Synthesis of self-healing benzoxazine polymers by melt polymerization

Abstract

Self-healing resin compositions are provided, which are polymers formed from the reaction of a thermoplastic polymer having terminal functional groups with a benzoxazine compound. Methods for forming such self-healing resin compositions are also provided. Methods for self-healing an article are also provided. In such methods, the article may have a break and may be formed from a polymer resulting from the reaction between a thermoplastic polymer having terminal functional groups and a benzoxazine compound. The method may include maintaining the article formed from the polymer at a predetermined temperature for a predetermined time, such that the break is healed.

Description

Detailed Description of the Invention

[0001] 〔background〕 Self-healing polymers are commercially valuable materials because products constructed from such materials can exhibit higher durability, longer life spans, and the ability to repair and / or recover from damage. Repair processes are generally classified as exogenous (i.e., an external agent helps repair the damaged matrix) or endogenous (i.e., repair is driven by molecular properties of the matrix itself) and can exhibit either non-autonomous (i.e., requiring an external trigger (e.g., heat, etc.) to initiate repair) or autonomous (i.e., self-repair occurs without an external trigger) modes.

[0002] Several repair approaches are known in the literature, such as dispersions of microcapsules with reactive monomers in polymers, dispersions of flowable thermoplastics in thermosetting resins, matrices capable of undergoing reversible chemical reactions, and polymers exhibiting supramolecular interactions. Applications can span a variety of fields, including scratch-recoverable surface coatings and crack repair in composites, electronic, aerospace, and automotive components.

[0003] 〔summary〕 This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In one aspect, embodiments disclosed herein relate to a self-healing resin composition having a polymer formed from the reaction of a thermoplastic polymer having a terminal functional group with a benzoxazine compound, wherein the terminal functional group is selected from the group consisting of a primary amine, a secondary amine, a thiol, a phenolic compound, and combinations thereof.

[0005] In another aspect, embodiments disclosed herein relate to a method of forming a self-healing resin composition, comprising reacting by melt polymerization a benzoxazine compound with a thermoplastic polymer having a terminal functional group, wherein the terminal functional group is selected from the group consisting of a primary amine, a secondary amine, a thiol, a phenolic compound, and combinations thereof.

[0006] In yet another aspect, embodiments disclosed herein relate to a method of self-healing an article formed from a polymer resulting from a reaction between a thermoplastic polymer having a terminal functional group and a benzoxazine compound, the terminal functional group being selected from the group consisting of a primary amine, a secondary amine, a thiol, a phenolic compound, and combinations thereof, the article having a break, the method comprising maintaining the article formed from the polymer at a predetermined temperature for a predetermined time such that the break is healed.

[0007] Other aspects and advantages of the claimed subject matter will become apparent from the following description and the appended claims.

[0008] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an exemplary self-healing resin according to one or more embodiments of the present disclosure.

[0009] FIG. 1B is an exemplary self-healing resin according to one or more embodiments of the present disclosure.

[0010] FIG. 1C is an exemplary self-healing resin according to one or more embodiments of the present disclosure.

[0011] FIG. 2A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure.

[0012] FIG. 2B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0013] FIG. 3A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure.

[0014] FIG. 3B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0015] FIG. 4A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure.

[0016] FIG. 4B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0017] FIG. 5A is a photograph of a polymer having a cleavage according to one or more embodiments of the present disclosure.

[0018] FIG. 5B is a photograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0019] FIG. 6A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure.

[0020] FIG. 6B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0021] FIG. 6C is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0022] FIG. 7A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure.

[0023] FIG. 7B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0024] FIG. 7C is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

[0025] Detailed Description The present disclosure generally relates to polymers with self-healing properties. The self-healing properties may be at least partially due to dynamic molecular mobility in the polymer, supramolecular interactions (e.g., hydrogen bonding, etc.), and metal-ligand interactions. Such polymers may have self-healing properties at room temperature and high temperature conditions.

[0026] In one or more embodiments, the self-healing resin composition of the present disclosure may include a polymer formed from the reaction between a thermoplastic polymer having terminal functional groups and a benzoxazine (BZ) compound.

[0027] The thermoplastic polymer having a terminal functional group according to one or more embodiments of the present disclosure is not particularly limited. In some embodiments, the thermoplastic polymer can be any suitable thermoplastic polymer, so long as it has a terminal functional group for reacting with a BZ compound. The terminal functional group can include a primary amine, a secondary amine, a thiol, and / or a phenolic compound. As used herein, "phenolic compound" includes phenol and substituted phenol, which is a phenol containing additional functional groups (e.g., a hydrocarbon group, a substituted hydrocarbon group, a hydroxyl group, or a functional group, etc.). The thermoplastic polymer can include a polymer backbone having amine, siloxane, ether, alkyl, and / or phenolic functional groups. In some embodiments, the thermoplastic polymer can be a polyether polymer, a polysiloxane polymer, or a polyalkyl polymer.

[0028] In some embodiments, the thermoplastic polymer can be a polyether having a structure represented by formula (I):

[0029] [ka]

[0030] wherein y is approximately 1 to 40, and x+z is approximately 1 to 8. In some embodiments, y may have a lower limit of 1, 2, 5, or 9, and an upper limit of 13, 20, 36, 39, or 40, any lower limit may be paired with any mathematically compatible upper limit. In some embodiments, x+z may have a lower limit of 1, 1.2, or 2, and an upper limit of 4, 6, or 8, any lower limit may be paired with any mathematically compatible upper limit. Each of R1 and R1' may represent a functional group independently selected from primary amines, secondary amines, thiols, and phenolic compounds.

