an integer selected from 0 and 1.

[0055] According to certain embodiments of the present invention, there is provided a Diels-Alder type polymer comprising the reaction product of polymaleimide monomer units and a furan-functionalized prepolymer, The furan-functionalized prepolymer comprises a central moiety according to formula (I) [ka] (In the formula, R 1is -H), wherein at least one furan-functionalized side chain is directly attached to a central moiety, and the prepolymer backbone is polyester-based; At least one furan-functionalized side chain according to formula (II) [ka] (In the formula, A is -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 alkyl-O-, -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 Each alkyl-O- is optionally and independently selected from -halo, -OH, -C 1~6 Alkyl, -C 1~6 Alkenyl, and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, B is selected from -C(O)O- and -O(O)C-; k is an integer selected from 0, 1, and 2; l is an integer selected from 0 and 1; wherein m is an integer selected from 0, 1, 2, 3, 4, 5) is directly attached to the central moiety of formula (I).

[0056] According to another particular embodiment of the present invention, there is provided a Diels-Alder type polymer comprising the reaction product of polymaleimide monomer units and a furan-functionalized prepolymer, The furan-functionalized prepolymer comprises a central moiety according to formula (I) [ka] (In the formula, R 1 is -H), wherein at least one furan-functionalized side chain is attached to a central moiety, and the prepolymer backbone is polyester-based; At least one furan-functionalized side chain according to formula (II) [ka] (In the formula, A is -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 alkyl-O-, -C 1~6 Alkyl-, -C 2~6 Alkenyl- and -C 1~6 Each alkyl-O- is optionally and independently selected from -halo, -OH, -C 1~6 Alkyl, -C 1~6 Alkenyl, and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, B is selected from -C(O)O- and -O(O)C-; k is an integer selected from 0, 1, and 2; l is an integer selected from 0 and 1; m is an integer selected from 0, 1, 2, 3, 4, and 5) is directly attached to the central moiety; The central part is a linker structure according to formula (III) [ka] (In the formula, X is -C 1~6 Alkyl- and -C 2~6 alkenyl-, -C 1~6 Alkyl- and -C 2~6 Each alkenyl- is optionally and independently selected from -halo, -OH, -C 1~6 Alkyl, -C 1~6 Alkenyl and -OC 1~6 substituted with 1 to 3 substituents selected from alkyl, Y is selected from -C(O)O- and -O(O)C-; Z is selected from -O- and -C(O)O-; a is an integer selected from 0, 1, and 2; and b is an integer selected from 0 and 1, and is attached to the prepolymer backbone via a tert-butyl group.

[0057] Scheme 1 presents a reaction scheme for the preparation of a Diels-Alder type polymer starting from castor oil (CO) and itaconic anhydride (IA), further reacting with furfuryl glycidyl ether (FGE) and finally crosslinking with DPBM according to a particular embodiment of the present invention. [ka] First step 1 st step No solvent 90℃ overnight Second step 2 nd step No solvent 120℃ overnight Crosslinking Room temperature RT Degradability Recyclability & Self-healing Scheme 1

[0058] According to one embodiment of the present invention, both the polymaleimide monomer unit and the furan-functionalized prepolymer have a functionality of at least 2, and the sum of the functionalities of both the polymaleimide monomer unit and the furan-functionalized prepolymer is at least 4.6.

[0059] Unless otherwise specified, functionality shall be understood as the number of maleimide or furan groups in the polymaleimide monomer unit and the furan-functionalized prepolymer, respectively.

[0060] According to one embodiment of the present invention, the stoichiometric ratio of maleimide to furan between the polymaleimide monomer unit and the furan-functionalized prepolymer ranges from 1 to 0.25, preferably from 1 to 0.6.

[0061] Unless otherwise specified, the stoichiometric ratio (r) of maleimide to furan shall be understood as the molar ratio of maleimide groups to furan groups.

