Thiol-functionalized catechol adducts and compositions thereof

Abstract

Disclosed herein are thiol-functionalized catechol adducts comprising a catechol moiety incorporated into a backbone of a polythiol. Also disclosed are coating compositions comprising: a thiol-functionalized catechol adduct; a polyepoxide; and an accelerator. Also disclosed are methods of coating a substrate comprising. Also disclosed are substrates comprising a coating on a surface thereof, the coating formed from one of the coating compositions. Also disclosed are uses of the thiol-functionalized catechol adduct and the compositions.

Description

THIOL-FUNCTIONALIZED CATECHOL ADDUCTS AND COMPOSITIONS THEREOF CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application No. 63 / 513,276, filed July 12, 2023, incorporated by reference herein in its entirety. FIELD

[0002] The present disclosure relates to thiol-functional catechol adducts, compositions comprising thiol-functional catechol adducts, and uses of thiol-functional catechol adducts. BACKGROUND

[0003] Sealants useful in aerospace and other applications must satisfy demanding mechanical, chemical, and environmental requirements. For example, it is desirable that aerospace sealants function over a temperature range such as −67°F to 360°F and exhibit fuel resistance.

[0004] Aerospace vehicles often include lightweight surfaces made from aluminum and titanium alloys. Sulfur-containing prepolymers having improved adhesion to metal surfaces and that meet other performance requirements for use in aerospace and other applications are desired. SUMMARY

[0005] Disclosed herein are thiol-functionalized catechol adducts comprising a catechol moiety incorporated into a backbone of a polythiol.

[0006] Also disclosed are coating compositions comprising: one of the thiol- functionalized catechols disclosed herein; a polyepoxide; and an accelerator.

[0007] Also disclosed are coating compositions comprising: a first component comprising one of the thiol-functionalized catechols disclosed herein; a second component comprising a polyepoxide; and an accelerator.

[0008] Also disclosed are methods of coating a substrate comprising applying one of the coating compositions disclosed herein to a portion of a surface of the substrate.

[0009] Also disclosed are substrates comprising a coating on a surface thereof, the coating formed from one of the coating compositions disclosed herein. DETAILED DESCRIPTION

[0010] For purposes of this detailed description, it is to be understood that the disclosure may assume alternative variations and step sequences, except where expressly specified to thecontrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0011] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.

[0012] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

[0013] As used herein, “including,” “containing” and like terms are understood in the context of this application to be synonymous with “comprising” and are therefore open-ended and do not exclude the presence of additional undescribed or unrecited elements, materials, ingredients or method steps. As used herein, “consisting of” is understood in the context of this application to exclude the presence of any unspecified element, ingredient, or method step. As used herein, “consisting essentially of” is understood in the context of this application to include the specified elements, materials, or ingredients or method steps “and those that do not materially affect the basic and novel characteristic(s)” of what is being described. As used herein, open- ended terms include closed terms such as consisting essentially of and consisting of.

[0014] In this application, the use of the singular includes the plural, and the plural encompasses the singular, unless specifically stated otherwise. For example, although referenceis made herein to “a” polythiol or “a” catechol, a combination (i.e., a plurality) of these components may be used.

[0015] In addition, in this application, the use of “or” means “and / or” unless specifically stated otherwise, even though “and / or” may be explicitly used in certain instances.

[0016] As used herein, the terms “on,” “onto,” “applied on,” “applied onto,” “formed on,” “deposited on,” “deposited onto,” and the like mean formed, overlaid, deposited, or provided on, but not necessarily in contact with, a substrate surface. For example, a composition “applied onto” a substrate surface does not preclude the presence of one or more other intervening coating layers or films of the same or different composition located between the composition and the substrate surface.

[0017] As used herein, a “coating composition” refers to a composition, e.g., a solution, mixture, paste, or a dispersion, that, is capable of producing a coating on a portion of a substrate surface. “Coating,” as used herein, includes films, layers and the like.

[0018] As used herein, a “sealant” or a “sealant composition” refers to a coating composition, e.g., a solution, mixture, paste, or a dispersion that forms a cured sealant that has the ability to resist atmospheric conditions such as temperature and moisture gradients and particulate matter, such as moisture and temperature and partially block the transmission of materials, such as particulates, water, fuel, and other liquids and gasses.

[0019] As further defined herein, ambient conditions generally refer to room temperature (e.g., 23ºC) and humidity conditions or temperature and humidity conditions that are typically found in the area in which the composition is applied to a substrate, e.g., at 10ºC to 40ºC and 5% to 80% relative humidity, while slightly thermal conditions are temperatures that are slightly above ambient temperature, such as 40ºC to 60ºC.

[0020] As used herein, the term “multi-component” refers to a composition in which a portion of the reactive components readily associate to form an interaction or react to form a bond (physically or chemically), and cure without activation from an external energy source, such as at ambient or slightly thermal conditions, when mixed. One of skill in the art understands that the multiple components of the composition are stored separately from each other and mixed just prior to application of the composition. Multi-component compositions include compositions comprising two or more components (a “two component” or “2K”composition), such as three components, and so forth. Optionally, the composition may be heated or baked.

[0021] As used herein, the terms “cure,” “cured,” or similar terms, means that the reactive functional groups of the components that form the composition react to form a coating, such as a film, layer, or bond. As used herein, “curing” of the curable composition refers to subjecting said composition to curing conditions leading to reaction of the reactive functional groups of the components of the composition and resulting in the crosslinking of the components of the composition and formation of a coating, such as a cured film, layer, or bond. As used herein, a “curable” composition refers to a composition that may be cured. In the case of a 2K composition, the composition is cured when the components of the composition are mixed resulting in the reaction of the reactive functional groups of the components of the composition. The curable composition may also be subjected to curing conditions such that a substantially complete cure is attained and wherein further curing results in no significant further improvement in the coating properties such as, for example, increased adhesion.

[0022] As used herein, “prepolymer” refers to a monomer or system of monomers that have been reacted to an intermediate molecular mass state and that is capable of further polymerization through reaction of reactive functional groups.

[0023] As used herein, “functional group” means specific groups of atoms within a molecule that have the potential to undergo chemical reactions under certain conditions, regardless of the other atoms in the molecule.

[0024] As used herein, “polymer” refers to oligomers, homopolymers and copolymers.

[0025] As used herein, “backbone” means the longest series of covalently bound atoms which forms the continuous chain of the polymer.

[0026] As used herein, “catechol” refers to a compound comprising the molecular formula C6H4(OH)2 and includes derivatives of catechol, such as quinone and semi-quinone, or any other derivatives comprising C6H4(OH)2. A “catechol” has the structure I:, wherein R1, R2, R3, and R4 are independently a hydrogen, a carbon nd / or a heteroatom.

[0027] As used herein, a “substituted catechol” refers to a catechol wherein at least one of R1, R2, R3, and R4 is a reactive group, such as by way of non-limiting examples, a halogen, an amine functional group, a carboxylic acid functional group, a thiol functional group, and / or an epoxy functional group.

[0028] As used herein, “thiol” refers to a compound comprising an -SH functional group. For purposes of this disclosure a polythiol includes a compound comprising at least two -SH functional groups.

[0029] As used herein, the term “accelerator” means a substance that increases the rate or decreases the activation energy of a chemical reaction in comparison to the same reaction in the absence of the accelerator. An accelerator may be either a “catalyst,” that is, without itself undergoing any permanent chemical change, or may be reactive, that is, capable of chemical reactions and includes any level of reaction from partial to complete reaction of a reactant.

[0030] As used herein, unless indicated otherwise, the term “substantially free” means that a particular material is not purposefully added to a mixture or composition, respectively, and is present only as an impurity in a trace amount of less than 5 percent by weight based on a total weight of the mixture or composition, respectively. As used herein, unless indicated otherwise, the term “essentially free” means that a particular material is present only in an amount of less than 2 percent by weight based on a total weight of the mixture or composition, respectively. As used herein, unless indicated otherwise, the term “completely free” means that a mixture or composition, respectively, does not comprise a particular material, i.e., the mixture or composition comprises 0 percent by weight of such material.

[0031] The present disclosure is directed to a thiol-functionalized catechol adduct comprising: a catechol moiety incorporated into a backbone of a polythiol. The thiol- functionalized catechol adduct may be formulated to enhance adhesion between a coating and a surface of a substrate.

[0032] The present disclosure also is directed to a coating composition comprising, or consisting essentially of, or consisting of: a thiol-functionalized catechol adduct; and a first compound comprising a first functional group that is reactive with the thiol-functionalized catechol adduct.

[0033] The present disclosure also is directed to coating compositions comprising: a first component comprising, or consisting essentially of, or consisting of, a thiol-functionalized catechol adduct; and a second component comprising, or consisting essentially of, or consisting of, a compound comprising a first functional group that is reactive with the thiol-functionalized catechol adduct. Thiol-Functionalized Catechol Adduct

[0034] The thiol-functionalized catechol adduct may comprise a catechol moiety incorporated into a backbone of a polythiol. The catechol moiety may be derived from a substituted catechol.

[0035] The thiol-functionalized catechol adduct may comprise a thiol equivalent weight of at least 200 g / eq, such as at least 400 g / eq, such as no more than 800 g / eq, such as no more than 700 g / eq, such as 200 g / eq to 800 g / eq, such as 400 g / eq to 700 g / eq.

[0036] The thiol-functionalized catechol adduct may comprise Structure I:

[0037] The thiol-functionalized catechol adduct may be formed from reactants comprising a substituted catechol and a polythiol.

[0038] Suitable substituted catechols include halogenated catechols, acid functionalized catechols, catecholamines, such as catecholamine salts, and the like. The halogenated catechol or catechol derivative may comprise a halide such as a chloride or a bromide. The halogenated catechol may comprise a monofunctional substituted catechol and / or a difunctional substituted catechol. Useful halogenated catechols include choro-dihydroxyacetophenone and / or bromo-dihydroxyacetophenon. Other useful substituted catechols include gallic acid, dopamine, dopamine hydrochloride, caffeic acid, dihydrocaffeic acid or combinations thereof.

[0039] The catechol may comprise a theoretical molecular weight of at least 170 g / mol, such as at least 180 g / mol, such as no more than 720 g / mol, such as no more than 500 g / mol, such as 170 g / mol to 720 g / mol, such as 180 g / mol to 500 g / mol.