[0031] In some embodiments, the thermoplastic polymer can be a polyether having a structure represented by formula (II):

[0032] [ka]

[0033] where x is approximately 2 to 70. In some embodiments, x can have a lower limit of any of 2, 2.5, or 5, and an upper limit of any of 20, 35, and 70, any lower limit paired with any mathematically compatible upper limit. In some embodiments, x can be about 2.5, 6.1, or 68. Each of R2 and R2' can represent a functional group independently selected from a primary amine, a secondary amine, a thiol, or a phenolic compound.

[0034] The thermoplastic polymer having end groups according to one or more embodiments of the present disclosure may have a weight average molecular weight (Mw) ranging from approximately 500 to 4,000 Da (Daltons). For example, the thermoplastic polymer may have a molecular weight of approximately 500 to 4,000 Da. In some embodiments, the molecular weight may have a lower limit of any one of 500, 750, 1,000, 1,500, and 2,000, and an upper limit of any one of 2,500, 2,750, 3,000, 3,500, and 4,000, and any lower limit may be paired with any mathematically compatible upper limit.

[0035] In one or more embodiments, one or more thermoplastic polymers may be used to form the self-healing resin. A combination of thermoplastic polymers may be included in the composition. In one or more embodiments, a combination of thermoplastic polymers having different types of terminal functional groups may be included.

[0036] In one or more embodiments, the BZ compounds can be reacted with the thermoplastic polymers described above to form self-healing resins. The BZ compounds generally contain one or two benzoxazine (BZ) moieties. The first benzoxazine moiety is represented by the structure of formula (III):

[0037] [ka]

[0038] wherein each of R3 and R4 may represent one or more of a hydrogen atom, a hydrocarbon group, a substituted hydrocarbon group, a functional group, or a second BZ moiety. However, in some embodiments, one of R3 and R4 is a second BZ moiety, i.e., a di-BZ compound. As used herein, the term "hydrocarbon group" may refer to a branched, linear, and / or ring-containing hydrocarbon group that may be saturated or unsaturated. The hydrocarbon group may be a primary, secondary, and / or tertiary hydrocarbon. As used herein, the term "substituted hydrocarbon group" may refer to a hydrocarbon group (as defined above) in which at least one hydrogen atom has been replaced with a non-hydrogen group to provide a stable compound. Such substituents may be selected from, but are not limited to, halo, hydroxyl, alkoxy, oxo, alkanoyl, aryloxy, alkanoyloxy, amino, alkylamino, arylamino, arylalkylamino, disubstituted amine, alkanylamino, aroylamino, aralkanoylamino, substituted alkanoylamino, substituted arylamino, substituted aralkanoylamino, thiol, alkylthio, arylthio, arylalkylthio, alkylthiono, arylthiono, arylalkylthiono, alkylsulfonyl, arylsulfonyl, arylalkylsulfonyl, sulfonamido, substituted sulfonamido, nitro, cyano, carboxy, carbamyl, alkoxycarbonyl, aryl, substituted aryl, guanidine, and heterocyclyl, and mixtures thereof. The functional groups may be selected from, but are not limited to, halo, hydroxyl, alkoxy, oxo, amino, amido, thiol, alkylthio, sulfonyl, alkylsulfonyl, sulfonamido, substituted sulfonamido, nitro, cyano, carboxy, carbamyl, alkoxycarbonyl groups, and the like.

[0039] In one or more embodiments, the benzoxazine compound may be a di-benzoxazine compound (also referred to as a di-BZ compound), meaning that it has two BZ moieties. In one or more embodiments, the di-BZ compound may be a bis-di-BZ. In one or more embodiments, the bis-di-BZ compound unit may have a structure represented by formula (IV):

[0040] [ka]

[0041] wherein R5 represents a hydrogen atom, a hydrocarbon group, a substituted hydrocarbon group, or a functional group as described above with respect to formula (III). R5' may be the same group as R5 or a different group. R6 may represent a hydrocarbon group or a substituted hydrocarbon group. In certain embodiments, R6 may represent an aromatic group selected from, but not limited to, benzene, bibenzyl, diphenylmethane, naphthalene, anthracene, diphenyl ether, diphenyl sulfone ether, bis(phenoxy)benzene, stilbene, phenanthrene, fluorine, and substituted variants thereof.

[0042] In an exemplary embodiment, the di-benzoxazine compound can be a bisamine-type di-benzoxazine having a structure represented by formula (V):

[0043] [ka]

[0044] In some embodiments, the di-BZ compound can have a structure represented by formula (VI):

[0045] [ka]

[0046] In the formula, R7 represents a hydrogen atom, a hydrocarbon group, a substituted hydrocarbon group, or a functional group as described above with respect to formula (III). R7' may be the same group as R7 or a different group. R8 may be selected from, but is not limited to, hydrocarbon, ether, secondary amino, amide, thioether, sulfonyl, sulfonamide, carbonyl, carbamyl, fluorenyl, alkoxycarbonyl, and mixtures thereof.