[0062] According to one embodiment of the present invention, the polymaleimide is selected from the list comprising 1,1'-(methylenedi-4,1-phenylene)bismaleimide (DPBM), N,N'-(1,4-phenylene)dimaleimide, N,N'-(1,3-phenylene)dimaleimide, bismaleimide, Homide 122G, Homide 116, BMI-689, BMI-1400, BMI-1700, etc.

[0063] According to another aspect, the present invention provides a composition comprising a Diels-Alder type polymer as defined herein.

[0064] According to some embodiments of the present invention, the composition further comprises a radical scavenger. According to certain embodiments of the present invention, the radical scavenger is selected from the list comprising hydroquinone butylated hydroxytoluene, 4-tert-butylcatechol, methyl-p-benzoquinone, etc. According to some embodiments of the present invention, the composition may further comprise an additive, which adds functionality or properties to the reaction product, such as color, texture, tactile experience, flexibility, processability, viscosity at higher temperatures, electrical properties, or magnetic properties.

[0065] According to another aspect, the present invention provides a method for producing a Diels-Alder type polymer as defined herein, the method comprising the step of preparing a composition comprising polymaleimide monomer units and a furan-functionalized prepolymer.

[0066] According to yet another aspect, the present invention provides the use of a Diels-Alder type polymer or composition according to the invention.

[0067] According to a further embodiment, the present invention provides the use of a Diels-Alder type polymer or composition as a self-healing material.

[0068] According to a further embodiment, the present invention provides the use of the Diels-Alder type polymer or composition in robotics or biomedicine.

[0069] According to some embodiments of the present invention, the use in robotics may constitute a subfield of soft robotics. As used herein, unless otherwise specified, the term "soft robotics" is to be understood as a subfield of robotics that involves building robot parts and robots from a variety of materials that approximate the properties found in living organisms. These materials often require a certain degree of flexibility and adaptability for specific purposes.

[0070] As mentioned above, an example of a robotic system is the manufacture of soft robotic systems, such as soft grippers that can be used in agriculture, for example, for harvesting fruit. In such situations, the material of these soft grippers must be capable of handling delicate fruits (e.g., strawberries) without damaging them. However, in such situations, it is inevitable that these soft grippers will be damaged, for example, by sharp twigs and thorns. This is just one example where the specific properties of self-healing Diels-Alder type polymers can bring great advantages when applied in the field of robotics.

[0071] According to some embodiments of the present invention, the soft robotics actuators can include bending soft pneumatic actuators (BSPAs) that can assume several bending shapes. These BSPAs can be used together as finger structures of the soft robotic system, such as soft grippers, among others. Due to their bendability, the finger structures can move in a way that mimics human-like hand gestures.

[0072] According to a further embodiment, the present invention provides the use of a Diels-Alder type polymer or composition in the manufacture of 1D, 2D or 3D structures, more particularly in the manufacture of robotic components.

[0073] According to further embodiments, the present invention provides the use of the Diels-Alder type polymer or composition in filament extrusion, extrusion-based printing techniques, selective laser sintering, injection molding, compression molding, cast molding, soft lithography, etc. According to a particular embodiment of the present invention, the extrusion-based printing technique is selected from the list comprising fused filament fabrication, direct ink writing, etc.

[0074] According to another aspect, the present invention provides a 1D, 2D or 3D structure comprising a Diels-Alder type polymer or composition as defined herein.

[0075] The compounds of the present invention can be prepared according to the method(s) presented in the following examples, but those skilled in the art will understand that these are merely illustrative of the invention and that the compounds of the present invention can be prepared by any of a number of standard synthetic processes commonly used by those skilled in the art of organic chemistry.