[0040] The reactants used to form the thiol-functionalized catechol adduct may further comprise a polythiol. Suitable examples of polythiol prepolymers include those described below.

[0041] The polythiol may comprise a theoretical thiol equivalent weight of at least 175 g / eq, such as at least 200 g / eq, such as no more than 550 g / eq, such as no more than 350 g / eq, such as 175 g / eq to 550 g / eq, such as 200 g / eq to 350 g / eq.

[0042] A molar ratio of the polythiol to the catechol may be at least 2:1, such as at least 3:1, such as no more than 6:1, such as no more than 5:1, such as 2:1 to 6:1, such as 3:1 to 5:1.

[0043] The thiol-functionalized catechol may be formed according to Reaction Scheme (I):

[0044] The thiol-functionalized catechol may be used as an adhesion promoter.Coating Compositions

[0045] The present disclosure also is directed to a coating composition comprising, or consisting essentially of, or consisting of: one of the thiol-functionalized catechol adducts disclosed herein; and a first compound comprising a first functional group that is reactive with the thiol-functionalized catechol adduct.

[0046] Also disclosed are coating compositions comprising: a first component comprising, or consisting essentially of, or consisting of, one of the thiol-functionalized catechol adducts disclosed herein; and a second component comprising, or consisting essentially of, or consisting of, a compound comprising a first functional group that is reactive with the thiol- functionalized catechol adduct. The second component optionally may further comprise a second functional group. The first component and / or the second component may further comprise a second compound comprising a third functional group reactive with the thiol- functionalized catechol adduct and / or the second functional group.

[0047] The coating compositions optionally may comprise any of the additional optional components disclosed herein.

[0048] A first component may comprise, or consist essentially of, or consist of, a thiol- functionalized catechol adduct. The first component optionally may comprise a prepolymer in addition to the thiol-functionalized catechol adduct, an accelerator, a filler, and / or an additive such as an adhesion promoter in addition to the functionalized catechol adduct.

[0049] Suitable examples of the thiol-functionalized catechol adduct include those described above. The composition may comprise the thiol-functionalized catechol adduct in an amount of at least 1 percent by weight based on total weight of the composition, such as at least 2.5 percent by weight, such as no more than 20 percent by weight, such as no more than 15 percent by weight, such as 1 percent by weight to 20 percent by weight, such as 2.5 percent by weight to 15 percent by weight.

[0050] Suitable examples of polythiol prepolymer in addition to the thiol-functionalized catechol adduct include those described below. Such a prepolymer may comprise a thiol equivalent weight of at least 500 g / eq, such as at least 1000 g / eq, such as no more than 3000 g / eq, such as no more than 2500 g / eq, such as 500 g / eq to 3000 g / eq, such as 1000 g / eq to 2500 g / eq.

[0051] The coating composition may comprise the polythiol prepolymer in addition to the thiol-functionalized catechol adduct in an amount of at least 40 percent by weight based on total weight of the composition, such as at least 45 percent by weight, such as no more than 80 percent by weight, such as no more than 75 percent by weight, such as 40 percent by weight to 80 percent by weight, such as 45 percent by weight to 75 percent by weight.

[0052] The coating composition may further comprise a polyepoxide. The polyepoxide may be in a second component of the coating composition. The coating composition and / or a second component of the composition, optionally may further comprise an accelerator, a filler, and / or an additive such as an adhesion promoter in addition to the thiol-functionalized catechol.

[0053] The coating composition may comprise the polyepoxide in an amount of at least 5 percent by weight based on total weight of the coating composition, such as at least 10 percent by weight, such as no more than 50 percent by weight, such as no more than 40 percent by weight, such as 5 percent by weight to 50 percent by weight, such as 10 percent by weight to 40 percent by weight.

[0054] The coating composition may further comprise an accelerator, a filler, and / or an additive such as an adhesion promoter in addition to the thiol-functionalized catechol.

[0055] The first component, the second component and / or third or higher components may comprise the accelerator. Suitable examples of accelerators are disclosed below. The coating composition may comprise the accelerator in an amount of at least 0.1 percent by weight, such as at least 0.2 percent by weight based on total weight of the coating composition, such as no more than 2 percent by weight, such as no more than 1.5 percent by weight, such as 0.1 percent by weight to 2 percent by weight, such as 0.2 percent by weight to 1.5 percent by weight.

[0056] The coating compositions disclosed herein may comprise a sealant composition. Thiol-Terminated Compounds

[0057] Examples of suitable thiol-terminated compounds are disclosed, for example, in U.S. Pat. No. 6,172,179, which is incorporated by reference in its entirety.

[0058] A thiol-terminated polythioether can comprise a thiol-terminated polythioether comprising the chemical structure of Formula (1): —R1—[S—(CH2)2—O—[R2—O—]m(CH2)2—S—R1]n— (1)

[0059] wherein, each R1independently comprises a C2-10n-alkanediyl group, a C3-6 branched alkanediyl group, a C6-8 cycloalkanediyl group, a C6-10 alkanecycloalkanediyl group, a divalent heterocyclic group, or a —[(CHR3)p—X—]q(CHR3)r— group, wherein each R3comprises hydrogen or methyl; each R2independently comprises a C2-10n-alkanediyl group, a C3-6 branched alkanediyl group, a C6-8 cycloalkanediyl group, a C6-14 alkanecycloalkanediyl group, a divalent heterocyclic group, or a —[(CH2)p—X—]q(CH2)r— group; each X is independently comprises O, S, or NR, wherein R comprises hydrogen or methyl; m ranges from 0 to 50; n is an integer ranging from 1 to 60; p is an integer ranging from 2 to 6; q is an integer ranging from 1 to 5; and r is an integer ranging from 2 to 10.

[0060] In Formula (1), R1can be —[(CHR3)p—X—]q(CHR3)r— wherein each X can independently comprise O and S. In Formula (1), R1can be —[(CHR3)p—X—]q(CHR3)r— each X can be O or each X can be S.

[0061] In Formula (1), R1can be —[(CH2)p—X—]q(CH2)r— wherein each X can independently comprise O and S. In Formula (1), R1can be —[(CH2)p—X—]q(CH2)r— each X can be O or each X can be S.

[0062] In Formula (1), R1can be —[(CH2)p—X—]q(CH2)r— where p can be 2, X can be O, q can be 2, r can be 2, R2can be ethanediyl, m can be 2, and n can be 9.

[0063] In Formula (1), each R1can be derived from 1,8-dimercapto-3,6-dioxaoctane (DMDO), each R1can be derived from dimercaptodiethylsulfide (DMDS), or a combination thereof.

[0064] In Formula (1), each m can independently be an integer from 1 to 3. Each m can be the same and can be 1, 2, or 3.

[0065] In Formula (1), n can be an integer from 1 to 30, an integer from 1 to 20, an integer from 1 to 10, or an integer from 1 to 5. In addition, n may be any integer from 1 to 60.

[0066] In Formula (1), each p can independently be 2, 3, 4, 5, and 6. Each p can be the same and can be 2, 3, 4, 5, or 6.

[0067] In Formula (1), each q can independently be 1, 2, 3, 4, or 5. Each q can be the same and can be 1, 2, 3, 4, or 5.

[0068] In Formula (1), each r can independently be 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0069] Each r can be the same and can be 2, 3, 4, 5, 6, 7, 8, 9, or 10. In Formula (1), each r can independently be an integer from 2 to 4, from 2 to 6, or from 2 to 8.

[0070] In Formula (1), each R2 can independently comprise a C2-10 n-alkanediyl group, a C3-6 branched alkanediyl group, or a —[(CH2)p-X-]q(CH2)r- group.

[0071] In Formula (1), each R2 can independently comprise a C2-10 n-alkanediyl group.

[0072] In Formula (1), each R2can independently comprise a —[(CH2)p—X—]q(CH2)r— group, where each X can be O or S.

[0073] A thiol-terminated polythioether can comprise a thiol-terminated polythioether of Formula (2a), a thiol-terminated polythioether of Formula (2b), or a combination thereof: HS—R1—[S—(CH2)2—O—(R2—O)m—(CH2)2—S—R1—]nSH (2a) {HS—R1—[S—(CH2)2—O—(R2—O)m—(CH2)2—S—R1—]nS—V′—}zB (2b)

[0074] wherein, each R1independently comprises C2-10alkanediyl, C6-8cycloalkanediyl, C6-14 alkanecycloalkanediyl, C5-8 heterocycloalkanediyl, or —[(CHR3)p—X—]q(CHR3)r—; wherein, p is an integer from 2 to 6; q is an integer from 1 to 5; r is an integer from 2 to 10; each R3independently comprises hydrogen or methyl; and each X independently comprises O, S, or NR, wherein R comprises hydrogen or methyl; each R2is independently comprises C1- 10 alkanediyl, C6-8 cycloalkanediyl, C6-14 alkanecycloalkanediyl, or —[(CHR3)p—X— ]q(CHR3)r—, wherein p, q, r, R3, and X are as defined as for R1; m is an integer from 0 to 50; n is an integer from 1 to 60; B represents a core of a z-valent, polyfunctionalizing agent B(—V)zwherein, z is an integer from 3 to 6; and each V is a moiety comprising a terminal group reactive with a thiol; and each —V′— is derived from the reaction of —V with a thiol.

[0075] In Formula (2a) and Formula (2b), R1can be —[(CH2)p—X—]q(CH2)r—, where p can be 2, X can be O, q can be 2, r can be 2, R2can be ethanediyl, m can be 2, and n can be 9.

[0076] In Formula (2a) and Formula (2b), R1can comprise C2-6 alkanediyl or — [(CHR3)p—X—]q(CHR3)r—.and Formula (2b), R1can be —[(CHR3)p—X—]q(CHR3)r—, X can be O or X can be S.

[0078] In Formula (2a) and Formula (2b), where R1can be —[(CHR3)p—X—]q(CHR3)r— , p can be 2, r can be 2, q can be 1, and X can be S; or wherein p can be 2, q can be 2, r can be 2, and X can be O; or p can be 2, r can be 2, q can be 1, and X can be O.

[0079] In Formula (2a) and Formula (2b), R1can be —[(CHR3)p—X—]q(CHR3)r—, and each R3can be hydrogen or at least one R3can be methyl.

[0080] In Formula (2a) and Formula (2b), each R1can be the same, or at least one R1can be different.