[0047] In an exemplary embodiment, the di-BZ compound can be a bisphenol-type di-benzoxazine having a structure represented by formula (VII):

[0048] [ka]

[0049] In one or more embodiments, the BZ compound may include a ring-opened oligomer having a terminal benzoxazine moiety on one or both end caps. Such ring-opened oligomers are described in International Application No. PCT / IB2021 / 020018, which is incorporated by reference in its entirety. The ring-opened BZ oligomers may be reacted with the thermoplastic polymers described above to form self-healing resins, provided that at least one BZ functional group is present as an end cap.

[0050] In one or more embodiments, one or more benzoxazine compounds may be reacted with the thermoplastic polymers described above to form a self-healing resin.

[0051] In one or more embodiments, the resin composition may optionally be formulated with one or more functionalized compounds that are smaller molecules than the thermoplastic polymer. The smaller functionalized compounds may include functional groups such as primary amines, secondary amines, thiols, and / or phenolic compounds. The smaller functionalized compounds may be provided in the resin composition, thereby allowing for tuning of the resin properties, including, but not limited to, properties such as thermal stability. Formulating may be done by powder dry mixing, melt mixing, or mixing in solution.

[0052] In view of the high reactivity with benzoxazine to form a self-healing resin, the diamine may be particularly suitable for the ring-opening reaction of the benzoxazine moiety with the diamine. Such diamines include aromatic diamine compounds having 6 to 27 carbon atoms, such as bis[4-(3-aminophenoxy)phenyl]sulfone (BAPS-m), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS-p), 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene (2,4-TDA), 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenylether (ODA), 3,4'-diaminodiphenylether, and the like. (DPE), 3,3'-dimethyl-4,4'-diaminobiphenyl (TB), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 3,7-diamino-dimethyldibenzothiophene-5,5-dioxide (TSN), 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-bis(4-aminophenyl)sulfide (ASD), 4,4'-diaminodiphenylsulfone (ASN), 4,4'-diaminobenzanilide (DABA), 1,n-bis(4-aminophenoxy)alkane (n = 3, 4 or 5, DAnMG), 1,3-bis(4-aminophenoxy)-2,2-dimethylpropane (DANPG), 1,2-bis[2-(4-aminophenoxy)ethoxy]ethane (DA3EG), 1,5-bis(4-aminophenoxy)pentane (DA5MG), 1,3-bis(4-aminophenoxy)propane (DA3MG), 9,9-bis(4-aminophenyl)fluorene (FDA), 5(6)-amino-1-(4-aminomethyl)-1,3,3-trimethylindane, 1,4-bis(4-aminophenoxy)benzene (TPE-Q or APB-144), 1,3-bis(4-aminophenoxy)benzene (TPE-R or APB-134 or RODA), 1,3-bis(3-aminophenoxy)benzene (APB or APB-133)), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis(4-aminophenoxyphenyl)propane (BAPP), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), 3,3'-dicarboxy-4,4'-diaminodiphenylmethane (MBAA), or 4,6-dihydroxy-1,3-phenylenediamine (known as 4,6-diaminoresorcinol), 3,3'-dihydroxy-4,4'-diaminobiphenyl (HAB) and 3,3',4,4'-tetraaminobiphenyl (TAB); aliphatic or alicyclic diamine compounds having 6 to 24 carbon atoms, e.g. 1,6 -hexamethylenediamine (HMD), 1,8-octamethylenediamine (OMDA), 1,9-nonamethylenediamine, 1,12-dodecamethylenediamine (DMDA), 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 4,4'-dicyclohexylmethanediamine and cyclohexanediamine; silicone-based diamine compounds, such as 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and polydimethylsiloxane (PDMS); or combinations thereof. In one or more embodiments, the aromatic compounds (VIII) or (IX) (wherein each R9 is independently selected from H, CH3, or halogen, and n is an integer ranging from 1 to 7), and hexamethylenediamine (X) (wherein R, 10 is independently selected from H or a halogen, and n is an integer ranging from 1 to 15), one or more flexible comonomers may be used, including alkyl diamines such as:

[0053] [ka]

[0054] Each of R11 and R11' may independently represent a functional group selected from a primary amine, a secondary amine, a thiol, or a phenolic compound.

[0055] In some embodiments, the self-repairing resin composition may include at least one optional additive. The optional additive may include inorganic compounds, organic compounds, thermosetting resins, and combinations thereof. Such additives may increase supramolecular interactions such as hydrogen bonding, host-guest interactions, π-π interactions, and metal-ligand interactions.

[0056] In some embodiments, the optional additive may include an inorganic compound. The inorganic compound may be a metal complex with a halide (such as, for example, fluoride, chloride, bromide, iodide, and combinations thereof). The inorganic compound may be a metal complex with acetate, phosphate, perchlorate, sulfate, triflate, fluoroborate, nitrate, phenolate, and carbonate. The inorganic compound may include metals of iron, aluminum, zinc, manganese, cobalt, copper, nickel, magnesium, calcium, and combinations thereof. In some embodiments, the inorganic compound may be AlCl3, FeCl3, ZnCl2, and combinations thereof.

[0057] Inorganic compounds may be included in amounts ranging from 1 to 25 phr. In some embodiments, the self-healing resin may include inorganic compounds in ranges having a lower limit of one of 1, 3, 5, or 8 phr (parts per hundred resin) of any additive, and an upper limit of one of 10, 15, 20, and 25 phr, any lower limit may be paired with any mathematically compatible upper limit.