[0076] As described herein above, the self-healing properties of Diels-Alder polymers are based on the reversible crosslinking reaction of furan-functionalized prepolymers according to formula (I) with polymaleimides. Figure 1 shows the reversible Diels-Alder reaction scheme between furan A groups and maleimide B groups, resulting in Diels-Alder reaction product C. The reversible Diels-Alder polymer network is based on the reversible Diels-Alder reaction of functional furan A groups with maleimide B groups, resulting in strong covalent bonds that can be thermally or mechanically broken and reversibly reformed, achieving the self-healing properties. EXAMPLES

[0077] material Succinic anhydride (SA), itaconic anhydride (IA), maleic anhydride (MA), castor oil (CO, 164 mg KOH / g), furfuryl alcohol (FA), 3-furan carboxylic acid (FAc), and 1,1'-(methylenedi-4,1-phenylene) bismaleimide (DPBM) were obtained from Sigma Aldrich. 4-tert-Butylcatechol was used as a radical inhibitor and was obtained from Sigma Aldrich. Furfuryl glycidyl ether (FGE) was obtained from Sage Chemicals (Hangzhou, China). Epoxidized soybean oil (SO) was obtained from Varteco (Santa Fe, Argentina). BMI-689 was obtained from Designer molecules (Willow Creek, San Diego). All products were used as received.

[0078] analysis Bruker Avance DRX 250 with aperture frequency of 250 MHz 1 H NMR was performed. The analysis was carried out at room temperature using CDCl3 as the solvent and TMS as the internal standard. The concentration of the measured sample was 10 mg m -1 It was decided.

[0079] Fourier transform infrared (FTIR) spectroscopy was performed at ambient temperature on a Thermo Scientific Nicolet 6700 FTIR spectrophotometer using OMNIC as the software package. All spectra were recorded at 4000 cm -1 ~600cm -1 The results are averaged from 32 scans recorded at 100 Hz.

[0080] GPC analysis was performed on a Shimadzu system using a combination of Styragel HR0.5 and HR1 columns connected to a RID and UV detector. The instrument was calibrated with polystyrene internal standards and eluted with tetrahydrofuran (THF).

[0081] Differential scanning calorimetry (DSC) was performed on a TA Instruments Discovery DSC equipped with a refrigerated cooling system (RCS). All experiments were carried out in Tzero aluminum pans in closed conditions using nitrogen as purge gas and heating / cooling rates of 5° C. / min.

[0082] Dynamic mechanical analysis (DMA) was performed on a TA Instruments DMA Q800 equipped with a nitrogen gas cooling accessory. Stress-strain tensile tests were performed at room temperature using a film tension clamp. Rectangular specimens with a thickness of 1.25 mm and width of 5 mm were clamped with a distance of 5 mm between the clamps and strained at a rate of 60% / min. Young's modulus was determined in the initial linear region of the stress-strain curve (0%-1% strain). To investigate the viscoelastic properties, samples were subjected to small amplitude oscillatory measurements at a frequency of 1 Hz and strain of 0.1%, with heating and cooling cycles at a rate of 2°C / min from -80°C to 90°C.

[0083] Dynamic rheometry was performed using a TA Instruments Discovery Hybrid Rheometer (DHR2). Samples were cut into circular shapes and placed between aluminum parallel plates with a diameter of 10 mm. The samples were subjected to 5% oscillatory strain at different frequencies: 0.312 Hz, 0.562 Hz, 1.0 Hz, 1.778 Hz, and 3.125 Hz. Simultaneously, they were subjected to a temperature gradient from 40 °C to 120 °C to determine the gelation transition temperature.

[0084] To perform the accelerated in vitro degradation study, three squares of 10 mm x 10 mm x 1.25 mm were cut for each sample and placed in KCl NaOH buffer at pH 13 and temperature 37° C. for 14 days. Samples were dried and weighed every day to measure mass loss.

[0085] synthesis Example 1 Maleic anhydride (MA) was used to carry out the ring-opening esterification of castor oil. The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. A molar ratio of hydroxyl groups of castor oil to anhydride of 1:1 was used. The esterification reaction was carried out at 100°C for 24 hours. The resulting maleated castor oil (mCO) was used without any further purification.

[0086] Example 2 Itaconic anhydride (IA) was used to carry out the ring-opening esterification of castor oil. The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. A molar ratio of hydroxyl groups of castor oil to anhydride of 1:1 was used. The esterification reaction was carried out at 100°C for 24 hours. The obtained itaconic castor oil (iCO) was used without any further purification.