[0081] In Formula (2a) and Formula (2b), each m can be independently an integer from 1 to 3. Each m can be the same and can be 1, 2, or 3.

[0082] In Formula (2a) and Formula (2b), n can be an integer from 1 to 30, an integer from 1 to 20, an integer from 1 to 10, or an integer from 1 to 5. The variable n may be any integer from 1 to 60.

[0083] In Formula (2a) and Formula (2b), each p can independently be 2, 3, 4, 5, and 6. Each p can be the same and can be 2, 3, 4, 5, or 6.

[0084] In Formula (2a) and Formula (2b), each q can independently be 1, 2, 3, 4, or 5. Each q can be the same and can be 1, 2, 3, 4, or 5.

[0085] In Formula (2a) and Formula (2b), each r can independently be 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0086] Each r can be the same and can be 2, 3, 4, 5, 6, 7, 8, 9, or 10. In prepolymers of Formula (1), each r can independently be an integer from 2 to 4, from 2 to 6, or from 2 to 8.

[0087] Various methods can be used to prepare thiol-terminated polythioethers of Formula (2a) and Formula (2b). Examples of suitable thiol-terminated polythioethers, and methods for their production, are described in U.S. Pat. No. 6,172,179. Such thiol-terminated polythioethers may be difunctional, that is, linear prepolymers having two terminal thiol groups, or can be polyfunctional, that is, branched prepolymers having three or more terminal thiol groups. Suitable thiol-terminated polythioethers are commercially available, for example, as Permapol® P3.1E, from PRC-DeSoto International Inc., Sylmar, Calif.

[0088] A thiol-terminated polythioether may comprise a mixture of different thiol- terminated polythioether and the thiol-terminated polythioethers may have the same or different functionality. A thiol-terminated polythioether or combination of thiol-terminated polythioethers can have an average functionality from 2 to 6, from 2 to 4, from 2 to 3, from 2.05 to 2.8, or from 2.05 to 2.5. For example, a thiol-terminated polythioether can comprise a difunctional thiol- terminated polythioether, a trifunctional thiol-terminated polythioether, or a combination thereof.

[0089] A thiol-terminated polythioether can be prepared by reacting a polythiol and a diene such as a divinyl ether, and the respective amounts of the reactants used to prepare the polythioethers can be chosen to yield terminal thiol groups. Thus, in some cases, (n or >n, such as n+1) moles of a polythiol, such as a dithiol or a mixture of at least two different dithiols and 0.05 moles to 1 moles, such as 0.1 moles to 0.8 moles, of a thiol-terminated polyfunctionalizing agent may be reacted with (n) moles of a diene, such as a divinyl ether, or a combination of at least two different dienes, such as a combination of two different divinyl ethers. A thiol- terminated polyfunctionalizing agent can be present in the reaction mixture in an amount sufficient to provide a thiol-terminated polythioether having an average thiol functionality of from 2.05 to 3, such as from 2.1 to 2.8, or from 2.1 to 2.6. Examples of polyfunctionalizing agents are described below.

[0090] A reaction used to prepare a thiol-terminated polythioether may be catalyzed by a free radical catalyst. Suitable free radical catalysts include azo compounds, for example, azobisnitrile compounds such as azo(bis)isobutyronitrile (AIBN); organic peroxides, such as benzoyl peroxide and tert-butyl peroxide; and inorganic peroxides, such as hydrogen peroxide. The reaction can also be affected by irradiation with ultraviolet light either with or without a radical initiator / photosensitizer. Ionic catalysis methods, using either inorganic or organic bases, e.g., triethylamine, may also be used.

[0091] Suitable thiol-terminated polythioethers may be produced by reacting a divinyl ether or combination of divinyl ethers with an excess of dithiol or a combination of dithiols.

[0092] A thiol-terminated polythioether can comprise the reaction product of reactants comprising:

[0093] (a) a dithiol of Formula (3): HS—R1—SH (3)

[0094] wherein, R1comprises C2-6 alkanediyl, C6-8 cycloalkanediyl, C6- 10 alkanecycloalkanediyl, C5-8 heterocycloalkanediyl, or —[(CHR3)p—X—]q(CHR3)r—; wherein, each R3independently comprises hydrogen or methyl; each X independently comprises —O—, —S—, or —NR— wherein R comprises hydrogen or methyl; p is an integer from 2 to 6; q is an integer from 1 to 5; and r is an integer from 2 to 10; and

[0095] (b) a divinyl ether of Formula (4):CH2═CH—O—[R2—O]m—CH═CH2(4)

[0096] wherein, each R2independently comprises C1-10 alkanediyl, C6-8 cycloalkanediyl, C6-14 alkanecycloalkanediyl, or —[(CHR3)p—X—]q(CHR3)r—, wherein p, q, r, R3, and X are as defined above; and m is an integer from 0 to 50.

[0097] The reactants can further comprise (c) a polyfunctional compound such as a polyfunctional compound B(—V)z, where B, —V, and z are as defined herein.

[0098] Dithiols suitable for use in preparing thiol-terminated polythioethers include those having the structure of Formula (3): HS—R1—SH (3)

[0099] wherein, R1comprises C2-6 alkanediyl, C6-8 cycloalkanediyl, C6-10alkanecycloalkanediyl, C5-8heterocycloalkanediyl, or —[(CHR3)p—X—]q(CHR3)r—; wherein, each R3independently comprises hydrogen or methyl; each X independently comprises O, S, or NR wherein R comprises hydrogen or methyl; p is an integer from 2 to 6; q is an integer from 1 to 5; and r is an integer from 2 to 10.

[0100] In dithiols of Formula (3), R1can comprise —[(CHR3)p—X—]q(CHR3)r—.

[0101] In dithiols of Formula (3), X can comprise O and S, and thus —[(CHR3)p—X— ]q(CHR3)r— in Formula (3) can be —[(CHR3)p—O—]q(CHR3)r— or —[(CHR32)p—S— ]q(CHR3)r—. P and r can be equal, such as where p and r can be both two.

[0102] In dithiols of Formula (3), R1can comprise C2-6 alkanediyl and —[(CHR3)p—X— ]q(CHR3)r—.

[0103] In dithiols of Formula (3), R1can be —[(CHR3)p—X—]q(CHR3)r—, and X can be O, or X can be S.

[0104] In dithiols of Formula (3) where R1can be —[(CHR3)p—X—]q(CHR3)r—, p can be 2, r can be 2, q can be 1, and X can be S; or p can be 2, q can be 2, r can be 2, and X can be O; or p can be 2, r can be 2, q can be 1, and X can be O.

[0105] In dithiols of Formula (3) where R1can be —[(CHR3)p—X—]q(CHR3)r—, each R3can be hydrogen, or at least one R3can be methyl.

[0106] In dithiols of Formula (3), each R1can be derived from 1,8-dimercapto-3,6- dioxaoctane (DMDO; 2,2-(ethane-1,2-diylbis(sulfanyl))bis(ethan-1-thiol)), or each R1can bederived from dimercaptodiethylsulfide (DMDS; 2,2′-thiobis(ethan-1-thiol)), and combinations thereof.

[0107] In dithiols of Formula (3), each p can independently comprise 2, 3, 4, 5, and 6. Each p can be the same and can be 2, 3, 4, 5, or 6.

[0108] In dithiols of Formula (3) each q can independently be 1, 2, 3, 4, or 5. Each q can be the same and can be 1, 2, 3,4, or 5.

[0109] In dithiols of Formula (3), each r can independently be 2, 3, 4, 5, 6, 7, 8, 9, or 10. Each r can be the same and can be 2, 3, 4, 5, 6, 7, 8, 9, or 10. In prepolymers of Formula (1), each r can independently be an integer from 2 to 4, from 2 to 6, or from 2 to 8.

[0110] In divinyl ethers of Formula (4), each m can be independently an integer from 1 to 3. Each m can be the same and can be 1, 2, or 3.

[0111] In divinyl ethers of Formula (4), each R2 can independently comprise a C2-10 n- alkanediyl group, a C3-6 branched alkanediyl group, or a —[(CH2)p-X-]q(CH2)r- group.

[0112] In divinyl ethers of Formula (4), each R2 can independently comprise a C2-10 n- alkanediyl group.

[0113] In divinyl ethers of Formula (4), each R2 can independently comprise a — [(CH2)p-X-]q(CH2)r- group, where each X can be O or S.

[0114] In divinyl ethers of Formula (4), each R2 can independently comprise a — [(CH2)p-X-]q(CH2)r- group, where each X can be O or S, and each p can independently be 2, 3, 4, 5, and 6. Each p can be the same and can be 2, 3, 4, 5, or 6.

[0115] In divinyl ethers of Formula (4), each R2 can independently comprise a — [(CH2)p-X-]q(CH2)r- group, where each X can be O or S, and each q can independently be 1, 2, 3, 4, or 5. Each q can be the same and can be 1, 2, 3,4, or 5.

[0116] In divinyl ethers of Formula (4), each R2 can independently comprise a — [(CH2)p-X-]q(CH2)r- group, where each X can be O or S, and each r can independently be 2, 3, 4, 5, 6, 7, 8, 9, or 10, Each r can be the same and can be 2, 3, 4, 5, 6, 7, 8, 9, or 10. In prepolymers of Formula (1), each r can independently be an integer from 2 to 4, from 2 to 6, or from 2 to 8.

[0117] Examples of suitable dithiols include 1,2-ethanedithiol, 1,2-propanedithiol, 1,3- propanedithiol, 1,3-butanedithiol, 1,4-butanedithiol, 2,3-butanedithiol, 1,3-pentanedithiol, 1,5- pentanedithiol, 1,6-hexanedithiol, 1,3-dimercapto-3-methylbutane, dipentenedimercaptan,ethylcyclohexyldithiol (ECHDT), dimercaptodiethylsulfide, methyl-substituted dimercaptodiethylsulfide, dimethyl-substituted dimercaptodiethylsulfide, dimercaptodioxaoctane, 1,5-dimercapto-3-oxapentane, and a combination of any of the foregoing.

[0118] A dithiol may have one or more pendent groups comprising a lower (e.g., C1-6) alkyl group, a lower alkoxy group, or a hydroxyl group. Suitable alkyl pendent groups include, for example, C1-6linear alkyl, C3-6branched alkyl, cyclopentyl, and cyclohexyl.