[0058] In one or more embodiments, the optional additive may include an organic compound. In certain embodiments, the organic compound may include a carboxylic acid compound, a phenolic compound, and a combination thereof. In some embodiments, the organic compound may be benzoic acid, hydroxybenzoic acid, salicylic acid, 2,4-hexadienoic acid, naphthoic acid, hydroxynaphthoic acid, 4,4'-biphenol, bisphenol-A, bisphenol-F, bisphenol-S, 4,4'-dihydroxybenzophenone.

[0059] The organic compounds may be included in amounts ranging from 1 to 25 phr. In some embodiments, the self-healing resin may include organic compounds in ranges having a lower limit of one of 1, 3, 5, or 8 phr (parts per hundred resin) of any additive, and an upper limit of one of 10, 15, 20, and 25 phr, any lower limit may be paired with any mathematically compatible upper limit.

[0060] In one or more embodiments, the optional additives may include thermosetting resins (e.g., epoxy resins, bismaleimides, and / or cyanate compounds, etc.). Commonly used bismaleimides and cyanate ester compounds known in the art may be suitable. Examples of epoxy compounds may include, but are not limited to, cycloaliphatic epoxy compounds, aromatic phenyl group-based epoxy compounds, and polyglycidyl epoxy compounds (e.g., polyglycidyl ethers or polyglycidyl esters, etc.).

[0061] Thermosetting resins may be included in amounts ranging from 1 to 15 phr. In some embodiments, the self-healing resin may include epoxy compounds in ranges having a lower limit of one of 1, 2, 3, 5, or 7 phr (parts per hundred resin) of any additive, and an upper limit of one of 8, 10, 12, and 15 phr, any lower limit may be paired with any mathematically compatible upper limit.

[0062] Any of the optional additives mentioned above may be used alone or in combination.

[0063] In one or more embodiments, the self-healing resin composition may be obtained by a melt polymerization process. In some embodiments, melt polymerization may be used for the synthesis of the self-healing resin composition because no solvent is required and the reaction time is significantly reduced compared to solution phase polymerization. Furthermore, melt polymerization may be advantageous because purification may not be required after the polymerization is completed. In one or more embodiments, the melt polymerization may include ring-opening of the BZ compound to form the self-healing resin composition. In such an embodiment, the BZ compound is ring-opened by reaction with the terminal amine group of the thermoplastic polymer.

[0064] The melt polymerization of one or more embodiments may have a temperature in the range of approximately 50 to 130° C. In some embodiments, the melt polymerization may have a temperature in the range having a lower limit of one of 50, 55, 60, 65, 70, 75, 80, 85, and 90° C. and an upper limit of one of 95, 100, 105, 110, 115, 120, 125, and 130° C., any lower limit may be paired with any mathematically compatible upper limit.

[0065] The melt polymerization of one or more embodiments may be carried out for a total time ranging from approximately 1 to 10 hours. In some embodiments, the melt polymerization may be carried out for a total time range having a lower limit of one of 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 hours, and an upper limit of one of 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, and 10 hours, any lower limit may be paired with any mathematically compatible upper limit.

[0066] In one or more embodiments, the melt polymerization may include a molar ratio (thermoplastic polymer to BZ compound) of 1:10 to 10:1. In some embodiments, the molar ratio of thermoplastic polymer to BZ compound may be a range having a lower limit of one of 1:10, 1:8, 1:5, 1:3, 1:2, 1:1, and 2:1, and an upper limit of one of 1:2, 1:1, 2:1, 3:1, 5:1, 8:1, and 10:1, where any lower limit may be paired with any mathematically compatible upper limit.

[0067] In one or more embodiments, the melt polymerization may include any additive in an amount ranging from 1 to 50 phr (parts per hundred resin). In some embodiments, the melt polymerization may include any additive amount in a range having a lower limit of one of 1, 5, 10, 15, 20, and 25 phr, and an upper limit of one of 30, 35, 40, 45, and 50 phr, where any lower limit may be paired with any mathematically compatible upper limit.

[0068] In one or more embodiments, melt polymerization may include mixing the raw materials (e.g., thermoplastic polymer, BZ compound, and other components of the above-mentioned composition) by solvent or melt mixing at high solids. In one or more embodiments, melt polymerization includes heating, which may be performed using, but is not limited to, an oven, an extruder, a hot plate, an oil bath, a hot press, an autoclave, and the like. In one or more embodiments, melt polymerization may be performed under, but is not limited to, standard atmospheric pressure, vacuum, and an inert atmosphere, such as argon or nitrogen gas. In one or more embodiments, melt polymerization by heating may be performed under, but is not limited to, a flow of air, or under an inert gas, such as argon or nitrogen.

[0069] Solution-based synthesis methods may also provide the same self-healing resin composition. However, solution methods are highly dependent on the solid content of the feedstock for polymerization and may require much longer reaction times. In solution-based polymerization, the solid content of the feedstock should be high enough to drive the reaction. In one or more embodiments, the solid content of the feedstock in the solvent may be in an amount ranging from 25 to 90 percent by weight. In some embodiments, the solid content in the solvent may include a lower limit of one of 25, 30, 35, 40, 45, and 50, and an upper limit of one of 55, 60, 65, 70, 75, 80, 85, and 90, and any lower limit may be paired with any mathematically compatible upper limit.

[0070] A self-healing resin according to one or more embodiments of the present disclosure may include units derived from thermoplastic polymers in an amount ranging from 50 to 95 wt% (weight percent). In some embodiments, the self-healing resin may include units derived from thermoplastic polymers in an amount ranging from a lower limit of one of 50, 55, 60, and 65 wt% and an upper limit of one of 70, 75, 80, 85, 90, and 95 wt%, any lower limit may be paired with any mathematically compatible upper limit.