[0087] Example 3 Ring-opening esterification of castor oil was carried out using succinic anhydride (SA). The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. A molar ratio of hydroxyl groups of castor oil to anhydride of 1:1 was used. The esterification reaction was carried out at 130°C for 24 hours. The resulting succinylated castor oil (sCO) was used without any further purification.

[0088] Example 4 Furfuryl glycidyl ether (FGE) was mixed directly with mCO in a 1:1 molar ratio with respect to the anhydride. The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. The functionalization was carried out at 120 °C overnight. The resulting furan-functionalized maleated castor oil (FmCO) was used in the next step without any further purification.

[0089] Example 5 Furfuryl glycidyl ether (FGE) was mixed directly with iCO in a 1:1 molar ratio to the anhydride. The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. The functionalization was carried out at 120 °C overnight. The resulting furan-functionalized itaconized castor oil (FiCO) was used in the next step without any further purification.

[0090] Example 6 Furfuryl glycidyl ether (FGE) was mixed directly with sCO in a 1:1 molar ratio with respect to the anhydride. The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. The functionalization was carried out at 120 °C overnight. The resulting furan-functionalized succinylated castor oil (FsCO) was used in the next step without any further purification.

[0091] Example 7 FmCO, FiCO and FsCO were crosslinked using two different bismaleimides: 1,1′-(methylenedi-4,1-phenylene) bismaleimide (DPBM) and a commercial low-viscosity bismaleimide derived from fatty acids (BMI-689).

[0092] To prepare the DPBM crosslinked networks, the functionalized castor oil samples were placed in separate beakers and DPBM was added to the mixture, providing three different molar ratios of furan to maleimide groups for each functionalized oil (1:1, 1:0.8, and 1:0.6). Finally, 1 wt.% of 4-tert-butylcatechol was added to prevent radical side reactions between the maleimide groups. The mixture was heated until the DPBM melted and a homogeneous solution with the functionalized oil was formed. The homogeneous solution was then poured into a square PTFE mold. The samples could be removed from the mold after 2 hours, and the final mechanical properties of the materials were obtained after 24 hours of curing at room temperature.

[0093] Samples crosslinked with BMI-689 were prepared by simply mixing the functionalized oil with BMI-689 for at least 24 h at room temperature.

[0094] Comparative example A 3-Furoic acid was mixed directly with epoxidized soybean oil in a 1:1 molar ratio to the epoxy rings of epoxidized soybean oil. The reaction was carried out under N2 atmosphere with magnetic stirring without solvent. The functionalization was carried out at 120°C overnight. The resulting furan-functionalized epoxidized soybean oil (FAcSO) was used in the next step without any further purification.

[0095] Furan-functionalized epoxidized soybean oil (FAcSO) was mixed with BMI-689 bismaleimide in a ratio of 70 wt.% furan-functionalized epoxidized soybean oil and 30 wt.% BMI-689. The mixture was allowed to react at room temperature for 2 days. After the reaction, the mixture became a solid elastic material.

[0096] Comparative example B Furfuryl alcohol (FA) was mixed with succinic anhydride (SA) in a 1:1 molar ratio to the anhydride. The reaction was carried out at 50° C. overnight at ambient conditions. The resulting succinated furfuryl alcohol (sFA) was used in the next step without any further purification.

[0097] Succinated furfuryl alcohol (sFA) was mixed with epoxidized soybean oil in a 1:1 ratio relative to the epoxy rings of the oil. The mixture was reacted overnight at 120 °C under N2 atmosphere with magnetic stirring without solvent. The resulting furan-functionalized epoxidized soybean oil (sFASO) was used in the next step without any further purification.

[0098] The resulting furan-functionalized epoxidized soybean oil (sFASO) was crosslinked using two different bismaleimides: 1,1′-(methylenedi-4,1-phenylene) bismaleimide (DPBM) and (BMI-689) bismaleimide.