[0119] Other examples of suitable dithiols include dimercaptodiethylsulfide (DMDS) (in Formula (3), R1is —[(CH2)p—X—]q(CH2)r—, wherein p is 2, r is 2, q is 1, and X is S); (3), R1is —[(CH2)p—X—]q(CH2)r—, wherein p is2, q is 2, r is 2, and X is O); and 1,5-dimercapto-3-oxapentane (in Formula (3), R1is —[(CH2)p— X—]q(CH2)r—, wherein p is 2, r is 2, q is 1, and X is O). It is also possible to use dithiols that include both heteroatoms in the carbon backbone and pendent alkyl groups, such as methyl groups. Such compounds include, for example, methyl-substituted DMDS, such as HS— CH2CH(CH3)—S—CH2CH2—SH, HS—CH(CH3)CH2—S—CH2CH2—SH and dimethyl substituted DMDS, such as HS—CH2CH(CH3)—S—CH(CH3)CH2—SH and HS— CH(CH3)CH2—S—CH2CH(CH3)—SH.

[0120] Suitable divinyl ethers for preparing thiol-terminated polythioethers include, for example, divinyl ethers of Formula (4): CH2═CH—O—(R2—O)m—CH═CH2(4)

[0121] where each R2independently comprises C1-10alkanediyl, C6-8cycloalkanediyl, C6-14 alkanecycloalkanediyl, or —[(CHR3)p—X—]q(CHR3)r—, where each R3can independently comprise hydrogen or methyl; each X can independently comprise O, S, or NR wherein R can comprise hydrogen or methyl; p can be an integer from 2 to 6; q can be an integer from 1 to 5; and r can be an integer from 2 to 10.

[0122] Suitable divinyl ethers include, for example, compounds having at least one oxyalkanediyl group —R2—O—, such as from 1 to 4 oxyalkanediyl groups, i.e., compounds in which m in Formula (4) is an integer ranging from 1 to 4. The variable m in Formula (4) can be an integer ranging from 2 to 4. It is also possible to employ commercially available divinyl ether mixtures that are characterized by a non-integral average value for the number of oxyalkanediylunits per molecule. Thus, m in Formula (4) can also take on rational number values ranging from 0 to 10.0, such as from 1.0 to 10.0, from 1.0 to 4.0, or from 2.0 to 4.0.

[0123] Examples of suitable vinyl ethers include ethylene glycol divinyl ether (EG-DVE) (R2in Formula (4) is ethanediyl and m is 1), butanediol divinyl ether (BD-DVE) (R2in Formula (4) is butanediyl and m is 1), hexanediol divinyl ether (HD-DVE) (R2in Formula (4) is hexanediyl and m is 1), diethylene glycol divinyl ether (DEG-DVE) (R2in Formula (4) is ethanediyl and m is 2), triethylene glycol divinyl ether (R2in Formula (4) is ethanediyl and m is 3), tetraethylene glycol divinyl ether (R2in Formula (4) is ethanediyl and m is 4), cyclohexanedimethanol divinyl ether, polytetrahydrofuryl divinyl ether; trivinyl ether monomers, such as trimethylolpropane trivinyl ether; tetrafunctional ether monomers, such as pentaerythritol tetravinyl ether; and combinations of two or more such polyvinyl ether monomers. A polyvinyl ether may have one or more pendent groups which can comprise alkyl groups, hydroxyl groups, alkoxy groups, or amine groups.

[0124] Divinyl ethers in which R2in Formula (4) is C3-6branched alkanediyl may be prepared by reacting a polyhydroxyl compound with acetylene. Examples of divinyl ethers of this type include compounds in which R2in Formula (4) is an alkyl-substituted methanediyl group such as CH(—CH3), or an alkyl-substituted ethanediyl.

[0125] Two or more types of divinyl ethers of Formula (4) may be used. Thus, two dithiols of Formula (3) and one divinyl ethers of Formula (4), one dithiol of Formula (3) and two divinyl ethers of Formula (4), two dithiols of Formula (3) and two divinyl ethers of Formula (4), and more than two compounds of one or both Formula (3) and Formula (4), may be used to produce a variety of thiol-terminated polythioethers prepolymers.

[0126] The divinyl ether(s) can comprise, for example, from 20 mole percent to less than 50 mole percent of the reactants used to prepare a thiol-terminated polythioether prepolymer, or 30 mole percent to less than 50 mole percent.

[0127] Relative amounts of dithiols and divinyl ethers can be selected to yield polythioether prepolymers having terminal thiol groups. Thus, a dithiol of Formula (3) or a mixture of at least two different dithiols of Formula (3), can be reacted with of a divinyl ether of Formula (4) or a mixture of at least two different divinyl ethers of Formula (4) in relative amounts such that the molar ratio of thiol groups to alkenyl groups is greater than 1:1, such as from 1.1:1.0 to 2.0:1.0.

[0128] The reaction between dithiols and divinyl ethers and / or polythiols and polyvinyl ethers may be catalyzed by a free radical catalyst, an ionic catalyst, or ultraviolet radiation. Suitable free radical catalysts include, for example, azo compounds, for example azobisnitriles such as azo(bis)isobutyronitrile (AIBN); organic peroxides such as benzoyl peroxide and t-butyl peroxide; and inorganic peroxides such as hydrogen peroxide. In certain reactions, the catalyst does not comprise acidic or basic compounds, and does not produce acidic or basic compounds upon decomposition. Examples of suitable free-radical catalysts include azo-type catalysts, such as Vazo®-57 (Du Pont), Vaze-64 (Du Pont), Vaze-67 (Du Pont), V-70® (Wako Specialty Chemicals), and V-65B® (Wako Specialty Chemicals). Examples of other suitable free-radical catalysts include alkyl peroxides, such as t-butyl peroxide. The reaction may also be affected by irradiation with ultraviolet light either with or without a cationic photoinitiating moiety.

[0129] Thiol-terminated polythioether prepolymers provided by the present disclosure may be prepared by combining at least one dithiol of Formula (3) and at least one divinyl ether of Formula (4) followed by addition of an appropriate catalyst, and carrying out the reaction at a temperature, for example, within a range from 30°C to 120°C, such as 70°C to 90°C, for a duration, for example, within a range from 2 hours to 24 hours, such as 2 hours to 6 hours.

[0130] Thiol-terminated polythioethers may comprise a polyfunctional polythioethers, i.e., may have an average thiol functionality greater than 2.0. Suitable polyfunctional thiol- terminated polythioether include, for example, those having the structure of Formula (2b): {HS—R1—[S—(CH2)2—O—(R2—O)m—(CH2)2—S—R1—]nS—V′—}zB (2b)

[0131] wherein z has an average value of greater than 2.0, such as a value within a range from 2 and 3, a value within a range from 2 and 4, a value within a range from 3 and 6, or can be an integer from 3 to 6.

[0132] Polyfunctionalizing agents suitable for use in preparing such polyfunctional thiol- terminated include trifunctionalizing agents, that is, compounds where z is 3. Suitable trifunctionalizing agents include, for example, triallyl cyanurate (TAC), 1,2,3-propanetrithiol, isocyanurate-containing trithiols, and combinations thereof, as disclosed in U.S. Application Publication No. 2010 / 0010133, which is incorporated by reference in its entirety; and isocyanurates as disclosed, for example, in U.S. Application Publication No. 2011 / 0319559, which is incorporated by reference in its entirety. Other useful polyfunctionalizing agentsinclude trimethylolpropane trivinyl ether, and the polythiols described in U.S. Pat. Nos. 4,366,307; 4,609,762; and 5,225,472, each of which is incorporated by reference in its entirety. Mixtures of polyfunctionalizing agents may also be used. As a result, polythioethers provided by the present disclosure may have a wide range of average functionality. For example, trifunctionalizing agents may afford average functionalities of groups capable of reacting with thiol groups from 2.05 to 3.0, such as from 2.1 to 2.6. Wider ranges of average functionality may be achieved by using tetrafunctional or higher functionality polyfunctionalizing agents. Functionality may also be determined by factors such as stoichiometry, as will be understood by those skilled in the art.

[0133] Polythioethers provided by the present disclosure are liquid at room temperature and can have a glass transition temperature Tg, for example, less than −20°C, less than −30°C, or less than −40°C. The glass transition temperature Tg can be determined by Dynamic Mass Analysis (DMA) using a TA Instruments Q800 apparatus with a frequency of 1 Hz, an amplitude of 20 microns, and a temperature ramp of −80°C to 25°C, with the Tgidentified as the peak of the tan δ curve.

[0134] The polythioethers can exhibit a viscosity, for example from 20 poise to 500 poise (2 Pa-sec to 50 Ps-sec), from 20 poise to 200 poise (2 Pa-sec to 20 Pa-sec) or from 40 poise to 120 poise 4 Pa-sec to 12 Pa-sec), measured using a Brookfield CAP 2000 viscometer, with a No. 6 spindle, at speed of 300 rpm, and a temperature of 25°C.

[0135] Polythioethers provided by the present disclosure can be characterized by a number average molecular weight and / or a molecular weight distribution. Polythioethers can exhibit a number average molecular weight, for example, from 500 Daltons to 20,000 Daltons, from 2,000 Daltons to 5,000 Daltons, or from 1,000 Daltons to 4,000 Daltons. Polythioethers can exhibit a polydispersity (Mw / Mn; weight average molecular weight / number average molecular weight), for example, from 1 to 20, or from 1 to 5. The backbone of a polythioether provided by the present disclosure can be modified to improve the properties such as adhesion, tensile strength, elongation, UV resistance, hardness, and / or flexibility of sealants and coatings prepared using polythioether prepolymers. For example, adhesion promoting groups, antioxidants, metal ligands, and / or urethane linkages can be incorporated into the backbone of a polythioether prepolymer to improve one or more performance attributes. Examples of backbone-modified polythioethers are disclosed, for example, in U.S. Pat. No. 8,138,273(urethane containing), U.S. Application Publication No. 2015 / 0240122 (sulfone-containing), U.S. Pat. No. 8,952,124 (bis(sulfonyl)alkanol-containing), U.S. Application Publication No. 2015 / 0240140 (metal-ligand containing), and U.S. Application Ser. No. 14 / 922,280 (antioxidant- containing) filed on Oct. 26, 2015, each of which is incorporated by reference in its entirety.