[0071] A self-healing resin according to one or more embodiments of the present disclosure may include units derived from BZ compounds in an amount ranging from 5 to 50% by weight. In some embodiments, the self-healing resin may include units derived from BZ compounds in an amount ranging from one of 5, 10, 15, 20, 25, and 30% by weight lower limit and one of 35, 40, 45, and 50% by weight upper limit, any lower limit may be paired with any mathematically compatible upper limit.

[0072] A self-healing resin according to one or more embodiments of the present disclosure may include a total amount of optional additives in an amount ranging from 1 to 50 phr. In some embodiments, the self-healing resin may include an amount of optional additives within a range having a lower limit of one of 1, 5, 10, 15, 20, and 25 phr, and an upper limit of one of 30, 35, 40, 45, and 50 phr, where any lower limit may be paired with any mathematically compatible upper limit.

[0073] A self-healing resin according to one or more embodiments of the present disclosure may have an unreacted BZ compound content of about 5-40 wt. %. In some embodiments, the self-healing resin may include an unreacted BZ compound content having a lower limit of one of 5, 10, 15, and 20 wt. % and an upper limit of one of 25, 30, 35, and 40 wt. %, any lower limit may be paired with any mathematically compatible upper limit.

[0074] A self-healing resin according to one or more embodiments of the present disclosure may have a weight average molecular weight (Mw) in the range of about 5 to 100 kilodaltons (kDa). In some embodiments, the Mw of the self-healing resin may be in a range having a lower limit of one of 5, 10, 20, 40, and 50 kDa and an upper limit of one of 60, 70, 80, 90, 100 kDa, any lower limit may be paired with any mathematically compatible upper limit.

[0075] In one or more embodiments, the polymer formed by polymerization of the self-healing resin described above may include the above-mentioned terminal functional groups, such as benzoxazine moieties, on both end caps of the polymer. Examples of such structures are shown in Figures 1A and 1B. In one or more embodiments, the polymer formed by polymerization of the self-healing resin described above may include the above-mentioned terminal functional groups, such as amine moieties, on both end caps of the polymer. Examples of such structures are shown in Figure 1C.

[0076] An exemplary self-healing resin according to one or more embodiments of the present disclosure may have the structure shown in Figures 1A, 1B, and 1C. The portion labeled "TP" represents the thermoplastic polymer described above.

[0077] As shown in Figures 1A, 1B and 1C, the BZ moiety is ring-opened by reaction with the terminal amine group. Furthermore, after undergoing the ring-opening reaction, the unit from the BZ compound contributes phenolic and secondary amine functional groups to the overall polymer structure. Such functional groups can contribute to hydrogen bonding within the polymer structure and improve the self-healing properties.

[0078] The self-healing resin according to one or more embodiments of the present disclosure may be cured to form an article (e.g., a film or coating, etc.). The self-healing resin may be cured in a variety of ways. These may include, but are not limited to, cure cycles, including by external stimuli selected from heat, ultraviolet radiation, microwave radiation, moisture, etc., solution casting, hot melt pressing, etc. In certain embodiments, the self-healing resin may be cured at a cure temperature of about 30 to 150° C. for a cure time of 1 hour to 7 days. The cure time and temperature may be appropriately adjusted based on the self-healing resin composition.

[0079] The self-healing resin according to one or more embodiments of the present disclosure may have a variety of applications, such as in composites or as a coating. In composites, the self-healing resin may be used as the primary matrix polymer or as an additive in a composite with a separate matrix polymer. When used as an additive, the self-healing resin may be present in an amount of up to 50% by weight. Furthermore, in one or more embodiments, when the self-healing resin is used as an additive, the primary matrix polymer may include, but is not limited to, epoxy resin, benzoxazine, polyamide, polypropylene, polysulfone, or polyphenylene sulfide.

[0080] In one or more embodiments, the self-healing resin can be formulated as a composition including additives, toughening agents made from thermoplastic resins, thermosetting resins, inorganic compounds, organic compounds, and the like. Blending can be done by powder dry mixing, melt mixing, or mixing in solution. The shape of both the additives and toughening agents can include, for example, particles including, but not limited to, plates or fibers. One or more additives, toughening agents, and fibers can be formulated with the curable composition. For example, one or more thermoplastic resins can be formulated with the self-healing resin. Such thermoplastic resins can include, but are not limited to, poly(ether ketones), poly(ether ether ketones), poly(phenylene sulfides), poly(ether imides), polycarbonates, polysulfones, and the like. In another example, one or more thermosetting resins can be formulated with the curable composition and co-cured with heat. Such thermosetting resins can include, but are not limited to, epoxy resins, benzoxazines, bismaleimides, cyanate esters, and the like. It is also envisioned that thermoplastic and thermosetting resins can be used with the self-healing resins of the present disclosure. In one or more embodiments, inorganic compounds, organic compounds, and combinations thereof can be used with the self-healing resin composition to lower the curing temperature. For example, the organic compounds can include, but are not limited to, functional groups such as amino groups, imidazole groups, carboxyl groups, hydroxyl groups, and sulfonyl groups.

