Self-healing polymers

Abstract

The present invention generally relates to the field of polymers, in particular to self-healing polymers, and provides novel self-healing polymers and uses thereof in various domains, such as manufacturing of tires and robotics. Furthermore, the present invention relates to a method for preparing said self-healing polymers, and to structures comprising said polymers. In particular, the present invention provides pneumatic vehicle tires comprising the self-healing polymers.

Description

[0001] SELF-HEALING POLYMERS

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to the field of polymers, in particular to self-healing polymers, and provides novel self-healing polymers and uses thereof in various domains, such as manufacturing of tires and robotics. Furthermore, the present invention relates to a method for preparing said self-healing polymers, and to structures comprising said polymers. In particular, the present invention provides pneumatic vehicle tires comprising the self-healing polymers.

[0004] BACKGROUND TO THE INVENTION

[0005] In the field of robotics, more specifically in the application of soft grippers, it has been proven beneficial to use self-healing materials capable of healing a certain amount of damage sustained during its use. Soft grippers can for instance be used for fruit and vegetable picking, where the soft grippers come in close contact with sharp objects (e.g. sharp twigs, thorns, plastic or glass). As a result, macroscopic damage (e.g. perforations, cuts and ruptures) occurs over time and negatively impacts the performance of these grippers. Robots are also used in remote applications, like search-and-recovery or environmental investigations in (aero)space or marine environments, where it becomes difficult to repair or replace a damaged part.

[0006] Self-healing materials already exist today and have the ability to repair damage without the need to replace these materials. Depending on the type of self-healing material, the damage can be repaired with or without application of an external stimulus such as heat, pH changes, and light. To obtain a self-healing material, exchangeable dynamic bonds are typically introduced into polymer networks. In response to one or more external stimuli, the dynamic bonds creating crosslinks in the polymer network are able to shuffle, which permits the network to (be) reshape(d), preferably back to its original form. Ideally these materials possess the malleability of thermoplastics and the dimensional stability of thermosets, thereby providing a unique combination of physical properties, such as self-healing and improved recyclability.

[0007] CN109354829 and CN109354830 describe preparation methods for a self-repairing epoxy resin used for electrical insulation, using bisphenol A diglycidyl ether, furfuryl glycidyl ether and furfurylamine FA as raw materials for synthesizing a prepolymer with a furan ring as a side group and a terminal group, and reacting the prepolymer with N,N'-(4,4'-methylenediphenyl) bismaleimide BMI to form a reversible three-dimensional network.

[0008] WO2023213632 describes a preparation method for a Diels-Alder-based polymer, comprising the step of preparing a composition of a polymaleimide monomeric unit and a furan-functionalized prepolymer, wherein the furan-functionalized prepolymer is characterized in having a prepolymer backbone comprising a substituent having a central moiety according to the following formula

[0009]

[0010] wherein R1is -H; wherein at least one furan-functionalized sidechain is connected to said central moiety; and wherein said prepolymer backbone is based on a polyester.

[0011] Self-sealing pneumatic tires are known, and typically use butylrubber based sealants that line the inside of the tire. When the tire is punctured, for instance by a nail or screw, the sealant blocks the puncture in the tire tread, thereby preventing air from escaping. These self-sealing tires, however, have several disadvantages. Butylrubber based sealants are difficult to apply consistently, which may lead to air pockets and unbalanced tires. The effectiveness of these sealants can moreover diminish over time, for instance due to fluctuating temperature conditions. A further disadvantage of self-sealing tires having butylrubber based sealants, is that the tire still needs to be repaired or replaced, and that repairing such a self-sealing tire can be more complicated than repairing a regular tire due to the presence of the sealant material.

[0012] It is therefore an object of the current invention to address the problems associated with self-healing polymers known in the art, by providing novel self-healing polymers. It is furthermore an object of the current invention to address the problems associated with self-sealing tires known in the art.

[0013] SUMMARY OF THE INVENTION

[0014] In a first aspect, the present invention provides a method for preparing a self-healing polymer, wherein the method comprises the steps of:

[0015] a) reacting a mixture comprising at least one mono-epoxy compound, at least one bisepoxy compound, furfuryl amine, and optionally one or more further amines, at a first reaction temperature of at least 30 °C, thereby obtaining a reaction mixture comprising a furan-functionalized prepolymer; and

[0016] b) reacting the furan-functionalized prepolymer obtained in step a) with at least one polymaleimide at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer;

[0017] wherein the at least one mono-epoxy compound is represented by formula (I)

[0018]

[0019] wherein

[0020] Ri is selected from -Ci alkyl, -Cz-isalkenyl, -Cz-isalkynyl, and aryl; wherein each of said - Ci walkyl, -Cz-isalkenyl, -Cz- alkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents; and

[0021] wherein the at least one bis-epoxy compound is represented by formula (II)

[0022]

[0023] wherein

[0024] m is 1 , or an integer from 2 to 100; and

[0025] Ai is selected from -Ci walkylene-, and -Cz-izalkenylene-.

[0026] According to an embodiment, the present invention provides the method as defined herein, wherein the molar ratio of epoxy functionality of the total amount of the bis-epoxy compounds, relative to the total amount of the mono-epoxy compounds, is from 1 to 6.5, preferably from 1 .5 to 3.5, more preferably from 1 .7 to 2.9.

[0027] According to a further embodiment, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound is independently selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether.

[0028] According to a further embodiment, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound is C12-C14 alcohol glycidyl ether.

[0029] According to a further embodiment, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound is C12-C14 alcohol glycidyl ether.

[0030] According to a further embodiment, the present invention provides the method as defined herein, wherein the at least one polymaleimide is a bismaleimide represented by formula (IV)

[0031]

[0032] wherein Xi is selected from -Ci alkylene-, -C2-isalkenylene-, -C2-isalkynylene-, aryl, and any combination of two or more thereof; wherein each of said -Ci- alkylene-, -C2-isalkenylene-, -C2-isalkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

[0033] According to a further embodiment, the present invention provides the method as defined herein, wherein the at least one polymaleimide is a bismaleimide selected from 1 ,1 ’-(methylenedi-4,1-phenylene)bismaleimide, N,N’-(1 ,3-phenylene)bismaleimide, N,N’-(4-methyl-1 ,3-phenylene)-bismaleimide, 4,4'-bis(maleimidophenyl) ether, N,N'-Bismaleimido-1 ,2-ethane, N,N'-Bismaleimido-1 ,3-propane, N,N'-Bismaleimido-1 ,4-butane, N,N'-Bismaleimido-1 ,5-pentane, N,N'-Bismaleimido-1 ,6-hexane, N,N'-Bismaleimido-1 ,9-nonane, N,N'-Bismaleimido-1 ,10-decane, N,N'-Bismaleimido-1 ,12-dodecane, and N,N'-Bismaleimido-2-methyl-1 ,3-propane. According to a further embodiment, the present invention provides the method as defined herein, wherein the molar ratio of maleimide functionality of the at least one polymaleimide, relative to furan functionality of the furan-functionalized prepolymer, reacted in step b), is from 0.05 to 0.95, preferably from 0.10 to 0.80, more preferably from 0.15 to 0.65, even more preferably from 0.20 to 0.55, yet even more preferably from 0.25 to 0.50, yet even more preferably from 0.30 to 0.40.

[0034] According to a further embodiment, the present invention provides the method as defined herein, comprising the further step of reacting the furan-functionalized prepolymer obtained in step a) with boric acid, thereby obtaining a partially crosslinked furan-functionalized prepolymer; and wherein in step b), the partially crosslinked furan-functionalized prepolymer is reacted with the at least one polymaleimide at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer.

[0035] In a further aspect, the present invention provides a self-healing polymer obtainable by the method as defined herein.

[0036] In yet a further aspect, the present invention provides a self-healing polymer comprising the Diels-Alder reaction product of a furan-functionalized prepolymer and at least one polymaleimide;

[0037] wherein the furan-functionalized prepolymer is represented by formula (III)

[0038]

[0039] wherein

[0040] n is an integer from 2 to 100;

[0041] m is 1 , or an integer from 2 to 100;

[0042] A1 is selected from -Ci-walkylene-, and -C2-walkenylene-; and

[0043] R1 is selected from -Ci-isalkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl; wherein each of said -Ci-isalkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents; and

[0044] wherein the at least one polymaleimide is a bismaleimide represented by formula (IV)

[0045]

[0046] wherein

[0047] Xi is selected from -Ci alkylene-, -C2-isalkenylene-, -C2-isalkynylene-, aryl, and any combination of two or more thereof; wherein each of said -Ci- alkylene-, -C2- isalkenylene-, -C2-isalkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

[0048] According to a further embodiment, the present invention provides the self-healing polymer as defined herein, wherein the average molecular weight of the furan-functionalized prepolymer, based on the stoichiometry of the reagents used, is from 2500 to 10 000 g / mol, preferably from 3500 to 6000 g / mol.

[0049] According to a further embodiment, the present invention provides the self-healing polymer as defined herein, wherein the weight average molecular weight Mw of the furan-functionalized prepolymer, as determined by GPC, is from 2500 to 10000 g / mol, preferably from 3500 to 9000 g / mol, more preferably from 4500 to 8000 g / mol, even more preferably from 5000 to 7500 g / mol.

[0050] According to a further embodiment, the present invention provides the self-healing polymer as defined herein, wherein the furan-functionalized prepolymer is a partially crosslinked furan-functionalized prepolymer obtained by reacting the furan-functionalized prepolymer with boric acid.