[0136] In addition to the thiol-terminated polythioethers of Formula (2a) and Formula (2b) other thiol-functional polythioethers and / or thiol-terminated sulfur-containing materials may also be used in compositions provided by the present disclosure, either independently or in combination with the polythioether prepolymers of Formula (2a) and Formula (2b). Examples of suitable thiol-functional polythioethers include thiol-terminated sulfur-containing polyformals and thiol-terminated polysulfidess.

[0137] An additional sulfur-containing can comprise a polythioether, a polysulfide, a sulfur-containing polyformal, or a combination of any of the foregoing. A sulfur-containing compound can comprise a polythioether or a sulfur-containing compound such as a polysulfide. A sulfur-containing compound may comprise a mixture of different polythioethers and / or polysulfides, and the polythioethers and / or polysulfides may have the same or different functionality. A sulfur-containing compound can have an average functionality from 2 to 6, from 2 to 4, from 2 to 3, from 2.3 to 2.8, or from 2.05 to 2.5. For example, a sulfur-containing compound can comprise a difunctional sulfur-containing compound, a trifunctional sulfur- containing compound, and a combination thereof. A sulfur-containing prepolymer can comprise a sulfur-containing polyformal.

[0138] A sulfur-containing compound can be thiol-terminated. Examples of thiol- terminated polythioether compounds s are disclosed, for example, in U.S. Pat. No. 6,172,179. A thiol-terminated polythioether compound can comprise Permapol® P3.1E, Permapol® L56086, or a combination thereof, each of which is available from PRC-DeSoto International Inc.

[0139] A thiol-terminated sulfur-containing compound can comprise a thiol-terminated sulfur-containing polyformal. Sulfur-containing polyformal compound useful in aerospace sealant applications are disclosed, for example, in U.S. Application Publication No. 2012 / 0234205 and in U.S. Application Publication No. 2012 / 0238707, each of which is incorporated by reference in its entirety.

[0140] A thiol-terminated sulfur-containing compound can comprise a thiol-terminated polysulfide. As used herein, the term polysulfide refers to a prepolymer that contains one ormore polysulfide linkages, i.e., —Sx— linkages, where x is from 2 to 4, in the backbone and / or in pendant positions on the prepolymer chain. A polysulfide compound can have two or more sulfur-sulfur linkages. Suitable polysulfides are commercially available, for example, from AkzoNobel and Toray Fine Chemicals under the names Thiokol-LP® and Thioplast®. Thioplast® products are available in a wide range of molecular weights ranging, for example, from less than 1,100 Daltons to over 8,000 Daltons, with molecular weight being the number average molecular weight in grams per mole. In some cases, the polysulfide has a number average molecular weight of 1,000 Daltons to 4,000 Daltons. The crosslink density of these products also varies, depending on the amount of crosslinking agent used. The —SH content, i.e., thiol or mercaptan content, of these products can also vary. The mercaptan content and molecular weight of the polysulfide can affect the cure speed of the prepolymer, with cure speed increasing with molecular weight.

[0141] Examples of suitable polysulfides are disclosed, for example, in U.S. Pat. Nos. 4,623,711; 6,172,179; 6,509,418; 7,009,032; and 7,879,955, each of which is incorporated by reference in its entirety.

[0142] A sulfur-containing compound can comprise a polysulfide selected from a Thiokol-LP® polysulfide, a Thioplast® polysulfide, and a combination thereof, such as Thioplast® G131, Thioplast® G21, and a combination thereof. Polyepoxides

[0143] Compositions disclosed herein can comprise a polyepoxide compound or a combination of polyepoxide compounds. A polyepoxide refers to a compound having two or more reactive epoxy groups. A polyepoxide can be difunctional or can include a combination of polyepoxides having different epoxy functionalities. A polyepoxide may include a combination of polyepoxides. A polyepoxide resin can be liquid at room temperature.

[0144] Examples of suitable polyepoxide compounds include hydantoin diepoxide, a diglycidyl ether of bisphenol -A, a diglycidyl ether of bisphenol-F, a novolac-type polyepoxide, epoxidized unsaturated phenolic resins, dimer acid-based epoxy resins, and combinations of any of the foregoing.

[0145] Other examples of suitable polyepoxides include a bisphenol A type polyepoxide, a brominated bisphenol A type polyepoxide, a bisphenol F type polyepoxide, a biphenyl type polyepoxide, a novolac type polyepoxide, an alicyclic polyepoxide, a naphthalene typepolyepoxide, an ether or polyether polyepoxide, an oxirane ring-containing polybutadiene, and a silicone polyepoxy copolymer.

[0146] Additional examples of suitable polyepoxides include a bisphenol A type polyepoxide having an average molecular weight, for example of 400 Daltons or less 600 Daltons or less, 1,000 Daltons or less, 1,200 Daltons or less, or 1 ,400 Daltons or less; a branched polyfunctional bisphenol A type polyepoxide such as p-glycidyloxyphenyl dimethyltolvlbisphenol A diglycidyl ether; a bisphenol F type epoxy resin; a phenol novolac type polyepoxide having an average molecular weight, for example, of 500 Daltons or less, 700 Daltons or less, 1,000 Daltons or less, or 1 ,500 Daltons or less; an alicyclic polyepoxide such as amyl(3,4-cyclohexene)dioxide, methyl 3,4-epoxycyclohexylcarboxylate (3,4- epoxycyclohexyl), bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate and 2-(3,4-epoxycyclohexyl)-5, 1 - spiro(3,4- epoxycyclohexyi)-m-dioxane; a biphenyl type polyepoxide such as 3,3',5,5'-tetramethyl-4,4'- diglycidyloxybiphenyl; a glycidyl ester type polyepoxide such as diglycidyl hexahydrophthalate, diglycidyl 3-methylhexahydrophthalate and diglycidyl hexa hydroterephthatate; a glycidylamine type polyepoxide such as diglycidylaniline, diglycidyltoluidine, triglycidyl-p-aminophenol, tetraglycidyl-m- xylene diamine, tetragiycidylbis(aminomethyl)cyclohexane; a hydantoin type polyepoxide such as 1,3- digiycidyl-5-methyl-5-ethylhydantoin; and a naphthalene ring- containing polyepoxide. Also, a polyepoxide having silicone such as l ,3~bis(3-gfycidoxy- propyl)~l ,l,3,3-tetramethyidisiioxane may be used.

[0147] Examples of commercially available polyepoxides suitable for use in the compositions disclosed herein include polyglycidyil derivatives of phenolic compounds, such as those available under the trade names EPON™ 824, EPON™ 825, EPON™ 826, EPON™ 82.7, EPO ™ 828, EPON™ 829, EPON™ 830, EPON™ 834, EPON™ 862, EPON™ 863, EPON™ 8280, EPON™ 8281, EPON™ 872 , an EPON™ resin blend, EPON™ 1001-A-80, EPON™ 1001-B-80, EPON™ lOOl-CX-75, EPON™ 1001-DNT-75, EPON™ 1001-FT-75, EPON™ 1001-G-70, EPON™ 1001-H-75, EPON™ 1001-K-65, EPON™ 1001-O-75, EPON™ 1001-T- 75, EPON™ 1001-UV-70, EPON™ 1001-X-75, EPON™ 1004-O-65, EPON™ 1007-CT-55, EPON™ 1007-FMU-50, EPON ™1007-HT-55, EPON™ 1009-DU-40, EPON™ 1009-MX-40, and other EPON™ epoxy resins, available, for example, from Momentive Specialty Chemicals Inc. and / or from Resolution Performance Products LLC; and DER™ 331, DER™ 332, DER™ 334, DER™ 354, DER™ 383 and DER™ 542 from Dow Chemical Co. Other suitablepolyepoxides include polyepoxides prepared from polyols and poly glycidyl derivatives of phenol-formaldehyde novolacs, the latter of which are commercially available under the trade names DEN™ 431, DEN'™ 438, and DEN'™ 439 from Dow Chemical Company. Cresol analogs are also available commercially ECN™ 1235, ECN™ 1273, and ECN™ 1299 from Ciba Specialty Chemicals, inc. SU-8 is a bisphenol A -type epoxy Novolac available from Resolution.

[0148] Performance Products LLC. Polyglycidyl adducts of amines, amino alcohols and polycarboxylic acids are also useful in the compositions disclosed herein, commercially available resins of which include GLY AMIN E™ 135, GLY AMINE™ 125, and GLY AMINE™ 115; ARALDITE™ MY-720, ARALDITE™ MY-721, ARALDITE™ 0500, and ARALDITE™ 0510 from Ciba Specialty Chemicals, Inc. and PGA-X and PGA-C.

[0149] A polyepoxide can include a combination of polyepoxides.

[0150] A polyepoxide can comprise a hydroxyl-functional polyepoxide or combination of hydroxyl - functional polyepoxides. For example, a polyepoxide can comprise a hydroxyl - functional diglycidyl ether of bisphenol A.

[0151] A diglycidyl ether of bisphenol A can comprise pendent hydroxyl groups such as, for example, from 1 to 10 pendent hydroxyl groups, from 1 to 8 hydroxyl groups, from 1 to 6 hydroxyl groups, from 1 to 4 pendent hydroxyl groups, or from 1 to 2 pendent hydroxyl groups, such as 1, 2, 3, 45, or 6 pendent hydroxyl groups. A diglycidyl ether of bisphenol A having pendent hydroxyl groups can be referred to as hydroxyl-functional diglycidyl ether of bisphenol A.

[0152] Hydroxyl-functional diglycidyl ethers of bisphenol A can have an epoxy equivalent weight from 400 Daltons to 1,500 Daltons, from 400 Daltons to 1,000 Daltons or from 400 Daltons to 600 Daltons.

[0153] A diglycidyl ether of bisphenol A can comprise a diglycidyl ether of bisphenol A without a hydroxyl-functional component, a diglycidyl ether of bisphenol A which can be partly hydroxyl-functional, or all of the diglycidyl ether of bisphenol A can be hydroxyl-functional.

[0154] A diglycidyl ether of bisphenol A having hydroxyl pendent groups can have the structure:

[0155] Examples of suitable diglycidyl ethers of bisphenol A include bisphenol A polyepoxides in which n is an integer 1 to 6, or a combination of bisphenol A polyepoxides in which n can be a non- integer value, for example, 0.1 to 2.9, 0.1 to 2.5, 0.1 to 2.1, 0.1 to 1.7, 0.1 to 1.5, 0.1 to 1.3, 0.1 to 1.1, 0.1 to 0.9, 0.3 to 0.8, or 0.5 to 0.8.