[0081] Self-healing resins according to one or more embodiments of the present disclosure may be useful for forming structural composites in many applications, including, but not limited to, aerospace, automotive, and marine applications. A break in a structural part in an aerospace, automotive, or marine application may result in failure of the part, and thus the self-healing properties may be particularly useful in such parts. However, the resins currently described are not limited to such articles.

[0082] In forming a coating or adhesive layer, application of the formulated coating may be by conventional methods such as spraying, roller coating, dip coating, etc. The coated system may then be cured, for example, by baking.

[0083] Articles made from self-healing resin according to one or more embodiments of the present disclosure may exhibit self-healing properties. In certain embodiments, the self-healing resin may repair breaks at room temperature or at elevated temperatures without the need for other additives or fillers. As used herein, a break may be a cut, crack, puncture, scratch, or other similar physical deformation in the resin. As used herein, repair means that the break at least partially re-forms the structure it previously presented.

[0084] In one or more embodiments, an article having a break can be self-healed by maintaining the article at a predetermined temperature for a predetermined time so that the break is repaired. In one or more embodiments, the self-healing temperature can be in a range from about ambient temperature to 175°C. In some embodiments, the self-healing temperature can be in a range having a lower limit of any of ambient temperature, 30, 50, 60, and 90°C, and an upper limit of any of 100, 125, 150, and 175°C, any lower limit can be paired with any mathematically compatible upper limit. In one or more embodiments, the self-healing time can be in a range from about 30 minutes to several days. In some embodiments, the self-healing time can be in a range having a lower limit of any of 0.5, 1.0, 1.5, 2.0, 2.5, 3, 5, or 10 hours, and an upper limit of any of 10, 7, 5, 2, and 1 day, any lower limit can be paired with any mathematically compatible upper limit. If a higher self-healing temperature is used, generally a shorter self-healing time is required.

[0085] Without wishing to be limited to any particular mechanism or theory, it is believed that high dynamic mobility and supramolecular interactions in the polymer structure may contribute to the excellent self-healing properties. As explained above, the self-healing resin may include hydrogen bonding interactions from the phenolic groups and secondary amine groups on the ring-opening di-BZ units. Hydrogen bonds may also be provided from the thermoplastic polymer units. The use of additives such as metal complexes may provide metal-ligand interactions in the polymer structure and improve the self-healing properties. Epoxy resins may be useful additives for self-healing properties because they can undergo ring-opening reactions with the phenolic groups present in the di-BZ units in the polymer. Such ring-opening reactions generate alkyl hydroxyls. They may also contribute to hydrogen bonding within the polymer. However, the use of excess amounts of epoxy resins may result in crosslinking with the phenolic groups. They may reduce optimal hydrogen bonding within the polymer structure and reduce the self-healing properties. The combination of epoxy resins with metal complexes may provide improved self-healing through favorable metal-ligand interactions between the metal ions and phenolic groups in the polymer and may prevent unfavorable crosslinking of the epoxy resin with the phenol. Additives such as phenolic compounds and carboxylic acids can also increase hydrogen bonding in the structure and contribute to the self-healing properties.

[0086] [Example] The following examples are merely illustrative and should not be construed as limiting the scope of the disclosure.

[0087] 〔material〕 Bisamine-type benzoxazine (product name: Pd) was obtained from Shikoku Chemical Industry Co., Ltd. O,O'-bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol (product name: Jeffamine® ED-2003) was purchased from Sigma-Aldrich. Aluminum chloride hexahydrate, [Al(H2O)6]Cl3, and methanol were obtained from VWR. THF and 1,3-dioxolane were purchased from Beantown Chemicals. Bisphenol-A diglycidyl ether epoxy resin (product name: Epon® Resin 828) was obtained from Polysciences.

[0088] Synthesis of PE-BZ (Example 1) 5.00 g of Pd (11.5 mmol) and 24.17 g (12.1 mmol) of Jeffamine ED-2003 were added to the flask and stirred at 90° C. for about 4 hours. As the reaction proceeded, an increase in the viscosity of the mixture was observed. The resulting product was cooled to room temperature and refrigerated to prevent undesired crosslinking. The resulting product is called PE-BZ. The melting point of this resin is about 30° C.

[0089] Synthesis of PE-BZ + epoxy resin and metal complex (Example 2) Stock solutions of the reactants were prepared by the following method: 5.525 g of PE-BZ was dissolved in 15 mL of 1,3-dioxolane by stirring for 2 hours with gentle heating. 325 mg of Epon® Resin 828 (hereafter referred to as "epoxy resin") was dissolved in 6 mL of THF by stirring for 60 minutes. 182 mg of AlCl3 was dissolved in 2 mL of methanol by stirring for 60 minutes.

[0090] PE-BZ, as described in Example 1, was mixed with a given amount of epoxy stock solution, and optional AlCl. The amounts of each component are listed in Table 1 below.

[0091] [Table 1]

[0092] First, the PE-BZ solution was vigorously stirred while the desired amount of epoxy solution was added. Then, if applicable, the AlCl3 solution was slowly added with vigorous stirring. After all the metal complex solutions had been added, the mixture was stirred for approximately 1 hour.

[0093] [Film formation (Example 3)] Membranes were prepared from the samples of Examples 1 and 2. PE-BZ membrane (i.e., Sample 1) was prepared by curing PE-BZ in air at 200°C for 30 minutes. Membranes of Samples 2 and 3 were prepared by curing in air at the following temperatures and times: 30°C for 2 days, followed by 60°C for 1 hour, followed by 90°C for 5 hours, followed by 120°C for 1.5 hours. The membrane of Sample 2 was further treated at 200°C for 30 minutes to obtain ring-open residual di-BZ. This treatment is not necessary for Sample 3 because AlCl3 acts as a catalyst at low temperatures.