[0051] In yet a further aspect, the present invention provides a use of the self-healing polymer as defined herein, in the manufacturing of 1 D, 2D or 3D structures, in particular in the manufacturing of pneumatic tires. In yet a further aspect, the present invention provides a 1 D, 2D, or 3D structure comprising the self-healing polymer as defined herein, in particular a pneumatic tire comprising the self-healing polymer as defined herein.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] With specific reference now to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in the cause of providing what is believed to be the most useful and readily description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description provided with the drawings makes apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0054] Figures 1A-1 J, also abbreviated as FIG. 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, 1G, 1 H, 11 and 1 J, respectively, provide a representation of the results of dynamic puncture test performed on tires coated with self-healing polymers prepared according to examples 8a, 8b, 8c, 8i, 8j, 8k, 8I, 8m, 8o and 8p, respectively.

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056] The present invention will now be further described. In the following paragraphs, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0057] When describing the compounds of the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise:

[0058] The term "alkyl" by itself or as part of another substituent refers to a fully saturated hydrocarbon of Formula CxHzx+i wherein x is a number greater than or equal to 1 . Generally, alkyl groups of this invention comprise from 1 to 20 carbon atoms. Alkyl groups may be linear or branched and may be substituted as indicated herein. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, Ci-4alkyl means an alkyl of one to four 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, undecyl and its isomers, dodecyl and its isomers, tridecyl and its isomers, tetradecyl and its isomers, pentadecyl and its isomers, hexadecyl and its isomers, heptadecyl and its isomers, octadecyl and its isomers, nonadecyl and its isomers, eicosanyl and its isomers. The term "optionally substituted alkyl" refers to an alkyl group optionally substituted with one or more substituents (for example 1 to 4 substituents, for example 1 , 2, 3, or 4 substituents) at any available point of attachment.

[0059] Whenever the term “substituted” is used in the present invention, it is meant to indicate that one or more hydrogens on the atom indicated in the expression using “substituted” is replaced with a selection from the indicated group, provided that the indicated atom’s normal valency is not exceeded, and that the substitution results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into a therapeutic agent.

[0060] Where groups may be optionally substituted, such groups may be substituted once or more, and preferably once, twice or thrice. Non-limiting examples of such substituents are selected from halogen (-halo), hydroxy (-OH), oxo (=0), nitro (-NO2), amino (-NR’R”), cyano (-CN), alkyl, cycloalkyl, alkenyl, alkynyl, alkoxy or aryloxy (-OR’”), aryl, heteroaryl, carbonyl (-C(O)Riv), carboxyl (-COOH), ester or alkoxycarbonyl (-C(O)ORV), ester or alkylcarbonyloxy (-OC(O)Rvi), amido or aminocarbonyl (-NR’C(O)), amido or carbonylamino (-C(O)NR’), heterocyclyl, carbonyl, acyl, arylcarbonyl, thio (-SH), alkylthio (-SRvi), and the like.

[0061] The term "alkenyl" or “alkene”, as used herein, unless otherwise indicated, means straight-chain, cyclic, or branched-chain hydrocarbon radicals containing at least one carbon-carbon double bond. Examples of alkenyl radicals include ethenyl, E- and Z-propenyl, 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, be it in the terminal or internal positions, and the like. Generally alkenyl or alkene moieties of the present invention comprise from 2 to 20 C atoms. An optionally substituted alkenyl refers to an alkenyl having optionally one or more substituents (for example 1 , 2, 3 or 4), selected from those defined above for substituted alkyl. Unless stated otherwise, when a reference to "alkenyl" or “alkene”, it refers to all possible isomers of each of the carbon-carbon double bonds present.

[0062] The term "alkynyl", as used herein, unless otherwise indicated, means straight-chain or branched-chain hydrocarbon radicals containing at least one carbon-carbon triple bond. Examples of alkynyl radicals include ethynyl, propynyl, butynyl, pentynyl, hexynyl, hexadiynyl, be it in the terminal or internal positions, and the like. An optionally substituted alkynyl refers to an alkynyl having optionally one or more substituents (for example 1 , 2, 3 or 4), selected from those defined above for substituted alkyl.

[0063] In the context of the present invention, the alkyl, alkenyl and alkynyl moieties as defined herein may also further comprise one or more heteroatoms, such as selected from N, S or O, in that for example a carbon atom in an alkyl, alkene or alkyne chain is replaced by a heteroatom. When two or more C atoms are replaced by heteroatoms, the heteroatoms may be adjacent or separated, as long as it results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into a therapeutic agent. An example of a stable combination of two adjacent heteroatoms is a disulfide (-S-S-) group. Where a carbon atom in an alkyl, alkenyl or alkynyl chain is replaced by an N atom, the N atom may be N or NH depending on the number of bonds connected to said C atom.

[0064] The term “cycloalkyl” by itself or as part of another substituent is a cyclic alkyl group, that is to say, a monovalent, saturated, or unsaturated hydrocarbyl group having 1 , 2, or 3 cyclic structure. Cycloalkyl includes all saturated or partially saturated (containing 1 or 2 double bonds) hydrocarbon groups containing 1 to 3 rings, including monocyclic, bicyclic, or polycyclic alkyl groups. Cycloalkyl groups may comprise 3 or more carbon atoms in the ring and generally, according to this invention comprise from 3 to 15 atoms. Examples of cycloalkyl groups include but are not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, adamantanyl and cyclodecyl. An “optionally substituted cycloalkyl” refers to a cycloalkyl having optionally one or more substituents (for example 1 to 3 substituents, for example 1 , 2, 3 or 4 substituents), selected from those defined above for substituted alkyl.

[0065] Where alkyl groups as defined are divalent, i.e., with two single bonds for attachment to two other groups, they are termed "alkylene" groups. Non-limiting examples of alkylene groups includes methylene, ethylene, methylmethylene, trimethylene, propylene, tetramethylene, ethylethylene, 1 ,2-dimethylethylene, pentamethylene and hexamethylene. Similarly, where alkenyl groups as defined above and alkynyl groups as defined above, respectively, are divalent radicals having single bonds for attachment to two other groups, they are termed "alkenylene" and "alkynylene" respectively.

[0066] The term “alkoxy" or “alkyloxy” as used herein refers to a radical having the Formula -OR’” wherein R’” is alkyl, alkenyl, or alkynyl. Non-limiting examples of suitable alkoxy include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and hexyloxy. The term “aryloxy" as used herein refers to a radical having the Formula -OR’” wherein R’” is aryl.

[0067] Where the oxygen atom in an alkoxy group is substituted with sulfur, the resultant radical is referred to as alkylthio or arylthio, such as methylthio, ethylthio, phenylthio, and the like.

[0068] The term “oxo” as used herein refers to the group =0.

[0069] The term "carbonyl" by itself or as part of another substituent refers to the group -C(O)Riv, wherein Rivis a hydrogen atom (i.e. an aldehyde), or alkyl, alkenyl, alkynyl or aryl (i.e. a ketone).

[0070] The term "carboxy" or “carboxyl” or “hydroxycarbonyl” by itself or as part of another substituent refers to the group -COOH, -C(O)OH, or -CO2H.

[0071] The term "alkoxycarbonyl" by itself or as part of another substituent refers to a carboxy group linked to an alkyl radical i.e. to form -C(O)ORV, wherein Rvis alkyl, alkenyl, alkynyl or aryl.

[0072] The term “alkylcarbonyloxy” by itself or as part of another substituent refers to a -OC(O)Rviwherein Rviis alkyl, alkenyl, alkynyl or aryl.

[0073] The term "heterocycle" as used herein by itself or as part of another group refers to nonaromatic, fully saturated or partially unsaturated cyclic groups (for example, 3 to 13 member monocyclic, 7 to 17 member bicyclic, or 10 to 20 member tricyclic ring systems, or containing a total of 3 to 10 ring atoms) which have at least one heteroatom in at least one carbon atomcontaining ring. Each ring of the heterocyclic group containing a heteroatom may have 1 , 2, 3 or 4 heteroatoms selected from nitrogen atoms, oxygen atoms and / or sulfur atoms, where the nitrogen and sulfur heteroatoms may optionally be oxidized and the nitrogen heteroatoms may optionally be quaternized. The heterocyclic group may be attached at any heteroatom or carbon atom of the ring or ring system, where valence allows. The rings of multi-ring heterocycles may be fused, bridged and / or joined through one or more spiro atoms. An optionally substituted heterocyclic refers to a heterocyclic having optionally one or more substituents (for example 1 to 4 substituents, or for example 1 , 2, 3 or 4), selected from those defined above for substituted alkyl. Non-limiting examples of heterocycle comprise: piperidinyl, azepanyl, morpholinyl.

[0074] The term “aryl" as used herein refers to a polyunsaturated, aromatic hydrocarbyl group having a single ring (i.e. phenyl) or multiple aromatic rings fused together (e.g. naphthalene or anthracene) or linked covalently, typically containing 6 to 10 atoms; wherein at least one ring is aromatic. The aromatic ring may optionally include one to three additional rings (either cycloalkyl, heterocyclyl, or heteroaryl) fused thereto. Aryl is also intended to include the partially hydrogenated derivatives of the carbocyclic systems enumerated herein. Non-limiting examples of aryl comprise phenyl, napthyl, and the like. The aryl group or heterocycle as defined herein can optionally be substituted by one or more substituents (for example 1 to 5 substituents, for example 1 , 2, 3, 4 or 5) at any available point of attachment. Non-limiting examples of such substituents are selected from halogen, hydroxyl, oxo, nitro, amino, hydrazine, aminocarbonyl, azido, cyano, alkyl, cycloalkyl, alkenyl, alkynyl, cycloalkylalkyl, alkylamino, alkoxy, -SO2-NH2, aryl, heteroaryl, aralkyl, haloalkyl, haloalkoxy, alkoxycarbonyl, alkylaminocarbonyl, heteroarylalkyl, alkylsulfonamide, heterocyclyl, alkylcarbonylaminoalkyl, aryloxy, alkylcarbonyl, acyl, arylcarbonyl, aminocarbonyl, alkylsulfoxide, -SO2RX, alkylthio, carboxyl, and the like, wherein Rxis alkyl or cycloalkyl.