[0156] A diglycidyl ether of bisphenol A comprising hydroxyl pendent groups can comprise, for example, a 2,2-bis(p-glycidyloxyphenyl)propane condensation product with 2,2- bis(p- hydroxyphenyl)propane and similar isomers. Suitable diglycidyl ethers of bisphenol A comprising hydroxyl pendent groups are available, for example, from Momentive and include EPON™ solid epoxy resins such as EPON™ 100 IF, EPON™ 1002F, EPON™ 1004F, EPON™ 1007F, EPON™ 1009F, and combinations of any of the foregoing. Such diglycidyl ethers of bisphenol A may be provided, for example, as a 70 wt% to 95 wt% solids solution in a suitable solvent such as methyl ethyl ketone. Such high solids content resins include, for example, EPON™ 1001-A-80, EPON™ 1001-B-80, EPON™ lOOl-CX-75, EPON™ 1001-DNT-75, EPON™ 1001-FT-75, EPON™ 1001-G-70, EPON™ 1001-H-75, EPON™ 1001-K-65, EPON™ 1001-0-75, EPON™ 1001-T-75, EPON™ 1001-UY-70, EPON™ 1001- X-75, EPON™ 1004-O- 65, EPON™ 1007-CT-55, EPON™ 1007-FMU-50, EPON™ 1007-HT-55, EPON™ 1001-DU- 40, EPON™ 1009-MX-840, or a combination of any of the foregoing.

[0157] Examples of suitable epoxy novolac resins include novolac polyepoxides in which n is an integer 1 to 6, 1 to 4, or 1 to 2; or in which n can be a non-integer value, for example, 0.1 to 2.9, 0.1 to 2.5, 0.1 to 2.1, 0.1 to 1.7, 0.1 to 1.5, 0.1 to 1.3, 0.1 to 1.1, 0.1 to 0.9, 0.3 to 0.8, or from 0.5 to 0.8.

[0158] A polyepoxide can comprise, for example, a difunctional polyepoxide, a polyepoxide having an epoxy functionality greater than 2 such as 3 to 6, or a combination thereof. A polyepoxide can have an average epoxy functionality, for example, 2.1 to 3.5, 2.2 to 3.4, 2.6 to 3.2, or 2.7 to 3.1.

[0159] A polyepoxide can comprise, for example, a combination of a difunctional polyepoxide or combination of difunctional polyepoxides, a trifunctional polyepoxide or combination of trifunctional polyepoxides, or a combination of any of the foregoing.

[0160] A difunctional polyepoxide can have an epoxy equivalent weight, for example, from 400 Daltons to 1,500 Daltons, from 400 Daltons to 1,000 Daltons, or from 400 Daltons to 600 Daltons.

[0161] A trifunctional polyepoxide can have an epoxy equivalent weight, for example, from 140 Daltons to 500 Daltons, from 150 Daltons to 300 Daltons, or from 160 Daltons to 200 Daltons.

[0162] A difunctional polyepoxide can comprise, for example, a hydroxyl-functional polyepoxide and a trifunctional polyepoxide can comprise a hydroxyl-functional polyepoxide.

[0163] A composition can comprise, for example, a hydroxyl-functional polyepoxide and a trifunctional polyepoxide that does not contain pendent hydroxyl groups; or a composition can comprise a difunctional polyepoxide that does not contain pendent hydroxyl groups, and a hydroxyl-functional trifunctional polyepoxide.

[0164] A difunctional polyepoxide can comprise a hydroxyl-functional polyepoxide.

[0165] Compositions provided by the present disclosure can comprise a combination of polyepoxides. A combination of polyepoxides can comprise polyepoxides having different polyepoxides having different functionalities or different average functionalities. A combination of polyepoxides can comprise polyepoxides having an average epoxy functionality of at least 2. A combination of polyepoxides can comprise polyepoxides having an average epoxy functionality of no more than 3, such as no more than 2.9, such as no more than 2.8, such as no more than 2.7, such as no more than 2.5, such as no more than 2.3. A combination of polyepoxides can comprise polyepoxides having an average epoxy functionality of 2 to 3, such as 2 to 2.3, such as 2 to 2.5, such as 2 to 2.7, such as 2 to 2.8, such as 2 to 2.9. Accelerators

[0166] The coating composition may comprise an accelerator. Any accelerator capable of accelerating the curing of the multi-component composition may be used in the present disclosure. Examples of suitable accelerators are amine-based accelerators. Examples of amines that may be useful comprise quaternary amines, tertiary amines, cyclic tertiary amines, secondary amines, cyclic secondary amines, and primary amines. Some examples includetrimethylamine, butylamine, tributylamine, octylamine, laurylamine, dibutylamines, monoethanolamines, diethanolamines, triethanolamine, diethylenetriamine, triethylenetetriamine, oleylamines, diethanolamines, triethanolamine, cyclohexylamine, benzylamine, diethylaminopropylamine, xylylenediamine, triethylenediamine, guanidine, dimethylguanidine, tetramethylguanidine, pentamethylguanidine, phenylguanidine, diphenylguanidine, butylbiguanide, 1-o-tolylbiguanide, 1-phenylbiguanide, 1-methyl-3-nitroguanidine, 1,8- bis(tetramethylguanidino)-naphthalene, N,N,N’,N’-tetramethyl-N”-[4- morpholinyl(phenylimino)methyl]guanidine, 2,4,6-tris(dimethylaminomethyl)phenol, 2,2’- dimorpholinodiethylether, morpholine, N-methylmorpholine, 2-ethyl-4-methylimidazole, 1,8- diacabicyclo-(5,4,0)-undecene-7 (DBU), N,N-bis(N,N-dimethyl-2-aminoethyl)methylamine, N,N-dimethylcyclohexylamine, N-methylmorpholine, N-ethylmorpholine, piperidine; piperazine; pyrrolidine, homopiperazine, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1,4,5,6- tetrahydropyrimidine, 1,8-diazabicyclo[5.4.0]undec-7-ene; 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, 6- (dibutylamino)-1,8-diazabicyclo(5,4,0)undec-7-ene, 1,4-diazabicyclo[2.2.2]octane, 7- azabicyclo[2.2.1]heptane, N, N-dimethylphenylamine, 4,5-dihydro-1H-imidazole, or combinations thereof.

[0167] Examples of suitable commercial products that may be used include diethanolamine and triethanolamine T85 available from BASF; and Ancamine K-54, Curezol C17Z, DABCO 33-LV, Polycat DBU, and Vestamin IPD available from Evonik. Fillers

[0168] Coating compositions disclosed herein may comprise a filler.

[0169] Useful fillers include carbon black, calcium carbonate, precipitated calcium carbonate, calcium hydroxide, calcium silicates, aluminum powders, hydrated alumina (aluminum hydroxide), metal oxides, fumed silica (hydrophilic, hydrophobic, coated and / or uncoated), fused silica, silica, precipitated silica, and combinations of any of the foregoing. Suitable examples of filler include AEROSIL® fumed silicas from Evonik or HDK® from Wacker Chemie AG and / or Sipernat precipitated silicas from Evonik.

[0170] Useful fillers also include microspheres, polystyrene foam, microspheres of polyacrylates and polyolefins, and silica microspheres such as ECCOSPHERES® (Trelleborg Applied Technologies). Other examples include alumina / silica microspheres such as FILLITE®(Pluess-Stauffer International), aluminum silicate microspheres such as Z-LIGHT®, and calcium carbonate-coated polyvinylidene copolymer microspheres such as DUALITE 6001AE® (Pierce & Stevens Corp.). Other suitable fillers include, for example, hollow microspheres such as Expancel® microspheres (available from Nouryon) or Dualite® low density polymer microspheres (available from Henkel) or hollow borosilicate glass, such as 3M Glass bubbles type VS, K series and S series available from 3M. Compositions provided by the present disclosure include filler particles comprising an exterior surface coated with a thin coating, such as those described in U.S. Publication No. 2010 / 0041839 at paragraphs

[0016] -

[0052] , the cited portion of which is incorporated herein by reference.

[0171] Suitable fillers include, for example, those described in: U.S. Pat. No. 6,525,168, column 4, lines 14-55, incorporated herein by reference; and U.S. Pat. No. 8,816,023, column 3, line 18 to column 9, line 44, incorporated herein by reference.

[0172] The coating compositions may comprise a filler in an amount up to 60 percent by weight based on total weight of the coating composition, such as at least 20 percent by weight, such as at least 25 percent by weight. The coating compositions may comprise a filler in an amount of no more than 60 percent by weight based on total weight of the coating composition, such as no more than 50 percent by weight. The coating compositions may comprise the reinforcing filler in an amount of 20 percent by weight to 60 percent by weight based on total weight of the coating composition, such as 25 percent by weight to 50 percent by weight. Additives

[0173] Coating compositions provided by the present disclosure may further include one or more additives, including by way of non-limiting examples, adhesion promoters in addition to the thiol-functionalized catechol adduct, colorants, thixotropic agents, solvents, plasticizers, reactive diluents, pigments, masking agents, or a combination of any of the foregoing.

[0174] Suitable adhesion promoters include phenolics, such as Methylon® phenolic resin, and organosilanes, such as epoxy, mercapto, or amino functional silanes such as those described in U.S. Patent No. 11,066,584, column 18, line 61 to column 19, line 59, incorporated herein by reference. Useful examples of amino functional silanes include Silquest® A-187 and Silquest® A-1100. Other suitable adhesion promoters include alkyls, titanates and zirconates. Other useful adhesion promoters are known in the art.

[0175] If present at all, the coating compositions may comprise no more than 20 percent by weight of total additives based on total weight of the coating composition, such as no more than 10 percent by weight. If present at all, the coating compositions may comprise additives in a total amount of at least 0.1 percent by weight based on total weight of the coating composition, such as at least 0.2 percent by weight. If present at all, the coating compositions may comprise additives in a total amount of 0.1 percent by weight to 20 percent by weight based on total weight of the coating composition, such as 0.2 percent by weight to 10 percent by weight. Coating Compositions, Coatings and Systems

[0176] As described above, the coating compositions disclosed herein may be provided as multi-component coating compositions.