[0099] To prepare the DPBM crosslinked network, sFASO was mixed with DPBM in a 1:1 molar ratio of furan to maleimide groups. The mixture was reacted at 150 °C with stirring and poured into a mold. After cooling, the material became an elastic solid.

[0100] To prepare the BMI-689 crosslinked network, sFASO was mixed with bismaleimide in the ratio of 70 wt.% furan-functionalized epoxidized soybean oil and 30 wt.% BMI-689. The mixture was allowed to react at room temperature for 2 days. After the reaction, the mixture became a solid elastic material.

[0101] Mechanical properties and self-repair efficiency A comparison of the mechanical properties and self-healing efficiency of the 12 different materials prepared in Example 7 is shown in Table 1. These materials were synthesized using three different cyclic anhydrides (maleic acid, itaconic acid, and succinic acid), crosslinked with two different bismaleimides (DPBM and BMI-689), and with three different furan / maleimide stoichiometric ratios.

[0102] [Table 1] Sample Ultimate tensile strength(MPa) No network formation Elongation at break (%) Self-healing condition 80℃, 30min 80℃, 30min Room temperature, 24 hours RT 24h ηUltimate tensile strength(%) ηElongation at break(%)

[0103] Fabrication of a soft robotic gripper The soft robotic gripper was fabricated by mold casting of the self-healing material. The mold was 3D printed using a Prusa SL1 stereolithography (SLA) printer with 3DM-HTR140 resin. The gripper is made up of eight different parts, which were joined together using a soldering iron at 150 °C to apply localized heat to the joints. [Explanation of symbols]

[0104] Drawing translation Figure 3 Castor oil (CO) Figure 6 Stress / MPa Stress / MPa Strain / % Figure 7 Storage modulus G' (MPa) Loss modulus G'' (MPa) Loss modulus G'' (MPa) Temperature (℃) Temperature (℃) Elastic network Viscoelastic liquid Tan delta (Tan δ) Tan delta (Tan δ) Heat flow (W / g) Figure 8 Storage modulus G' (MPa) Loss modulus G'' (MPa) Loss modulus G'' (MPa) Temperature T (℃) Temperature T(℃) Phase angle δ (°) Phase angle δ(°) Total Heat flow (Normalized) (w / g) Temperature (℃) Temperature (℃) Exo down Downward heat Figure 9 Heat flow (Normalized) Q (W / g) Temperature T (℃) Temperature T(℃) Exo down Downward heat Figure 10 Stress / MPa Stress / MPa Strain / % Healing at RT immediate 1h 1 hour 24h 24 hours 7 days 30 min 3h 3 hours 48h 48 hours original Figure 11 Elongation at break (%) Self-healing efficiency (%) Original 1st rep. First reprocessing 2nd rep. Second reprocessing 3rd rep. 3rd rep. Ultimate tensile stress (Mpa)

Claims

1. 1. A Diels-Alder type polymer comprising the reaction product of polymaleimide monomer units and a furan-functionalized prepolymer, The furan-functionalized prepolymer comprises a central moiety according to formula (I). 【Chemistry 1】 (In the formula, R 1 is -H), wherein at least one furan-functionalized side chain is attached to said central moiety, and said prepolymer backbone is polyester-based.

2. The furan-functionalized side chains are directly attached to the central moiety and have a structure according to formula (II). 【Chemistry 2】 (In the formula, A is -C 1～6 Alkyl-, -C 2～6 Alkenyl- and -C 1～6 alkyl-O-, 1～6 Alkyl-, -C 2～6 Alkenyl- and -C 1～6 Each alkyl-O- is optionally and independently selected from -halo, -OH, -C 1～6 Alkyl, -C 1～6 Alkenyl, and -OC 1～6 substituted with 1 to 3 substituents selected from alkyl; B is selected from -C(O)O- and -O(O)C-; k is an integer selected from 0, 1, and 2; l is an integer selected from 0 and 1; 2. The Diels-Alder type polymer of claim 1, wherein m is an integer selected from 0, 1, 2, 3, 4, and 5.