[0075] The term “heteroaryl” as used herein by itself or as part of another group refers but is not limited to 5 to 12 carbon-atom aromatic rings or ring systems containing 1 to 3 rings which are fused together or linked covalently, typically containing 5 to 8 atoms; at least one of which is aromatic in which one or more carbon atoms in one or more of these rings can be replaced by oxygen, nitrogen or sulfur atoms where the nitrogen and sulfur heteroatoms may optionally be oxidized and the nitrogen heteroatoms may optionally be quaternized. Such rings may be fused to an aryl, cycloalkyl, heteroaryl or heterocyclyl ring. Non-limiting examples of such heteroaryl, include piridinyl, azepinyl.

[0076] An “optionally substituted heteroaryl” refers to a heteroaryl having optionally one or more substituents (for example 1 to 4 substituents, for example 1 , 2, 3 or 4), selected from those defined above for substituted aryl.

[0077] As used herein the terms such as “alkyl, aryl, or cycloalkyl, each being optionally substituted with” or “alkyl, aryl, or cycloalkyl, optionally substituted with” refers to optionally substituted alkyl, optionally substituted aryl and optionally substituted cycloalkyl.

[0078] The term “halo” or “halogen” as a group or part of a group is generic for fluoro, chloro, bromo, or iodo.

[0079] The term "direct bond" as used herein, refers to a chemical linkage directly connecting two or more specified moieties, without the presence of any intervening elements or groups

[0080] As used in the specification and 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 terms described above, and others used in the specification are well understood to those in the art.

[0081] As stated hereinbefore, according to a first aspect, the present invention provides a method for preparing a self-healing polymer, the method comprising the steps of:

[0082] a) reacting a mixture comprising at least one mono-epoxy compound, at least one bisepoxy compound, furfuryl amine, and optionally one or more further amines, at a first reaction temperature of at least 30 °C, thereby obtaining a reaction mixture comprising a furan-functionalized prepolymer; and

[0083] b) reacting the furan-functionalized prepolymer obtained in step a) with at least one polymaleimide at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer.

[0084] It was found that self-healing polymers can be readily prepared by the method as defined herein. An advantage of the current method is that furfurylamine is used to introduce a furan functionality into the prepolymer, whereas the presence of a furan functionality is essential to react with the maleimide functionality of the at least one polymaleimide via a Diels-Alder reaction.

[0085] Furfurylamine (herein abbreviated as ‘FA’ or ‘Fur-NHz’) is typically prepared in one step by the reductive amination of furfural, whereas furfural is produced from hemicellulose present in lignocellulosic biomass. Furfurylamine is therefore a relatively cheap reagent which is readily available in large quantities, and moreover biobased for the most part. In contrast, furan glycidyl ether, a reagent often used to introduce a furan functionality into polymers, is typically prepared in a multi-step process. In this multi-step process, furfural is hydrogenated first to furfuryl alcohol, followed by reaction of furfuryl alcohol with epichlorohydrin and finally ring-closure by reaction with a base. Due to this multi-step process needed to prepare it, furan glycidyl ether is more expensive than furfurylamine, and is only available in relatively small quantities.

[0086] A further advantage of the method as defined herein, is that the reaction of furfurylamine with the mono-epoxy and / or bis-epoxy compounds provides hydroxy functionalities, which can be used for further functionalization of the furan-functionalized prepolymer and / or the self-healing polymer. The hydroxy functionalities can for instance be used for crosslinking the furan-functionalized pre-polymer, as will be described later.

[0087] The method as defined herein has the further advantage that self-healing polymers can be prepared relatively fast, compared to methods known in the art, even within a timeframe of 4 hours or less.

[0088] It is a further advantage of the method as defined herein, that the combination of at least one mono-epoxy compound and at least one bis-epoxy compound, in the reaction mixture, improves control over the average molecular weight and functionality of the prepolymer, allowing to tune the chemical and mechanical properties of the self-healing polymers.

[0089] It was further found that the method as defined herein allows to tailor the properties of the self-healing polymer for different applications. In the context of the present invention, the term ‘(a) mono-epoxy compound(s) refers to (a) chemically defined compound(s) having one epoxide or oxirane moiety, in particular one glycidyl ether moiety, and may be represented by formula (A)

[0090]

[0091] wherein

[0092] R is selected from any substituted or unsubstituted alkyl, any substituted or unsubstituted alkenyl, any substituted or unsubstituted alkynyl, any substituted or unsubstituted aryl, any oligomer, or any polymer.

[0093] In step a) of the method as defined herein, the mixture comprises at least one mono-epoxy compound, and optionally one or more further mono-epoxy compounds. The mixture in step a) may therefore comprise one, two, three, four, five, or more different mono-epoxy compounds, wherein the term ‘different’ refers to different chemical structures. When the mixture in step a) comprises two or more different mono-epoxy compounds, they may be added separately to the mixture or as a pre-defined mixture of mono-epoxy compounds. An example of a pre-defined mixture of mono-epoxy compounds is C12-14 alcohol glycidyl ether, which is a mixture of mainly 12 and 14 carbon chain alcohols that have been glycidated.

[0094] It is however preferred that the mixture in step a) comprises only one mono-epoxy compound, as this may provide a furan-functionalized prepolymer with a lower polydispersity and / or may provide a self-healing polymer with improved properties. Therefore, in embodiments, the present invention provides the method as defined herein, wherein in step a) the mixture comprises only one mono-epoxy compound, wherein the mono-epoxy compound is as defined herein.

[0095] It was found that particular mono-epoxy compounds are preferred, as this may provide a self-healing polymer with improved properties. Therefore, in embodiments, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound, and optionally the one or more further mono-epoxy compounds, are represented by formula (I)

[0096]

[0097] wherein

[0098] Ri is selected from -Ci-isalkyl, -Cz-isalkenyl, -Cz-isalkynyl, and aryl; wherein each of said - Ci-isalkyl, -Cz-isalkenyl, -Cz-isalkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents. In useful embodiments, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound, and optionally the one or more further mono-epoxy compounds, are represented by formula (I)

[0099]

[0100] wherein

[0101] Ri is selected from -Ci-isalkyl, and aryl.

[0102] In particular embodiments, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound, and optionally the one or more further mono-epoxy compounds, are independently selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether.

[0103] In particular embodiments, the present invention provides the method as defined herein, wherein the at least one mono-epoxy compound is C12-C14 alcohol glycidyl ether.

[0104] Similarly, in the context of the present invention, the term ‘(a) bis-epoxy compound(s)’ refers to (a) chemically defined compound(s) having two epoxide or oxirane moieties, in particular two glycidyl ether moieties, and may be represented by formula (B)

[0105]

[0106] wherein

[0107] A is selected from any substituted or unsubstituted alkylene, any substituted or unsubstituted alkenylene, any substituted or unsubstituted alkynylene, any substituted or unsubstituted aryl, any oligomer, or any polymer.

[0108] In step a) of the method as defined herein, the mixture comprises at least one bis-epoxy compound, and optionally one or more further bis-epoxy compounds. The mixture in step a) may therefore comprise one, two, three, four, five, or more different bis-epoxy compounds, wherein the term ‘different’ refers to different chemical structures. When the mixture in step a) comprises two or more different bis-epoxy compounds, they may be added separately to the mixture or as a pre-defined mixture of bis-epoxy compounds.

[0109] It is however preferred that the mixture in step a) comprises only one bis-epoxy compound, as this may provide a furan-functionalized prepolymer with a lower polydispersity and / or may provide a self-healing polymer with improved properties. Therefore, in embodiments, the present invention provides the method as defined herein, wherein in step a) the mixture comprises only one bis-epoxy compound, and wherein the bis-epoxy compound is as defined herein.

[0110] It was also found that particular bis-epoxy compounds are preferred, as this may provide a self-healing polymer with improved properties. Therefore, in embodiments, the present invention provides the method as defined herein, wherein the at least one bis-epoxy compound, and optionally the one or more further bis-epoxy compounds, are represented by formula (II) < >

[0111]

[0112] wherein

[0113] m is 1 , or an integer from 2 to 100; and

[0114] Ai is selected from -Ci-i2alkylene-, and -C2-i2alkenylene-.

[0115] It is an advantage of the method as defined herein, that by using (an) aliphatic bis-epoxy compound(s), the resulting self-healing polymers may have self-healing properties at ambient or sub-ambient temperatures. Self-healing at ambient or sub-ambient temperatures is important for self-healing tires, such as car tires or bicycle tires.

[0116] In useful embodiments, the present invention provides the method as defined herein, wherein m is an integer from 2 to 50, preferably from 3 to 40, more preferably from 4 to 30, even more preferably from 5 to 20, yet even more preferably from 6 to 15, most preferably m is an integer from 7 to 12.

[0117] In particular embodiments, the present invention provides the method as defined herein, wherein the at least one bis-epoxy compound, and optionally the one or more further bis-epoxy compounds, are selected from 1 ,3-propanediol diglycidyl ether, 1 ,4-butanediol diglycidyl ether, 1 ,5-pentanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1 ,6-hexanediol diglycidyl ether, and 1 ,10-decanediol diglycidyl ether.