[0094] [High-temperature self-repair test (Example 4)] The membranes of Samples 1-3 were prepared according to Example 3 and cut into pieces of approximately 1 cm x 1 cm. Two cuts were then made in the membrane using a razor blade. The membranes were then heated to 125°C or 150°C and held at that temperature for 1-2 hours. Macro photographs were taken before and after heating.

[0095] [Room temperature self-repair test (Example 5)] The membrane of Sample 3 was prepared according to Example 3 and cut into pieces of approximately 1 cm x 1 cm. The membrane was then cut to completely cut, separating the membrane into two pieces. The pieces were placed in physical contact with each other and a small weight was placed on top of the membrane to ensure uniform contact. The membrane was left for 5 days. Photographs and close-ups were taken before and after the 5th day.

[0096] Similarly, a 1 cm x 0.25 cm film strip of Sample 1 had two complete cuts made along its length. The pieces were placed in physical contact with each other and a small weight was placed on top of the film to ensure uniform contact. The film was left for 2.5 days. A close-up was taken after 2.5 days.

[0097] [Thermal stability (Example 5)] The thermal stability of the PE-BZ resin made according to Example 1 was tested by heating the resin to 200° C. in air and measuring the weight loss after 2 hours at 200° C. A weight loss of less than 1% by weight was observed for the PE-BZ resin. As a comparison, the same thermal stability test was performed on Jeffamine® ED-2003 polymer. A weight loss of 14% by weight was observed after 2 hours at 200° C. in air, indicating enhanced thermal stability of the PE-BZ resin compared to the Jeffamine® ED-2003 polymer.

[0098] [Results and Discussion] FIG. 2A shows Sample 1 with cuts according to Example 4. FIG. 2B shows Sample 1 after heating to 150° C. for 1.5 hours. As shown, the cuts in the film are no longer evident after heating, indicating that the film has almost completely healed. Notably, this film was subsequently cut and self-healed three times. Without wishing to be limited to a particular mechanism or theory, it is believed that the supramolecular interactions present in PE-BZ (e.g., hydrogen bonding between the phenolic groups and the ether polymer backbone) together with sufficient molecular mobility allow the polymer to self-heal.

[0099] Figure 3A shows Sample 2 with a cut according to Example 4. Figure 3B shows Sample 2 after heating to 150°C for 2 hours. There appears to be some healing in this sample; however, it is not as significant as the healing in Sample 1. Without wishing to be bound to a particular mechanism or theory, it is believed that reaction of the epoxy resin with the phenolic groups in PE-BZ may result in crosslinking, reducing molecular mobility as well as the favorable hydrogen bonding properties within the PE-BZ structure, thereby reducing its self-healing properties.

[0100] Figure 4A shows Sample 3 with a cut according to Example 4. Figure 4B shows Sample 3 after heating to 125°C for 1 hour. This sample appears to have almost completely healed in a relatively short time and at a relatively low temperature. Without wishing to be limited to a particular mechanism or theory, it is believed that AlCl3 may prevent cross-linking between the phenolic and the epoxy resin and provide a metal-ligand interaction to provide better self-healing.

[0101] Figure 5A is a photograph of Sample 3 having a cut according to Example 5. Figure 5B is a photograph of the same sample after about 5 days at room temperature. As shown, the sample exhibits nearly complete self-healing at room temperature.

[0102] Figure 6A is a close-up of the sample shown in Figure 5A. Complete severing of the membrane can be seen. Figures 6B and 6C are close-ups of the sample in Figure 5B. As can be seen, the sample appears to have almost completely self-healed at room temperature.

[0103] Figure 7A shows Sample 1 according to Example 5 with a cut in the process of healing. Figures 7B and 7C are enlarged views of the cut and repaired part of Figure 7A. The healing process after 2.5 days is observed. Once completely cut, the film was put together by self-healing at room temperature.

[0104] Although only a few exemplary embodiments have been detailed above, those skilled in the art will readily appreciate that many variations in the exemplary embodiments are possible without substantially departing from the present invention. Accordingly, all such variations are intended to fall within the scope of the present disclosure as defined by the following claims. In the claims, the means-plus-function clauses are intended to cover the structures described herein as performing the described functions, and equivalent structures as well as structural equivalents. Thus, while a nail and a screw may not be structurally equivalent in that they employ a cylindrical surface to fasten wooden parts together, while a screw employs a helical surface, they may be equivalent structures insofar as they fasten wooden parts together. It is the express intent of the applicants not to invoke 35 USC § 112, paragraph 6, to any limitation of the claims herein, except where the claims expressly use the words "means for" with the relevant function. [Brief description of the drawings]

[0105] [Figure 1A] FIG. 1A is an exemplary self-healing resin according to one or more embodiments of the present disclosure. [Figure 1B] FIG. 1B is an exemplary self-healing resin according to one or more embodiments of the present disclosure. [Figure 1C] FIG. 1C is an exemplary self-healing resin according to one or more embodiments of the present disclosure. [Figure 2A] FIG. 2A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure. [Figure 2B] FIG. 2B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 3A] FIG. 3A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure. [Figure 3B] FIG. 3B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 4A] FIG. 4A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure. [Figure 4B] FIG. 4B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 5A] FIG. 5A is a photograph of a polymer having a cleavage according to one or more embodiments of the present disclosure. [Figure 5B] FIG. 5B is a photograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 6A] FIG. 6A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure. [Figure 6B] FIG. 6B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 6C] FIG. 6C is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 7A] FIG. 7A is a micrograph of a polymer having a cleavage according to one or more embodiments of the present disclosure. [Figure 7B] FIG. 7B is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure. [Figure 7C] FIG. 7C is a micrograph of a polymer that has undergone self-healing in accordance with one or more embodiments of the present disclosure.