3. 3. The Diels-Alder type polymer of claim 1, wherein the central moiety of formula (I) is directly attached to the prepolymer backbone.

4. The central part of formula (I) is a linker structure according to formula (III) 【Chemistry 3】 (In the formula, X is -C 1～6 Alkyl- and -C 2～6 alkenyl-, wherein -C 1～6 Alkyl- and -C 2～6 Each alkenyl- is optionally and independently selected from -halo, -OH, -C 1～6 Alkyl, -C 1～6 Alkenyl and -OC 1～6 substituted with 1 to 3 substituents selected from alkyl; Y is selected from -C(O)O- and -O(O)C-; Z is selected from -O- and -C(O)O-; a is an integer selected from 0, 1, and 2; 4. The Diels-Alder type polymer of claim 3, wherein b is an integer selected from 0 and 1 and is attached to the prepolymer backbone via a tert-butyl ether.

5. The Diels-Alder type polymer according to any one of claims 1 to 4, wherein both the polymaleimide monomer unit and the furan-functionalized prepolymer have a functionality of at least 2, and the sum of the functionality of both the polymaleimide monomer unit and the furan-functionalized prepolymer is at least 4.

6. (Multi-Multi)

6. The Diels-Alder type polymer according to any one of claims 1 to 4, wherein the stoichiometric ratio of maleimide to furan between the polymaleimide monomer unit and the furan-functionalized prepolymer ranges from 1 to 0.

25.

7. The Diels-Alder type polymer according to any one of claims 1 to 4, wherein the stoichiometric ratio of maleimide to furan between the polymaleimide monomer unit and the furan-functionalized prepolymer is in the range of 1 to 0.

6. (Multi-Multi)

8. The Diels-Alder type polymer according to any one of claims 1 to 7, wherein the polymaleimide is selected from the list comprising 1,1'-(methylenedi-4,1-phenylene)bismaleimide, N,N'-(1,4-phenylene)dimaleimide, N,N'-(1,3-phenylene)dimaleimide and bismaleimide. (Multi-Multi)

9. A composition comprising the polymer according to any one of claims 1 to 8. (Multi-Multi)

10. 10. The composition of claim 9, further comprising a radical scavenger.

11. 11. The composition of claim 10, wherein the radical scavenger is selected from the list comprising hydroquinone butylated hydroxytoluene, 4-tert-butylcatechol, methyl-p-benzoquinone.

12. A method for producing a Diels-Alder type polymer, comprising the steps of preparing a composition comprising a polymaleimide monomer unit as defined in any one of claims 1 to 4 and a furan-functionalized prepolymer.

13. Use of the Diels-Alder type polymer according to any one of claims 1 to 8 or the composition according to any one of claims 9 to 11 as a self-repairing material. (Multi-Multi)

14. Use of a Diels-Alder type polymer according to any one of claims 1 to 8 or a composition according to any one of claims 9 to 11 in robotics or biomedicine. (Multi-Multi)

15. Use of a Diels-Alder type polymer according to any one of claims 1 to 8 or a composition according to any one of claims 9 to 11 in the manufacture of a 1D, 2D or 3D structure. (Multi-Multi)

16. Use of a Diels-Alder type polymer according to any one of claims 1 to 8 or a composition according to any one of claims 9 to 11 in the manufacture of a robot component. (Multi-Multi)

17. Use of a Diels-Alder type polymer according to any one of claims 1 to 8 or a composition according to any one of claims 9 to 11 in a manufacturing process selected from the list comprising filament extrusion, extrusion-based printing techniques, selective laser sintering, injection molding, compression molding, cast molding, soft lithography. (Multi-Multi)

18. 18. The use according to claim 17, wherein the extrusion-based printing technique is selected from the list comprising: fused filament printing, direct ink writing.

19. A 1D, 2D or 3D structure comprising a Diels-Alder type polymer according to any one of claims 1 to 8 or a composition according to any one of claims 9 to 11. (Multi-Multi)

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