[0118] In particular embodiments, the present invention provides the method as defined herein, wherein the at least one bis-epoxy compound, and optionally the one or more further bis-epoxy compounds, are selected from polyethyleneglycol diglycidyl ether, polypropyleneglycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether.

[0119] In step a) of the method as defined herein, the amine functionality of the furfurylamine, and optionally the one or more further amines, reacts with the oxirane functionality of the monoepoxy compounds and / or bis-epoxy compounds, thereby providing a linear prepolymer having pendant furan (herein abbreviated as ‘Fur’) groups. Scheme 1 provides a schematic representation of the reaction taking place in step a) according to embodiments of the method as defined herein, wherein a mixture of at least one mono-epoxy compound (ME), at least one bis-epoxy compound (BE), and furfurylamine (FA) reacts to provide a furan-functionalized prepolymer (FFP), wherein R, n and A are as defined herein.

[0120]

[0121] FFP

[0122] Scheme 1

[0123] When one molecule of furfurylamine reacts with two molecules of a bis-epoxy compound, chain extension of the furan-functionalized prepolymer takes place, leading to two or more (n) structural units having a pendant furan group. When one molecule of furfurylamine reacts with one molecule of a bis-epoxy compound and one molecule of a mono-epoxy compound, polymerization is terminated, leading to an end-capped structural unit having a pendant furan group. Consequently, the hydroxy (OH) functionality of the furan-functionalized prepolymer is about two times the furan functionality.

[0124] The furan-functionalized prepolymer obtained in step a) according to embodiments of the method as defined herein, wherein no further primary amines are present, may be represented by formula (III)

[0125]

[0126] wherein

[0127] n is an integer from 2 to 100; and

[0128] m, A1, and R1 are as defined in any of the embodiments described herein.

[0129] In useful embodiments, the present invention provides the method as defined herein, wherein n is an integer from 2 to 50, preferably from 3 to 25, more preferably from 4 to 15, even more preferably n is an integer from 5 to 10.

[0130] In step a) of the method as defined herein, the mixture may comprise one or more further amines. By reacting the mono-epoxy compounds and the bis-epoxy compounds in the mixture with both furfurylamine and one or more further amines, the amount of pendant furan groups may be tailored. The one or more further amines can be any primary amine capable of reacting with the oxirane moiety of the mono-epoxy compounds and / or the bis-epoxy compounds. In the context of the present invention, the term ‘primary amine’ refers to a compound having at least one -NH2 group. In particular, the one or more further amines can be any primary monoamine, any primary diamine, any primary triamine, or any primary polyamine. In the context of the present invention, the term ‘primary monoamine’ refers to a compound having one -NH2 group, the term ‘primary diamine’ refers to a compound having two -NH2 groups, the term ‘primary triamine’ refers to a compound having three -NH2 groups, and the term ‘primary polyamine’ refers to a compound having at least two -NH2 groups. When at least one further amine is a primary polyamine, such as a primary diamine or a primary triamine, crosslinking of the prepolymer by the one or more further amines may occur. In contrast, when the one or more further amines are primary monoamines, crosslinking of the prepolymer by the one or more further amines does not occur. Preferably, the one or more further amines are primary monoamines.

[0131] The furan-functionalized prepolymer obtained in step a) according to embodiments of the method as defined herein, wherein in step a) at least one further amine is present, and wherein the least one further amine is a monoamine, may be represented by formula (Illa)

[0132]

[0133] wherein

[0134] each instance of Rais independently selected from -CHz-Fur, -Ci alkyl, -Cz-isalkenyl, -C2- isalkynyl, and aryl; wherein at least part of Rais -CHz-Fur; and

[0135] n, m, A1, and R1 are as defined in any of the embodiments described herein. It was further found that in step a) of the method as defined herein, a particular molar ratio of epoxy functionality of the total amount of the bis-epoxy compounds, relative to the total amount of the mono-epoxy compounds may provide improved control of the molecular weight of the furan-functionalized prepolymer. In a preferred embodiment, the present invention provides the method as defined herein, wherein the molar ratio of epoxy functionality of the total amount of the combined bis-epoxy compounds, relative to the total amount of the combined mono-epoxy compounds, is from 1 .0 to 6.5, preferably from 1 .2 to 5.0, more preferably from 1 .4 to 3.5, even more preferably from 1 .5 to 3.2, yet even more preferably from 1 .6 to 3.0, and most preferably from 1 .7 to 2.9.

[0136] Preferably, the molar ratio of furfuryl amine, relative to the total amount of mono-epoxy compounds and bis-epoxy compounds combined, is from 0.3 to 0.7, preferably from 0.35 to 0.65, even more preferably from 0.4 to 0.6, yet even more preferably from 0.42 to 0.58, yet even more preferably from 0.45 to 0.55, most preferably about 0.50.

[0137] In step a) of the method as defined herein, the furan-functionalized prepolymer can be obtained by reacting the mixture comprising the at least one mono-epoxy compound, the at least one bis-epoxy compound, the furfuryl amine, and optionally the one or more further amines, at any temperature of at least 30 °C. It is however preferred to react the mixture at a higher temperature than 30 °C to enhance the reaction kinetics. It is also preferred to react the mixture at a first reaction of at most 200 °C to avoid side-reactions. In a preferred embodiment, the present invention provides the method as defined herein, wherein the first reaction temperature is from 30 to 200 °C, preferably from 40 to 180 °C, more preferably from 50 to 160 °C, even more preferably from 60 to 140 °C, yet even more preferably from 70 to 120 °C.

[0138] In the context of the present invention, the term ‘polymaleimide(s)’ refers to (a) chemically defined compound(s) comprising two or more maleimide groups or functionalities, such as two, three, four, or more maleimide groups. In the context of the present invention, the term ‘bismaleimide’ refers to a compound having two maleimide functionalities, and the term ‘trismaleimide’ refers to a compound having three maleimide functionalities. A bismaleimide may be represented by formula (C)

[0139]

[0140] wherein

[0141] X is selected from any substituted or unsubstituted alkyl, any substituted or unsubstituted alkenyl, any substituted or unsubstituted alkynyl, any substituted or unsubstituted aryl, any oligomer, or any polymer.

[0142] In step b) of the method as defined herein, at least part of the furan groups or functionalities of the furan-functionalized prepolymer and at least part of the maleimide groups or functionalities of the polymaleimide react to form Diels-Alder bonds, thereby providing a crosslinked network, in particular a reversible crosslinked network.

[0143] As mentioned herein and unless provided otherwise, the terms “Diels-Alder bond(s)” or “DA bond(s)” refer to either isomer of the cycloadduct formed by a Diels-Alder reaction between a furan group and a maleimide group. The Diels-Alder reaction, forming the Diels-Alder bonds, is an equilibrium reaction making the formed crosslink bonds dynamic. Bonds are constantly broken and reformed in said dynamic network over time. Diels-Alder bonds are strong covalent bonds that can be thermally dissociated or mechanically broken and reformed in a reversible fashion, leading to self-healing characteristics. Consequently, the term “(a) Diels-Alder reaction product(s) of maleimide groups and furan groups” should be understood as the result of a Diels-Alder reaction between a furan group and a maleimide group.

[0144] Scheme 2 provides a schematic representation of a Diels-Alder reaction between a furan group A and maleimide group B resulting in a Diels-Alder reaction product C.

[0145]

[0146] Scheme 2

[0147] If Diels-Alder networks are damaged, Diels-Alder bonds and hydrogen bonding interactions are locally broken in a reversible fashion, resulting in active fracture surfaces. The hydrogen donors and acceptors and the newly formed furan and maleimide functional groups, resulting from the reversible mechanical breaking of the Diels-Alder bonds, autonomously reform the broken bonds, thus restoring the polymer network structure and related properties. To effectuate healing of this damaged area, a first step of the self-healing process entails bringing the fractured surfaces back into contact. Depending on the size of the damage, manual intervention or intervention by the robotic system might be necessary in order to actively push both fractured surfaces back together, for example when the material is cut all the way through, and two separate pieces are formed. Such full cuts require both fractured pieces to be pushed back together to initiate the healing process. In this case, it is of importance that both pieces are pushed back together as soon as possible after the damage occurred.

[0148] As used herein and unless provided otherwise, the term “self-healing efficiency” should be understood as the recovery of a material property (e.g. mechanical strength) and measured by the ratio of the measured property after healing to the initial material property, being the property before damage. Healing efficiencies are for example based on mechanical moduli, mechanical strength, characterized by fracture stresses and fracture strains. Said efficiency may be expressed in percentages.

[0149]

[0150] Scheme 3 Scheme 3 provides a schematic representation of the reaction taking place in step b) according to embodiments of the method as defined herein, wherein at least part of the furan groups or functionalities of the furan-functionalized prepolymer and at least part of the maleimide groups or functionalities of the polymaleimide react to form Diels-Alder bonds, thereby providing a crosslinked network, wherein n, R, A and X are as defined herein.

[0151] In step b) of the method as defined herein, the furan-functionalized prepolymer is reacted with at least one polymaleimide, and may therefore be reacted with one, two, three, or more different polymaleimides, wherein the term ‘different’ refers to different chemical structures. It is however preferred that the furan-functionalized prepolymer in step b) is reacted with only one polymaleimide, as this may provide a self-healing polymer with improved properties. Therefore, in embodiments, the present invention provides the method as defined herein, wherein in step b) the furan-functionalized prepolymer is reacted with only one polymaleimide, wherein the polymaleimide is as defined herein.