Claims

1. A polymer formed from the reaction between (a) a thermoplastic polymer having terminal functional groups and (b) a benzoxazine compound, a polymer, wherein the terminal functional group is selected from the group consisting of a primary amine, a secondary amine, a thiol, a phenol, or a substituted phenol containing additional functional groups, and combinations thereof; and 1 to 15 phr of a thermosetting resin selected from the group consisting of epoxy resins, bismaleimide resins, cyanate ester resins, and combinations thereof; The thermoplastic polymer is a polyether having a structure represented by formula (I) or (II): 【Chemistry 1】 In formula (I), y is 1 to 40, x+z is 1 to 8, R1 and R1' are independently selected from primary amines, secondary amines, thiols, and phenols or substituted phenols containing additional functional groups; 【Chemistry 2】 A self-healing resin composition, wherein in formula (II), x is from 2 to 70, and R2 and R2' are independently selected from primary amines, secondary amines, thiols, or phenols or substituted phenols containing additional functional groups.

2. 2. The self-healing resin composition of claim 1, wherein the thermoplastic polymer has a weight average molecular weight (Mw) of from 500 to 4,000 Da (Daltons).

3. The self-repairing resin composition according to claim 1, wherein the benzoxazine compound is a benzoxazine having a structure represented by formula (V): 【Chemistry 3】

4. The self-repairing resin composition according to claim 1, wherein the benzoxazine compound is a benzoxazine having a structure represented by formula (VII): 【Chemistry 4】

5. AlCl ３ , FeCl ３ , ZnCl ２ 10. The self-repairing resin composition of claim 1, further comprising an inorganic compound selected from the group consisting of:

6. 6. The self-repairing resin composition of claim 5, comprising from 1 to 25 phr of said inorganic compound.

7. The self-repairing resin composition of claim 1 , further comprising an aromatic diamine.

8. 2. The self-healing resin composition of claim 1, wherein the polymer comprises from 50 to 95% by weight of units derived from the thermoplastic polymer.

9. The self-repairing resin composition of claim 1 , wherein the polymer contains from 5 to 50% by weight of units derived from the benzoxazine compound.

10. 1. A method of forming a self-repairing resin composition, comprising: (a) reacting a benzoxazine compound with (b) a thermoplastic polymer having terminal functional groups by melt polymerization to form a first polymer, the terminal functional group is selected from the group consisting of a primary amine, a secondary amine, a thiol, a phenol, or a substituted phenol containing additional functional groups, and combinations thereof; and mixing said first polymer with 1 to 15 phr of a thermosetting resin selected from the group consisting of epoxy resins, bismaleimide resins, cyanate ester resins, and combinations thereof; The thermoplastic polymer is a polyether having a structure represented by formula (I) or (II): 【Chemistry 5】 In formula (I), y is 1 to 40, x+z is 1 to 8, R1 and R1' are independently selected from primary amines, secondary amines, thiols, and phenols or substituted phenols containing additional functional groups; 【Chemistry 6】 The method of claim 1, wherein in formula (II), x is from 2 to 70, and R2 and R2' are independently selected from a primary amine, a secondary amine, a thiol, or a phenol or a substituted phenol containing additional functional groups.

11. 11. The method of claim 10, wherein the melt polymerization is at a temperature ranging from 50 to 130°C.

12. 11. The method of claim 10, wherein the melt polymerization has a time ranging from 1 to 10 hours.

13. 11. The method of claim 10, wherein the thermoplastic polymer and the benzoxazine compound are present in a molar ratio of from 1:10 to 10:

1.

14. 1. A method for self-repairing an article, comprising: the article having a break therein; The method includes maintaining the article at a temperature from ambient to 175° C. for 0.5 hours to 10 days to allow the break to heal; The article is formed by mixing a polymer with 1 to 15 phr of a thermosetting resin, the polymer being a polymer resulting from a reaction between (a) a thermoplastic polymer having terminal functional groups and (b) a benzoxazine; the terminal functional group is selected from the group consisting of a primary amine, a secondary amine, a thiol, a phenol, or a substituted phenol containing additional functional groups, and combinations thereof; the thermosetting resin is selected from the group consisting of epoxy resins, bismaleimide resins, cyanate ester resins, and combinations thereof; The thermoplastic polymer is a polyether having a structure represented by formula (I) or (II): 【Chemistry 7】 In formula (I), y is 1 to 40, x+z is 1 to 8, R1 and R1' are independently selected from primary amines, secondary amines, thiols, and phenols or substituted phenols containing additional functional groups; 【Chemistry 8】 The method of claim 1, wherein in formula (II), x is from 2 to 70, and R2 and R2' are independently selected from a primary amine, a secondary amine, a thiol, or a phenol or a substituted phenol containing additional functional groups.

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