[0177] The coating compositions disclosed herein may be applied alone or as part of a coating system. Coating compositions disclosed herein may be applied directly onto the surface of a substrate or over an underlayer by any suitable coating process. Compositions can be deposited on substrates in a number of different ways, non-limiting examples of which include brushes, rollers, films, pellets, pressure injectors, spray guns and applicator guns. The system may comprise a number of the same or different layers and may further comprise other coating compositions such as pretreatment compositions, primers, and the like. A coating, film, layer or the like is typically formed when a composition that is deposited onto the substrate is cured by methods known to those of ordinary skill in the art (e.g., under ambient conditions and may further cure by through the use of an external energy source such as an oven or other thermal means or through the use of actinic radiation) to form a coating, layer or film. A multi- component composition may cure at ambient temperature. Compositions may be cured at a temperature of 0 to 40°C, such as 10°C to 25°C, and atmospheric humidity. A composition may be cured at a higher temperature such as at least 30°C, at least 40°C, or at least 50°C. When cured at room temperature a coating provided by the present disclosure can cure to a tack free surface, for example, within 24 hours, within 20 hours, within 16 hours, within 12 hours, within 6 hours, or within 3 hours, from the time of mixing. The skilled person understands, however, that the time of curing varies with temperature.

[0178] The coating compositions disclosed herein may comprise a a sealant composition or an adhesive composition.

[0179] The coating compositions may be cured to form a coating, such as a cured sealant or an adhesive. It was surprisingly discovered that the multi-component compositions disclosed herein, comprising one of the thiol-functionalized catechol adducts disclosed herein, form coatings, such as sealants or adhesives, that exhibit enhanced adhesion to a substrate surface, such as by exhibiting cohesive failure, while multi-component compositions that do not include one of the thiol-functionalized catechol adducts form coatings that do not exhibit enhanced adhesion to a substrate surface, such as by exhibiting adhesive failure.

[0180] Also disclosed herein are uses of the compositions disclosed herein for making a coating, wherein the coating exhibits enhanced adhesion to a substrate surface, such as by exhibiting cohesive failure.

[0181] Also disclosed herein are uses of a coating formed from the any of the compositions disclosed herein, to provide a substrate comprising a coating, wherein the coating exhibits enhanced adhesion to a substrate surface, such as by exhibiting cohesive failure. Substrates

[0182] Still further disclosed are substrates and articles comprising, or consisting essentially of, or consisting of, coatings formed from the compositions disclosed herein. For example, also disclosed is a coated substrate, wherein a portion of a surface of the substrate is partially coated with a coating formed from a composition disclosed herein. Also disclosed is an article comprising, or consisting essentially of, or consisting of, first and second substrates and a coating positioned there between and in a cured state.

[0183] The substrates that may be coated by the compositions of the present disclosure are not limited. Suitable substrates useful in the present disclosure include, but are not limited to, materials such as metals or metal alloys, ceramic materials such as boron carbide or silicon carbide, polymeric materials such as hard plastics including filled and unfilled thermoplastic materials or thermoset materials, or composite materials. Other suitable substrates useful in the present disclosure include, but are not limited to, glass or natural materials such as wood. For example, suitable substrates include rigid metal substrates such as ferrous metals, aluminum, aluminum alloys, magnesium titanium, copper, and other metal and alloy substrates. The ferrous metal substrates used in the practice of the present disclosure may include iron, steel, and alloys thereof. Non-limiting examples of useful steel materials include cold rolled steel, galvanized (zinc coated) steel, electrogalvanized steel, stainless steel, pickled steel, zinc-iron alloy such asGALVANNEAL, and combinations thereof. Combinations or composites of ferrous and non- ferrous metals can also be used. Aluminum alloys of the 1XXX, 2XXX, 3XXX, 4XXX, 5XXX, 6XXX, 7XXX, or 8XXX series as well as clad aluminum alloys and cast aluminum alloys of the A356, 1XX.X, 2XX.X, 3XX.X, 4XX.X, 5XX.X, 6XX.X, 7XX.X, or 8XX.X series also may be used as the substrate. Magnesium alloys of the AZ31B, AZ91C, AM60B, or EV31A series also may be used as the substrate. The substrate used in the present disclosure may also comprise titanium and / or titanium alloys of grades 1-36 including H grade variants. Other suitable non- ferrous metals include copper and magnesium, as well as alloys of these materials. The compositions disclosed herein are particularly suitable for use in various industrial or transportation applications including automotive, light and heavy commercial vehicles, marine, or aerospace. Suitable metal substrates for use in the present disclosure include those that are used in the assembly of vehicular bodies (e.g., without limitation, door, body panel, trunk deck lid, roof panel, hood, roof and / or stringers, rivets, landing gear components, and / or skins used on an aircraft), a vehicular frame, vehicular parts, motorcycles, wheels, and industrial structures and components. As used herein, “vehicle” or variations thereof includes, but is not limited to, civilian, commercial and military aircraft, and / or land vehicles such as cars, motorcycles, bicycles, including electric bicycles, and / or trucks. The metal substrate also may be in the form of, for example, a sheet of metal or a fabricated part. It will also be understood that the substrate may be converted, anodized, primed, organic-coated or chromate-coated, epoxy, urethane, graphite, fiberglass composite, Kevlar®, acrylics, and polycarbonates. The substrate may comprise a composite material such as a plastic or a fiberglass composite. The substrate may be a fiberglass and / or carbon fiber composite. The first and second substrates may be made of the same material or may be made of dissimilar materials. For example, a first substrate and a second substrate may be a metal and a plastic; two dissimilar plastics; a metal or a plastic and a reinforced plastic composite; or two dissimilar plastic composites.

[0184] In view of the foregoing description the present disclosure thus relates in particular to the following Aspects 1 to 41 without being limited thereto.

[0185] 1. A thiol-functionalized catechol adduct comprising: a catechol moiety incorporated into a backbone of a polythiol.

[0186] 2. The thiol-functionalized catechol adduct of aspect 1, comprising a thiol equivalent weight of at least 200 g / eq, such as at least 400 g / eq, such as no more than 800 g / eq, such as no more than 700 g / eq, such as 200 g / eq to 800 g / eq, such as 400 g / eq to 700 g / eq.

[0187] 3. The thiol-functionalized catechol adduct of aspect 1 or aspect 2, comprising Structure (I):formed from reactants comprising a substituted catechol and a polythiol.

[0189] 5. The thiol-functionalized catechol adduct of aspect 4, wherein the substituted catechol comprises a halogenated catechol.

[0190] 6. The thiol-functionalized catechol adduct of aspect 5, wherein the halogenated catechol comprises a monofunctional halogen and / or a difunctional halogen.

[0191] 7. The thiol-functionalized catechol adduct of any of aspects 4 to 6, wherein the substituted catechol comprises a theoretical molecular weight of at least 170 g / mol, such as at least 180 g / mol, such as no more than 720 g / mol, such as no more than 500 g / mol, such as 170 g / mol to 720 g / mol, such as 180 g / mol to 500 g / mol.

[0192] 8. The thiol-functionalized catechol adduct of any of aspects 4 to 7, wherein the substituted catechol comprises chloro-dihydroxyacetophenone, bromo- dihydroxyacetophenone or combinations thereof.

[0193] 9. The thiol-functionalized catechol adduct of any of aspects 4 to 8, wherein the polythiol comprises a theoretical thiol equivalent weight of at least 175 g / eq, such as at least 200 g / eq, such as no more than 550 g / eq, such as no more than 350 g / eq, such as 175 g / eq to 550 g / eq, such as 200 g / eq to 350 g / eq.

[0194] 10. The thiol-functionalized catechol adduct of any of aspects 4 to 9, wherein the polythiol comprises 1,8-dimercapto-3,6-dioxaoctane, dimercaptodiethylsulfide, or combinations thereof.

[0195] 11. The thiol-functionalized catechol adduct of any of aspects 4 to 10, comprising the polythiol and the substituted catechol in a molar ratio of at least 2:1, such as at least 3:1, such as no more than 6:1, such as no more than 5:1, such as 2:1 to 6:1, such as 3:1 to 5:1.

[0196] 12. The thiol-functionalized catechol adduct of any of the preceding aspects, wherein the adduct is formed according to Reaction Scheme (I):

[0197] 13. The thiol-functionalized catechol adduct of any of the preceding aspects formulated to enhance adhesion between a coating and a surface of a substrate.

[0198] 14. A coating composition comprising: the thiol-functionalized catechol of any of the preceding aspects; a polyepoxide; and an accelerator.

[0199] Aspect 15. A coating composition comprising: a first component comprising the thiol-functionalized catechol adduct of any of aspects 1 to 13; a second component comprising a polyepoxide; and an accelerator.

[0200] 16. The coating composition of aspect 14 or aspect 15, comprising:the thiol-functionalized catechol adduct in an amount of at least 1 percent by weight based on total weight of the coating composition, such as at least 2.5 percent by weight, such as no more than 20 percent by weight, such as no more than 15 percent by weight, such as 1 percent by weight to 20 percent by weight, such as 2.5 percent by weight to 15 percent by weight; the polyepoxide in an amount of at least 5 percent by weight based on total weight of the coating composition, such as at least 10 percent by weight, such as no more than 50 percent by weight, such as no more than 40 percent by weight, such as 5 percent by weight to 50 percent by weight, such as 10 percent by weight to 40 percent by weight; and / or the accelerator in an amount of at least 0.1 percent by weight, such as at least 0.2 percent by weight based on total weight of the coating composition, such as no more than 2 percent by weight, such as no more than 1.5 percent by weight, such as 0.1 percent by weight to 2 percent by weight, such as 0.2 percent by weight to 1.5 percent by weight.

[0201] 17. The coating composition of any of aspects 14 to 16, wherein the accelerator comprises triethylenediamine.

[0202] 18. The coating composition of any of aspects 14 to 17, the first component further comprising a polythiol prepolymer in addition to the thiol-functionalized catechol adduct.

[0203] 19. The coating composition of aspect 18, comprising the polythiol prepolymer in an amount of at least 40 percent by weight based on total weight of the coating composition, such as at least 45 percent by weight, such as no more than 80 percent by weight, such as no more than 75 percent by weight, such as 40 percent by weight to 80 percent by weight, such as 45 percent by weight to 75 percent by weight.