[0152] The at least one polymaleimide may be added to the furan-functionalized prepolymer, in particular to the reaction mixture comprising the furan-functionalized prepolymer, obtained in step a). When the furan-functionalized prepolymer in step b) is reacted with two or more different polymaleimides, they may be added separately to the furan-functionalized prepolymer, in particular to the reaction mixture comprising the furan-functionalized prepolymer, obtained in step a) or they may be added as a pre-defined mixture of polymaleimides. In particular embodiments, the present invention provides the method as defined herein, comprising the further step of adding at least one polymaleimide to the furan-functionalized prepolymer obtained in step a), before reacting the furan-functionalized prepolymer and the at least one polymaleimide in step b).

[0153] It was found that particular polymaleimides are preferred, as this may provide a self-healing polymer with improved properties. Therefore, in embodiments, the present invention provides the method as defined herein, wherein the at least one polymaleimide, and optionally the one or more further polymaleimides, are bismaleimides represented by formula (IV)

[0154]

[0155] wherein

[0156] Xi is selected from -Ci alkylene-, -Cz- alkenylene-, -Cz- alkynylene-, aryl, and any combination of two or more thereof; wherein each of said -Ci alkylene-, -Cz- alkenylene-, -C2-1 salkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

[0157] In useful embodiments, the present invention provides the method as defined herein, wherein the at least one polymaleimide, and optionally the one or more further polymaleimides, are bismaleimides represented by formula (IV)

[0158]

[0159] wherein

[0160] Xi is selected from -Ci-i2alkylene, -C2-i2alkenylene-, aryl, and any combination of two or more thereof; wherein each of said -Ci-i2alkylene-, -C2-i2alkenylene-, and aryl optionally comprises one or more substituents selected from -halo, -Ci ealkyl, and -O-Ci-ealkyl.

[0161] In particular embodiments, the present invention provides the method as defined herein, wherein the at least one polymaleimide, and optionally the one or more further polymaleimides, are bismaleimides selected from 1 ,1 ’-(methylenedi-4,1-phenylene)bismaleimide, N,N’-(1 ,3-phenylene)bismaleimide, N,N’-(4-methyl-1 ,3-phenylene)-bismaleimide, 4,4'-bis(maleimidophenyl) ether, N,N'-Bismaleimido-1 ,2-ethane, N,N'-Bismaleimido-1 ,3-propane, N,N'-Bismaleimido-1 ,4-butane, N,N'-Bismaleimido-1 ,5-pentane, N,N'-Bismaleimido-1 ,6-hexane, N,N'-Bismaleimido-1 ,9-nonane, N,N'-Bismaleimido-1 ,10-decane, N,N'-Bismaleimido-1 ,12-dodecane, and N,N'-Bismaleimido-2-methyl-1 ,3-propane.

[0162] It appeared that a particular maleimide-to-furan ratio may provide a self-healing polymer with improved properties. In the context of the present invention, the terms ‘maleimide-to-furan ratio’ or ‘r’ refer to the molar ratio of maleimide functionality of the at least one polymaleimide, relative to furan functionality of the furan-functionalized prepolymer, reacted in step b) of the method as defined herein. The maleimide-to-furan ratio r preferably is at least 0.05, such as at least 0.10, at least 0.15, at least 0.20, at least 0.25, at least 0.30, at least 0.35, at least 0.40, or at least O.45. The maleimide-to-furan ratio r preferably is at most 0.95, such as at most 0.90, at most 0.85, at most 0.80, at most 0.75, at most 0.70, at most 0.65, at most 0.60, at most 0.55, or at most 0.50. In a preferred embodiment, the present invention provides the method as defined herein, wherein the molar ratio of maleimide functionality of the at least one polymaleimide, relative to furan functionality of the furan-functionalized prepolymer, reacted in step b) of the method as defined herein, is from 0.05 to 0.95, preferably from 0.10 to 0.80, more preferably from 0.15 to 0.65, even more preferably from 0.20 to 0.55, yet even more preferably from 0.25 to 0.50, yet even more preferably from 0.30 to 0.40. In step b) of the method as defined herein, the self-healing polymer can be obtained by reacting the furan-functionalized prepolymer and the at least one polymaleimide at any temperature of at least 30 °C. It is however preferred to react the mixture at a higher temperature than 30 °C to enhance the reaction kinetics. It is also preferred to react the mixture at a first reaction of at most 200 °C to avoid side-reactions. In a preferred embodiment, the present invention provides the method as defined herein, wherein the second reaction temperature is from 30 to 200 °C, preferably from 40 to 180 °C, more preferably from 50 to 160 °C, even more preferably from 60 to 140 °C, yet even more preferably from 70 to 130 °C.

[0163] It further appeared that the presence of a radical scavenger during the reaction of the furan-functionalized prepolymer and the at least one polymaleimide in step b), may lead to improved properties of the self-healing polymer, for instance by at least partly suppressing the irreversible homopolymerization of the maleimide groups. In useful embodiments, the present invention provides the method as defined herein, wherein in step b) a radical scavenger is present during the reaction of the furan-functionalized prepolymer and the at least one polymaleimide. Any radical scavenger known in the art capable of suppressing monomer homopolymerization may be suitably used. Suitable examples are hydroquinone, butylated hydroxytoluene, 4-tert-butylcatechol, methyl-p-benzoquinone, and the like.

[0164] In a specific embodiment, the present invention provides the method as defined herein, comprising the steps of:

[0165] a1) reacting the mixture comprising the at least one mono-epoxy compound, the at least one bis-epoxy compound, the furfuryl amine, and optionally the one or more further amines, at the first reaction temperature of at least 30 °C, thereby obtaining the reaction mixture comprising the furan-functionalized prepolymer;

[0166] a2) adding the at least one polymaleimide and one or more radical scavengers to the reaction mixture comprising the furan-functionalized prepolymer obtained in step a1); and

[0167] b) reacting the furan-functionalized prepolymer obtained in step a1) with the at least one polymaleimide, in the presence of the radical scavenger, at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer.

[0168] It was further found that crosslinking the furan-functionalized prepolymer obtained in step a), before reacting it with the at least one polymaleimide in step b), of the method as defined herein, may provide a self-healing polymer with improved mechanical properties. Crosslinking of the furan-functionalized prepolymer can be achieved in different ways. When the furan-functionalized prepolymer is already crosslinked before it is reacted with the at least one polymaleimide, it may also be referred to as “partially crosslinked furan-functionalized prepolymer”.

[0169] Crosslinking of the furan-functionalized prepolymer can be achieved by the presence of a polyepoxy compound having three or more epoxy functionalities in the mixture in step a) of the method as defined herein. In particular embodiments, the present invention provides the method as defined herein, wherein in step a), the mixture further comprises at least one tris-epoxy compound, and the mixture is reacted at a first reaction temperature of at least 30 °C, thereby obtaining a partially crosslinked furan-functionalized prepolymer; and wherein in step b), the partially crosslinked furan-functionalized prepolymer is reacted with the at least one polymaleimide at a second reaction temperature of at least 30 °C, to obtain the self-healing polymer.

[0170] In the context of the present invention, the term ‘(a) tris-epoxy compound(s)’ refers to (a) chemically defined compound(s) having three epoxide or oxirane moieties, in particular three glycidyl ether moieties, and may be represented by formula (F)

[0171]

[0172] wherein

[0173] Y is selected from any substituted or unsubstituted alkylene, any substituted or unsubstituted alkenylene, any substituted or unsubstituted alkynylene, any substituted or unsubstituted aryl, any oligomer, or any polymer.

[0174] In embodiments, the present invention provides the method as defined herein, wherein the at least one tris-epoxy compound, and optionally the one or more further tris-epoxy compounds, are represented by formula (V)

[0175]

[0176] wherein

[0177] Yi is selected from -Ci-i2alkylene-, -Cz-izalkenylene-, and aryl; wherein each of said -Ci- izalkylene-, -C2-i2alkenylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

[0178] In particular embodiments, the present invention provides the method as defined herein, wherein the at least one tris-epoxy compound, and optionally the one or more further tris-epoxy compounds, are selected from glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol triglycidyl ether, sorbitol triglycidyl ether, and triethanolamine triglycidyl ether.

[0179]

[0180] Scheme 4

[0181] Scheme 4 provides a schematic representation of the reaction taking place in step a) according to embodiments of the method as defined herein, wherein a mixture of at least one mono-epoxy compound (ME), at least one bis-epoxy compound (BE), at least one tris-epoxy compound (TE), and furfurylamine (FA) reacts to provide a partially crosslinked furan-functionalized prepolymer (pcFFP), wherein R, n, A and Y are as defined herein.

[0182] In a specific embodiment, the present invention provides the method as defined herein, comprising the steps of:

[0183] a1) reacting the mixture comprising the at least one mono-epoxy compound, the at least one bis-epoxy compound, at least one tris-epoxy compound, the furfuryl amine, and optionally the one or more further amines, at the first reaction temperature of at least 30 °C, thereby obtaining the partially crosslinked furan-functionalized prepolymer; a2) adding the at least one polymaleimide and one or more radical scavengers to the partially crosslinked furan-functionalized prepolymer obtained in step a1); and b) reacting the partially crosslinked furan-functionalized prepolymer obtained in step a2) with the at least one polymaleimide, in the presence of the radical scavenger, at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer.

[0184] Crosslinking of the furan-functionalized prepolymer can alternatively, or additionally, be achieved by the presence of a primary polyamine, such as a primary diamine or a primary triamine, in the mixture in step a) of the method as defined herein. In particular embodiments, the present invention provides the method as defined herein, wherein in step a), the mixture further comprises at least one primary polyamine, and the mixture is reacted at a first reaction temperature of at least 30 °C, thereby obtaining a partially crosslinked furan-functionalized prepolymer; and wherein in step b), the partially crosslinked furan-functionalized prepolymer obtained in step a) is reacted with the at least one polymaleimide at a second reaction temperature of at least 30 °C, to obtain the self-healing polymer.

[0185] Crosslinking of the furan-functionalized prepolymer can alternatively, or additionally, be achieved by reacting the furan-functionalized prepolymer, or the partially crosslinked furan functionalized prepolymer, obtained in step a), with a polyfunctional reagent, such as boric acid. When the furan-functionalized prepolymer is reacted with boric acid, the hydroxy functionalities react with the boric acid to form boric esters bonds, thereby providing the partially crosslinked furan-functionalized prepolymer. It was found that the boric esters bonds raise the de-gelation temperature of the self-healing polymer. Without willing to be bound by theory, it is believed that the boric esters bonds are able to exchange with each other at ambient temperature, while they still maintain structural strength of the self-healing polymer, even at elevated temperatures.

[0186] In particular embodiments, the present invention provides the method as defined herein, comprising the further step of reacting the furan-functionalized prepolymer obtained in step a) with boric acid, thereby obtaining a partially crosslinked furan-functionalized prepolymer; and wherein in step b), the partially crosslinked furan-functionalized prepolymer obtained the further step is reacted with the at least one polymaleimide at a second reaction temperature of at least 30 °C, to obtain the self-healing polymer.

[0187] In a specific embodiment, the present invention provides the method as defined herein, comprising the steps of:

[0188] a1) reacting the mixture comprising the at least one mono-epoxy compound, the at least one bis-epoxy compound, the furfuryl amine, and optionally the one or more further amines, at the first reaction temperature of at least 30 °C, thereby obtaining the reaction mixture comprising the furan-functionalized prepolymer;

[0189] a2) reacting the furan-functionalized prepolymer obtained in step a) with boric acid, thereby obtaining a partially crosslinked furan-functionalized prepolymer;

[0190] a3) adding the at least one polymaleimide and one or more radical scavengers to the partially crosslinked furan-functionalized prepolymer obtained in step a2); and b) reacting the partially crosslinked furan-functionalized prepolymer obtained in step a3) with the at least one polymaleimide, in the presence of the radical scavenger, at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer.

[0191] Scheme 5 provides a schematic representation of the reaction taking place in step a2) according to embodiments of the method as defined herein, wherein a furan-functionalized prepolymer (FFP) reacts with boric acid (B(OH)3) to provide a partially crosslinked furan-functionalized prepolymer (pcFFP), wherein R, n and A and are as defined herein.

[0192] In embodiment of the present invention, the molar ratio of boric acid, relative to hydroxy (OH) functionality of the furan-functionalized prepolymer, is from 0.02 to 0.16, preferably from 0.03 to 0.12, more preferably from 0.04 to 0.10.

[0193]

[0194] pcFFP

[0195] Scheme 5

[0196] As stated hereinbefore, according to a second aspect, the present invention provides a self-healing polymer obtainable by the method as defined herein.

[0197] The self-healing polymer as defined herein has the advantage that it can be readily prepared by the method as defined herein. A further advantage of the self-healing polymer as defined herein, is that it is particularly suitable to be used for puncture-proofing tires, in particular for bicycle tires and car tires. Indeed, the self-healing polymer as defined herein may have self-healing properties at ambient or sub-ambient temperatures, which is important for self-healing tires, such as car tires or bicycle tires. The self-healing polymer as defined herein in particular may provide a combination of self-healing, softness, tackiness, and high elasticity, which is an uncommon combination in materials science.

[0198] In an embodiment, the present invention provides the self-healing polymer as defined herein, wherein the self-healing polymer comprises the Diels-Alder reaction product of a furan-functionalized prepolymer and at least one polymaleimide; wherein the furan-functionalized prepolymer is represented by formula (III)

[0199]

[0200] wherein

[0201] n is an integer from 2 to 100;

[0202] m is 1 , or an integer from 2 to 100;

[0203] Ai is selected from -Ci-i2alkylene-, and -C2-i2alkenylene-; and

[0204] Ri is selected from -Ci-isalkyl, -C2-i8alkenyl, -C2-i8alkynyl, and aryl; wherein each of said - Ci-isalkyl, -C2-i8alkenyl, -C2-i8alkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents; and

[0205] wherein the at least one polymaleimide , and optionally the one or more further polymaleimides, are bismaleimides represented by formula (IV)

[0206]

[0207] wherein

[0208] Xi is selected from -Ci-isalkylene-, -C2-i8alkenylene-, -C2-i8alkynylene-, aryl, and any combination of two thereof; wherein each of said -Ci-isalkylene-, -C2-i8alkenylene-, -C2- isalkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

[0209] In useful embodiments, the present invention provides the self-healing polymer as defined herein, wherein one or more of the following applies: n is an integer from 2 to 100;

[0210] in particular, n is an integer from 2 to 50;

[0211] more in particular, n is an integer from 3 to 25;

[0212] even more in particular, n is an integer from 4 to 15;

[0213] yet even more in particular, n is an integer from 5 to 10;

[0214] m is 1 , or m is an integer from 2 to 50;

[0215] in particular, m is an integer from 3 to 40;

[0216] more in particular, m is an integer from 4 to 30;

[0217] even more in particular, m is an integer from 5 to 20;

[0218] yet even more in particular, m is an integer from 6 to 15;

[0219] yet even more in particular, m is an integer from 7 to 12;

[0220] Ai is selected from -Ci-walkylene-, and -C2-walkenylene-,;

[0221] in particular, Ai is -Ci-i2alkylene-;

[0222] more in particular, Ai is -Ci- alkylene-;

[0223] even more in particular, Ai is -C2-salkylene-;

[0224] yet even more in particular, Ai is -C2-ealkylene-;

[0225] yet even more in particular, Ai is -C2-4alkylene-;

[0226] Ri is selected from -Ci alkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl; wherein each of said -Ci- alkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents;

[0227] in particular, Ri is selected from -Ci alkyl, and aryl;

[0228] Xi is selected from -Ci- alkylene-, -C2-walkenylene-, -C2-walkynylene-, aryl, and any combination of two thereof; wherein each of said -Ci- alkylene-, -C2-walkenylene-, -C2-walkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents; and

[0229] in particular, Xi is selected from -Ci-walkylene, aryl, and any combination thereof; wherein each of said -Ci-walkylene-, and aryl optionally comprises one or more substituents selected from -halo, -Ciwalkyl, and -O-Ciwalkyl.

[0230] In embodiments, the present invention provides the self-healing polymer as defined herein, wherein the molar ratio of maleimide functionality of the at least one polymaleimide, relative to furan functionality of the furan-functionalized prepolymer, is from 0.05 to 0.95, preferably from 0.15 to 0.90, more preferably from 0.25 to 0.80, even more preferably from 0.30 to 0.70, yet even more preferably from 0.35 to 0.60. In embodiments, the present invention provides the self-healing polymer as defined herein, wherein the average molecular weight of the furan-functionalized prepolymer, based on the stoichiometry of the reagents used, is from 2500 to 10 000 g / mol, preferably from 3500 to 6000 g / mol. In particular embodiments, the present invention provides the self-healing polymer as defined herein, wherein the weight average molecular weight Mw of the furan-functionalized prepolymer, as determined by GPC, is from 2500 to 10000 g / mol, preferably from 3500 to 9000 g / mol, more preferably from 4500 to 8000 g / mol, even more preferably from 5000 to 7500 g / mol.

[0231] In a particular embodiment, the present invention provides the self-healing polymer as defined herein, wherein the furan-functionalized prepolymer is a partially crosslinked furan-functionalized prepolymer obtained by reacting the furan-functionalized prepolymer with boric acid.

[0232] According to a further aspect, the present invention provides a composition comprising the self-healing polymer as defined herein. The composition may further comprise additives, said additives adding functionality or characteristics such as color, texture, tactile experience, flexibility, processability, viscosity at higher temperatures, electrical or magnetic properties and the like to the self-healing polymer composition.

[0233] According to a further aspect, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein.

[0234] It appeared that the self-healing polymer as defined herein is particularly suitable to be used as self-healing material. It further appeared that the self-healing polymer as defined herein is particularly suitable to be used in the field of robotics, more specifically in the subfield of soft robotics. It was also found that the self-healing polymer as defined herein provides shapememory properties, and therefore may be used as a shape-memory material.

[0235] It was further found that the self-healing polymer as defined herein is suitable to be used in pneumatic vehicle tires, in particular as a sealant material for bicycle tires or car tires, thereby providing so-called self-sealing tires. The self-healing polymer as defined herein has several advantages, compared to sealants for self-sealing tires known in the art, such as butylrubber based sealants. The self-healing polymer as defined herein has the advantage that it can be easily and evenly applied on the inside of a pneumatic vehicle tire, for instance by extrusion, casting, spraying, screen printing, or injection moulding. The self-healing polymer as defined herein has the further advantage that it is capable of sealing a hole in the tire when the foreign object is still present, by self-healing around the foreign object. The biggest advantage, however, of the self-healing polymer as defined herein, is that it is also capable of sealing the hole in the tire when the foreign object is removed, due to its self-healing properties. When the foreign object is removed, furan and maleimide functional groups of the self-healing polymer in the vicinity of the hole interact with each other and autonomously create new Diels-Alder bonds, thereby closing the hole. Another advantage of the self-healing polymer as defined herein is that the presence of the self-healing polymer in an end-of-life tire does not hamper the recyclability of the car.