[0204] 20. The coating composition of aspect 18 or aspect 19, wherein the polythiol prepolymer comprises a thiol equivalent weight of at least 500 g / eq, such as at least 1000 g / eq, such as no more than 3000 g / eq, such as no more than 2500 g / eq, such as 500 g / eq to 3000 g / eq, such as 1000 g / eq to 2500 g / eq.

[0205] 21. The coating composition of any of aspects 18 to 20, wherein the polythiol comprises 1,8-dimercapto-3,6-dioxaoctane.

[0206] 22. The coating composition of any of aspects 18 to 21, comprising the thiol- functional catechol adduct and the polythiol prepolymer in a molar ratio of at least 0.5:1, such as at least 1:1, such as no more than 3:1, such as no more than 2.5:1, such as 0.5:1 to 3:1, such as 1:1 to 2.5:1.

[0207] 23. The coating composition of any of aspects 14 to 22, further comprising a filler and / or an additive.

[0208] 24. The coating composition of aspect 23, wherein the coating composition comprises the filler in an amount of at least 20 percent by weight based on total weight of the coating composition, such as at least 30 percent by weight, such as no more than 50 percent by weight, such as no more than 40 percent by weight, such as 20 percent by weight to 50 percent by weight, such as 30 percent by weight to 40 percent by weight.

[0209] 25. The coating composition of aspect 23 or aspect 24, wherein the additive comprises an adhesion promoter in addition to the thiol-functional catechol adduct.

[0210] 26. The coating composition of any of aspects 14 to 25, formulated as a sealant and / or an adhesive.

[0211] 27. A method of coating a substrate comprising applying the coating composition of any of aspects 14 to 26 to a portion of a surface of the substrate.

[0212] 28. A substrate comprising a coating on a surface thereof, the coating formed from the coating composition of any of aspects 14 to 26.

[0213] 29. The substrate of aspect 28, wherein the substrate comprises an article, a part, an assembly, or combinations thereof.

[0214] 30. The substrate of aspect 29, wherein the article comprises a vehicle, an appliance, a personal electronic device, a circuit board, a multi-metal substrate, or combinations thereof.

[0215] 31. The substrate of aspect 29, wherein the part comprises a vehicular part.

[0216] 32. The substrate of aspect 29, wherein the assembly comprises a vehicular part.

[0217] 33. The substrate of any of aspects 30 to 32, wherein the vehicle comprises a land vehicle or an aircraft.

[0218] 34. The substrate of aspect 33, wherein the land vehicle comprises an automobile or a bicycle such as an electronic bicycle.

[0219] 35. The substrate of any of aspects 28 to 34, wherein the substrate comprises aluminum or an alloy thereof.

[0220] 36. The substrate of aspect 35, wherein the alloy comprises copper.

[0221] 37. The substrate of any of aspects 28 to 36, wherein the coating comprises a sealant.

[0222] 38. The substrate of any of aspects 28 to 37, further comprising a second coating.

[0223] 39. The substrate of aspect 38, wherein the second coating comprises a primer.

[0224] 40. The substrate of any of aspects 28 to 39, wherein the coating provides cohesive failure.

[0225] 41. A use of the thiol-functionalized catechol adduct of any of aspects 1 to 13 to provide cohesive failure when formulated in a coating composition.

[0226] 42. A use of the coating composition of any of aspects 14 to 26 for making a coating that provides cohesive failure.

[0227] The following examples are intended to illustrate the disclosure and should not be construed as limiting the disclosure in any way. EXAMPLES Example 1: Synthesis Procedure of Thiol Derivative

[0228] A thiol-terminated adduct was synthesized by reacting 43.82 g of dimercaptodioxaoctane (DMDO) with 19.9 g triallyl cyanurate (TAC) at 77°C in the presence of VAZO-67 acting as the free radical catalyst for 16 hours. The chemical structure of the resulting thiol-terminated adduct is shown below:

[0229] 17.4 g of the Example 1 thiol and 156.6 g of tetrahydrofuran (THF) were added to a 500 ml 3-neck glass reactor equipped with a stirrer, a thermometer, and a nitrogen inlet. The content of the reactor was flushed with nitrogen under agitation.

[0230] 1.44 g KOH (85% aqueous solution) and 14.0 g methanol were added to an Erlenmeyer flask and stirred until a clear solution was formed, which was then added to the above thiol mixture in small portions through a plug of glass wool.

[0231] In a separate Erlenmeyer flask 4.05 g of chloro-dihydroxyacetophenone (CDHA) and 24.0 g methanol were added and stirred until a homogenous solution was formed. The solution was then added dropwise to the thiol solution through an addition funnel. Temperature of the solution at this stage was approximately 19.7°C. After addition of the CDHA was completed, the addition funnel was rinsed with 2 ml of methanol and added to the reactor content. The temperature of the solution increased to 20.7°C. Total addition time was 1 hour and 50 minutes.

[0232] The reactor content was stirred for another 9 hours at room temperature. The content of the reaction mixture was filtered first through a coarse sintered disc and then a fine one. The finished product had a theoretical structure as follows:

[0233] The sealant composition included (A) a thiol base composition and (B) an epoxy curing agent composition.

[0234] The thiol base composition was prepared using the ingredients set forth in Table 1. Table 1 Chemical Weight, gAccelerator 0.16 * The polythiol was synthesized per Example 1 of U.S. Patent No. 6,172,179

[0235] The epoxy curing agent composition was prepared using the ingredients set forth in Table 2 according to Example 1 of U.S. 2018 / 0194979. Table 2 Chemical Weight, g Adhesion Promoter* 5.7 uct

[0036] n ma ng a sea ant, 6.67 g o t e t iol base composition and 2.75 g of the epoxy curing agent composition were added to a Hauschild mixing cup. The content was mixed in a Hauschild mixer for 1 minute. The final mixture was homogeneous.

[0237] The mixture was used to make two sealant strips: one on clean bare aluminum and the second one on bare aluminum to which Scotchbrite® was applied and cleaned.

[0238] The sealant strips were cured first at room temperature for 7 days, then at 60°C for 2 days. The adhesion test was carried out qualitatively by cutting through the interface between the sealant strip and the substrate using a knife, while observing adhesion performance and failure. Cohesive failure was observed on both substrates. As used herein, “cohesive failure” means that the sealant strip demonstrated 100% adhesion. Example 4: Comparative Example

[0239] The sealant composition included two parts, the thiol base composition and the epoxy curing agent composition. The thiol base composition was prepared using the ingredients set forth in Table 3. Table 3 Chemical Weight, gent No. 6,172,179.

[0240] The epoxy curing agent composition was prepared as set forth in Example 3.

[0241] 16.67 g of the thiol base composition and 2.70 g of the epoxy curing agent composition were added to a Hauschild mixing cup. The content was mixed in a Hauschild mixer for 1 minute. The final mixture was homogeneous.

[0242] The mixture was used to make two sealant strips: one on clean bare aluminum and the second one on bare aluminum to which Scotchbrite® was applied and cleaned.

[0243] The sealant strips were cured first at room temperature for 7 days, then at 60°C for 2 days. The adhesion test was carried out qualitatively by cutting through the interface between the sealant strip and the substrate using a knife, while observing adhesion performance and failure. Adhesive failure was observed on both substrates. As used herein, “adhesive failure” means that the sealant strip did not demonstrate 100% adhesion.

[0244] Whereas particular features of the present disclosure have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the thiol-functionalized catechol adduct, coating composition, coating, and methods disclosed herein may be made without departing from the scope in the appended claims.

Claims

We claim:

1. A thiol-functionalized catechol adduct comprising: a catechol moiety incorporated into a backbone of a polythiol.

2. The thiol-functionalized catechol adduct of claim 1, wherein: (a) the thiol-functionalized catechol comprise a thiol equivalent weight of 200 g / eq to 800 g / eq; and / or (b) the catechol moiety comprises a theoretical molecular weight of 170 g / mol to 720 g / mol.

3. The thiol-functionalized catechol adduct of claim 1 or claim 2, comprising Structure (I):

4. The thiol-functionalized catechol adduct of any of the preceding claims, formed from reactants comprising a substituted catechol and a polythiol.

5. The thiol-functionalized catechol adduct of claim 4, wherein the substituted catechol comprises a halogenated catechol.

6. The thiol-functionalized catechol adduct of claim 4 or claim 5, wherein: (a) the polythiol comprises a theoretical thiol equivalent weight of 175 g / eq to 550 g / eq; and / or (b) the polythiol and the substituted catechol are in a molar ratio of 2:1 to 6:1.

7. The thiol-functionalized catechol adduct of any of the preceding claims, wherein the adduct is formed according to Reaction Scheme (I):

8. The thiol-functionalized catechol adduct of any of the preceding claims, formulated to enhance adhesion between a coating a surface of a substrate.

9. A coating composition comprising: the thiol-functionalized catechol of any of the preceding claims; a polyepoxide; and an accelerator.

10. A coating composition comprising: a first component comprising the thiol-functionalized catechol adduct of any of claims 1 to 8; a second component comprising a polyepoxide; and an accelerator.

11. The coating composition of claim 9 or claim 10, comprising:the thiol-functionalized catechol adduct in an amount of 1 percent by weight to 20 percent by weight; the polyepoxide in an amount of 5 percent by weight to 50 percent by weight; and / or the accelerator in an amount of 0.1 percent by weight to 2 percent by weight; wherein percent by weight is based on total weight of the coating composition.

12. The coating composition of any of claims 9 to 11, the first component further comprising a polythiol prepolymer in addition to the thiol-functionalized catechol adduct, a filler, and / or an additive.

13. The coating composition of any of claims 9 to 12, comprising the thiol-functional catechol adduct and the polythiol prepolymer in a molar ratio of 0.5:1 to 3:

1.

14. The coating composition of any of claims 9 to 13, formulated as a sealant and / or an adhesive.

15. A method of coating a substrate comprising applying the coating composition of any of claims 9 to 14 to a portion of a surface of the substrate.

16. A substrate comprising a coating on a surface thereof, the coating formed from the coating composition of any of claims 9 to 14.

17. The substrate of claim 16, wherein the substrate comprises an article, a part, an assembly, or combinations thereof.

18. The substrate of claim 17, wherein the article comprises a vehicle, an appliance, a personal electronic device, a circuit board, a multi-metal substrate, or combinations thereof.

19. The substrate of any of claims 16 to 18, wherein the vehicle comprises a land vehicle or an aircraft.

20. The substrate of any of claims 16 to 19, wherein the coating provides cohesive failure.

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