[0236] As used herein and unless provided otherwise, the term “soft robotics” should be understood as a subfield of robotics covering the construction of robotic parts and robots from different types of materials approaching the properties of those found in living organisms. These materials often require a certain amount of flexibility and adaptability depending on their specific purpose.

[0237] Shape-memory is a known term in the art and refers to the ability of certain materials to ‘remember’ and return to their original shape after being deformed. This property is often induced through a phase transition in the material, such as a change in temperature or stress. When subjected to a specific stimulus, such as heating or cooling, these materials can undergo reversible deformation, making them valuable in situations where precise shape changes are required.

[0238] In an embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, as self-healing material. In a further embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, as shape-memory material. In a further embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, in pneumatic tires for vehicles. In a particular embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, as a sealant in pneumatic tires for vehicles, in particular in bicycle tires or car tires.

[0239] In another embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, in the manufacturing of 1 D, 2D or 3D structures. In a particular embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, in the manufacturing of robotic components, seals, gaskets, or tires.

[0240] In another embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, in a manufacturing method selected from filament extrusion, extrusion-based printing techniques, selective laser sintering, injection molding, compression molding, casting, and soft lithography. In a particular embodiment, the present invention provides the use of the self-healing polymer, in particular the composition, as defined herein, in extrusion-based printing techniques selected from fused filament fabrication, direct ink writing, and the like.

[0241] According to a further aspect, the present invention provides a 1 D, 2D or 3D structure comprising the self-healing polymer, in particular the composition, as defined herein.

[0242] In a particular embodiment, the present invention provides the 1 D, 2D or 3D structure as defined herein, wherein the structure is selected from robotic components, seals, gaskets, or tires. In a specific embodiment, the present invention provides a tire comprising the self-healing polymer, in particular the composition, as defined herein. In a more specific embodiment, the present invention provides a pneumatic vehicle tire comprising the self-healing polymer, in particular the composition, as defined herein, in particular a bicycle tire or car tire. In an even more specific embodiment, the present invention provides a pneumatic vehicle tire, wherein the self-healing polymer, in particular the composition, as defined herein, is applied on the inside of the tire to protect the tire from punctures of foreign objects, such as nails, screws, shards of glass, and the like.

[0243] The compounds of the present invention can be prepared according to the method(s) provided in the examples hereinafter, but those skilled in the art will appreciate that these are only illustrative for the invention and that the compounds of this invention can be prepared by any of several standard synthetic processes commonly used by those skilled in the art of organic chemistry.

[0244] EXAMPLES

[0245] Materials

[0246] Poly(tetramethyleneoxide) diglycidyl ether (RD-21), C12-C14 alcohol glycidyl ether (RD-24), neopentylglycol diglycidyl ether (RD-14) and trimethylolpropane triglycidyl ether (RD-20) were purchased from Ipox-Chemicals (Germany). Furfurylamine (FA), tert-butyl catechol (TBC), boric acid (BA), poly(dimethylsiloxane) diglycidyl ether (SEpoxy) (Mw = 840), and diphenyl bismaleimide (DPBM) were purchased from Sigma Aldrich (Germany). All products were used as received unless stated otherwise.

[0247] Analysis

[0248] Proton nuclear magnetic resonance (1H NMR) spectroscopy was conducted on a Bruker Avance DRX 250 spectrometer operating at a frequency of 250 MHz. The analysis was carried out at room temperature using deuterated chloroform (CDCh) as the solvent and tetramethylsilane (TMS) as the internal standard. The samples analyzed had a concentration of 10 mg / mL.

[0249] Fourier transform infrared (FTIR) spectroscopy was performed using a Nicolet 6700 FTIR spectrometer from Thermo Scientific at ambient temperature. The spectra were acquired using the OMNIC software package, with each spectrum averaged from 32 scans recorded in the range of 4000 cm-1to 600 cm-1.

[0250] Differential scanning calorimetry (DSC) measurements were conducted using a TA Instruments Discovery DSC, equipped with a refrigerated cooling system (RCS). The experiments were carried out in Tzero-hermetic aluminum pans, with nitrogen used as the purge gas. The heating and cooling rates were set to 5 °C / min.

[0251] Dynamic rheometry was carried out using a TA Instruments Discovery Hybrid Rheometer (DHR2). The samples were prepared by cutting them into circular shapes and placing them between 8 mm diameter aluminum parallel plates. Three tests were performed on the materials. The samples were subjected to an oscillatory strain of 1% across various frequencies: 0.312, 0.562, 1 .0, 1 .778, and 3.125 Hz. Simultaneously, a temperature ramp from 40 °C to 120 °C was applied to determine the gelation transition temperature (gel point).

[0252] Tensile test analysis measuring Young's modulus and Tensile strength: Tensile testing was performed on a TA Instruments DMA Q800 at ambient temperature. Stress-strain tests were performed at room temperature using a film tension clamp. Rectangular specimens with a thickness of 2mm and width of 3 mm were clamped with and strained at a rate of 60% min-1. At least three tensile specimens were tested, and the results were averaged.

[0253] GPC measurement were carried out using an Agilent GPC / SEC with a Rl-detector, THF flow of 1 ml / min columns at 35°C. A polystyrene standard was used. The following columns were used (as supplied by PSS Germany): 1 x SDV precolumn 3pm 8x50mm (P / N sda080503), SDV column 3pm 1000A 8x300mm (P / N sda0830031e3), SDV column 3pm 10e4A 8x300mm (P / N sda0830031e4). Samples for GPC measurements were prepared by dissolving 50 mg of prepolymer in 10 mL of THF. For each measurement, 50 pL of the as-prepared solutions were injected into the GPC instrument.

[0254] To determine the self-healing efficiency, three specimens with a thickness of 2 mm and width of 3 mm were cut in half by using a blade and put together for 2 hours at ambient temperature for self-healing. The same tensile test analysis as described above was performed on each sample and the self-healing efficiency (%) was calculated as the ratio of the maximum strain after self-healing (Smax h) and the initial maximum strain before the cut (Smaxi), according to the following equation:

[0255] Self-healing efficiency (%) = ^4 x 100

[0256] max i Synthesis

[0257] Example 1. Preparation of a furan-functionalized prepolymer

[0258] Nucleophilic chain extension reaction of epoxy resins was carried out by reacting poly(tetramethyleneoxide) diglycidyl ether (Mw = 840) as a bisepoxy resin with furfurylamine in presence of C12-C14 alcohol glycidyl ether as a mono-epoxy resin. To prepare the prepolymer, a glass reactor was fed with 20.73 g of poly(tetramethyleneoxide) diglycidyl ether, 3.94 g C12-C14 alcohol glycidyl ether, and 3.07 g of furfurylamine. The mixture was magnetically stirred at 90 °C for 1 h and then at 120 °C for 2h to provide the prepolymer. The average molecular weight of the prepolymer was calculated to be 4000 g / mol, based on the stoichiometry of the reagents used. The weight average molecular weight Mw of the prepolymer, as determined by GPC, was 5416 g / mol.

[0259] Example 2. Preparation of a furan-functionalized prepolymer

[0260] A prepolymer was prepared according to the procedure described in Example 1 , but by using 22.36 g of poly(tetramethyleneoxide) diglycidyl ether, 2.43 g C12-C14 alcohol glycidyl ether, and 3.00 g of furfurylamine. The average molecular weight of the obtained prepolymer was calculated to be 6500 g / mol. The weight average molecular weight Mw of the prepolymer, as determined by GPC, was 6389 g / mol.

[0261] Example 3. Preparation of a furan-functionalized prepolymer

[0262] A prepolymer was prepared according to the procedure described in Example 1 , but by using 22.85 g of poly(tetramethyleneoxide) diglycidyl ether, 1 .97 g C12-C14 alcohol glycidyl ether, and 2.98 g of furfurylamine. The average molecular weight of the obtained prepolymer was calculated to be 8000 g / mol. The weight average molecular weight Mw of the prepolymer, as determined by GPC, was 7195 g / mol.

[0263] Example 4. Preparation of a partially crosslinked furan-functionalized prepolymer A partially crosslinked prepolymer was prepared according to the procedure described in Example 1 , but by using 1.5 g of trimethylolpropane triglycidyl ether, 19.23 g of poly(tetramethyleneoxide) diglycidyl ether, 3.93 g of C12-C14 alcohol glycidyl ether, and 3.39 g of furfurylamine.

[0264] Example 5. Preparation of a partially crosslinked furan-functionalized prepolymer Prepolymers were prepared according to the procedure described in Example 1 , but instead of isolating the prepolymers after heating to 120 °C, the temperature of the mixture was increased to 150 °C and different ratios of boric acid were added to the mixture according to Table 1 . The mixture was subsequently stirred at 150 °C for 1 h to provide partially crosslinked prepolymers. Table 1. Composition data of Examples 5a-5d

[0265]

[0266] Example 6. Preparation of a furan containing prepolymer with two bisepoxy resins Prepolymers were prepared according to the procedure described in Example 1 , but by using two different bis-epoxy compounds in different ratios according to Table 2.

[0267] Table 2. Composition data of Examples 6a-6d

[0268]

[0269] Example 7. Preparation of a silicone modified furan-functionalized prepolymer

[0270] A silicone modified prepolymer was prepared according to the procedure described in Example 1 , but by using two different bis-epoxy compounds in different ratios according to Table 3. The reaction mixtures were stirred at 90 °C for 1 h and then at 130 °C for 4h to provide the silicone modified prepolymer.

[0271] Table 3. Composition data of Examples 7a-7d

[0272]

[0273] Example 8. Preparation of self-healing polymers

[0274] Self-healing polymers were prepared by reacting the furan-functionalized prepolymers according to Examples 1-7 with a bismaleimide compound in different ratios according to Table 4. For this purpose, a prepolymer was heated up to 150 °C and then 1 wt.% of tert-butyl catechol was added to the mixture as an inhibitor. Subsequently diphenyl bismaleimide was added to the mixture, and mixing at 150 °C was continued until the diphenyl bismaleimide was fully melted, thereby forming a transparent solution. The resulting mixture was poured into a mould and allowed to cool down to provide the self-healing polymers.

[0275] Table 4. Composition data of Examples 8a-8r

[0276]

[0277] Table 5 provides an overview of the Young's modulus, tensile strength, gel point and self-healing efficiency of selected examples self-healing polymers prepared according to Example 8.

[0278] Table 5. Analysis data of Examples 8a-8c, 8i-8l

[0279]

[0280]

[0281] n.d. is not determined

[0282] Selected self-healing polymers prepared according to Example 8 were further evaluated for their efficacy in endowing puncture resistance properties in both bike tires and car tires. For this purpose, a patch of approximately 4 by 10 cm, with a thickness of 2 mm, of the self-healing polymers was applied on Pro One tubeless tires, ADDIX race by heating the self-heating polymers above 80 °C and manually casting the self-healing polymers on the inside of the tires. After casting, the patches were cooled down to room temperature, followed by 3 days of stabilization.

[0283] The tires were subsequently subjected to dynamic puncture tests, by subsequently 1) pressurizing a tire to approximately 6 bars, 1 ) puncturing the tire with three nails with a thickness of 3 mm, 2) pulling out the nails, 3) rolling the tire for 30 min under 20 kg load on a tire rolling machine, and 4) tracking the tire pressure with a wireless digital barometer sensor.

[0284] Figures 1 A-1 J provide a representation of the pressure evolution of tires coated with self-healing polymers prepared according to examples 8a, 8b 8c, 8i, 8j, 8k, 8I, 8m, 8o and 8p, respectively, and subjected to the dynamic puncture tests as described above. It was found that the tested tires showed a pressure drop of less than 25%, in particular less than 10%, more in particular less than 5%.

[0285] Comparative example A

[0286] An aromatic furan-functionalized prepolymer was prepared similar to example 1 , by combining 64.87 g of Bisphenol A diglycidyl ether (BADGE), 14.20 g of RD24 mono-epoxy, and 20.93 g of furfurylamine in a glass container equipped with a magnetic stirrer. The mixture was stirred at 90 °C for 1 hour, followed by an additional 2 hours at 150 °C. The resulting prepolymer exhibited a molecular weight of approximately 4000 g / mol, based on the stoichiometry of the reagents used.

[0287] Diels-Alder polymers were prepared by reacting the aromatic furan-functionalized prepolymer with a bismaleimide compound in different ratios according to Table 6, similar to example 8. Instead of 150 °C, the aromatic furan-functionalized prepolymer was heated to 160 °C, before adding tert-butyl catechol as a polymerization inhibitor, and diphenyl bismaleimide. Table 6. Composition data of Comparative examples A1-A3

[0288]

[0289] Table 7 provides an overview of the Young's modulus, tensile strength, gel point and self-healing efficiency of the Diels-Alder polymers prepared according to Comparative example A.

[0290] Table 7. Analysis data of Comparative examples A1-A3

[0291]

[0292] As can be seen from Table 7, the Diels-Alder polymers prepared with an aromatic furan-functionalized prepolymer are not capable of self-healing at ambient temperature. It was moreover found that the Diels-Alder polymers prepared with an aromatic furan-functionalized prepolymer were too rigid and stiff to adhere to (the inside of) a tire. Diels-Alder polymers prepared with an aromatic furan-functionalized prepolymer are therefore unsuitable for manufacturing self-healing bicycle and car tires.

Claims

CLAIMS1 . A method for preparing a self-healing polymer, the method comprising the steps of:a) reacting a mixture comprising at least one mono-epoxy compound, at least one bisepoxy compound, furfuryl amine, and optionally one or more further amines, at a first reaction temperature of at least 30 °C, thereby obtaining a reaction mixture comprising a furan-functionalized prepolymer; andb) reacting the furan-functionalized prepolymer obtained in step a) with at least one polymaleimide at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer;wherein the at least one mono-epoxy compound is represented by formula (I)whereinRi is selected from -Ci alkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl; wherein each of said - Ci-isalkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents; andwherein the at least one bis-epoxy compound is represented by formula (II)whereinm is 1 , or an integer from 2 to 100; andAi is selected from -Ci-i2alkylene-, and -C2-i2alkenylene-.

2. The method as claimed in claim 1 , wherein the molar ratio of epoxy functionality of the total amount of the bis-epoxy compounds, relative to the total amount of the mono-epoxy compounds, is from 1 to 6.5, preferably from 1 .5 to 3.5, more preferably from 1 .7 to 2.9.

3. The method as claimed in claim 1 or 2, wherein the at least one mono-epoxy compound is independently selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether.

4. The method as claimed in claim 1 or 2, wherein the at least one mono-epoxy compound is C12-C14 alcohol glycidyl ether.

5. The method as claimed in any one of claims 1 to 4, wherein the at least one bis-epoxy compound is selected from 1 ,3-propanediol diglycidyl ether, 1 ,4-butanediol diglycidyl ether,1 ,5-pentanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1 ,6-hexanediol diglycidyl ether, 1 ,10-decanediol diglycidyl ether, polyethyleneglycol diglycidyl ether, polypropyleneglycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether.

6. The method as claimed in any one of claims 1 to 5, wherein the at least one polymaleimide is a bismaleimide represented by formula (IV)whereinXi is selected from -Ci alkylene-, -Cz- alkenylene-, -Cz- alkynylene-, aryl, and any combination of two or more thereof; wherein each of said -Ci walkylene-, -C2-isalkenylene-, -Cz-isalkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

7. The method as claimed in any one of claims 1 to 6, wherein the at least one polymaleimide is a bismaleimide selected from 1,1’-(methylenedi-4,1-phenylene)bismaleimide, N,N’-(1,3- phenylene)bismaleimide, N,N’-(4-methyl-1 ,3-phenylene)-bismaleimide, 4,4'- bis(maleimidophenyl) ether, N,N'-Bismaleimido-1 ,2-ethane, N,N'-Bismaleimido-1 ,3- propane, N,N'-Bismaleimido-1 ,4-butane, N,N'-Bismaleimido-1 ,5-pentane, N,N'- Bismaleimido-1 ,6-hexane, N,N'-Bismaleimido-1 ,9-nonane, N,N'-Bismaleimido-1 ,10- decane, N,N'-Bismaleimido-1 ,12-dodecane, and N,N'-Bismaleimido-2-methyl-1 ,3-propane.

8. The method as claimed in any one of claims 1 to 7, wherein the molar ratio of maleimide functionality of the at least one polymaleimide, relative to furan functionality of the furan- functionalized prepolymer, reacted in step b), is from 0.05 to 0.95, preferably from 0.10 to 0.80, more preferably from 0.15 to 0.65, even more preferably from 0.20 to 0.55, yet even more preferably from 0.25 to 0.50, yet even more preferably from 0.30 to 0.40.

9. The method as claimed in any one of claims 1 to 8, comprising the further step of reacting the furan-functionalized prepolymer obtained in step a) with boric acid, thereby obtaining a partially crosslinked furan-functionalized prepolymer; and wherein in step b), the partially crosslinked furan-functionalized prepolymer is reacted with the at least one polymaleimide at a second reaction temperature of at least 30 °C, thereby obtaining the self-healing polymer.

10. A self-healing polymer obtainable by the method as claimed in any one of claims 1 to 9.11 . Self-healing polymer comprising the Diels-Alder reaction product of a furan-functionalized prepolymer and at least one polymaleimide;wherein the furan-functionalized prepolymer is represented by formula (III)whereinn is an integer from 2 to 100;m is 1 , or an integer from 2 to 100;Ai is selected from -Ci-i2alkylene-, and -C2-i2alkenylene-; andRi is selected from -Ci alkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl; wherein each of said -Ci walkyl, -C2-isalkenyl, -C2-isalkynyl, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents; andwherein the at least one polymaleimide is a bismaleimide represented by formula (IV)whereinXi is selected from -Ci alkylene-, -C2-isalkenylene-, -C2-isalkynylene-, aryl, and any combination of two or more thereof; wherein each of said -Ci alkylene-, -C2- alkenylene-, -C2-isalkynylene-, and aryl optionally comprises one or more heteroatoms selected from O, N and S and / or is optionally and independently substituted with one or more substituents.

12. Self-healing polymer as claimed in claim 10 or 11 , wherein the weight average molecular weight Mw of the furan-functionalized prepolymer, as determined by GPC, is from 2500 to 10000 g / mol, preferably from 3500 to 9000 g / mol, more preferably from 4500 to 8000 g / mol, even more preferably from 5000 to 7500 g / mol.

13. Self-healing polymer as claimed in claim 10 or 11 , wherein the furan-functionalized prepolymer is a partially crosslinked furan-functionalized prepolymer obtained by reactingthe furan-functionalized prepolymer with boric acid.

14. Use of the self-healing polymer as claimed in any one of claims 10 to 13 in the manufacturing of 1 D, 2D or 3D structures, in particular in the manufacturing of pneumatic tires.

15. A 1 D, 2D or 3D structure, in particular a pneumatic tire, comprising the self-healing polymer as claimed in any one of claims 10 to 13.

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