Synthesis of phthalonitrile resins

Abstract

Phthalonitrile resins and methods of forming phthalonitrile resins are described. The phthalonitrile resin is formed by reacting a primary amine-containing species and a phthalonitrile- containing species with an aldehyde to form a resin compound comprising at least one hexahydrotriazine node having a structure where each of R1, R2 and R3 is independently a backbone of the primary amine-containing species or a backbone of the phthal onitrile-containing species, and at least one of R1, R2 or R3 comprises the backbone of the phthalonitrile-containing species.

Description

Atorney Docket No. 950700-000002 PATENT1SYNTHESIS OF PHTHALONITRILE RESINSTECHNICAL FIELD

[0001] Embodiments of the disclosure are directed to methods for synthesizing phthalonitrile resins. In particular, embodiments of the disclosure are directed to methods for the melt state synthesis of phthalonitrile resins from precursor chemical species containing amine and phthalonitrile functional groups.BACKGROUND

[0002] Phthalonitriles are a unique and important class of polymeric materials which offer exceptional thermal and thermomechanical performance, critical criteria for applications in extreme environments. While the performance advantages of phthalonitriles have been well established by decades of published research, their usage has so far been hindered by the inefficiency of phthalonitrile synthesis by traditional solvothermal batch processes.

[0003] The solvothermal process includes combining a phenol with a nitro-functional phthalonitrile in a solution with a solvent (typically dimethylsulfoxide) in the presence of potassium carbonate. This mixture is allowed to react and is subsequently added to a large amount of water to precipitate the product, producing a large amount of hazardous chemical waste. The crude product is then washed several times with water to remove residual solvent and salts, further increasing the volume of chemical waste. Last, the product is dried under vacuum, a long and energy intensive process, before being packaged. Alternative solvothermal methods have also been developed, including the condensation of phosphochloride or acylchloride species with a phenoxide anion; however, these methods suffer the same drawbacks due to the presence of solvent, salts, and residual reagents in the crude reaction mixture which much be thoroughly removed to purify the monomer product. Additionally, the solvothermal process is expensive, slow, labor intensive, difficult to scale, and produces large amounts of hazardous chemical waste.

[0004] Accordingly, there is an ongoing need in the art for improved methods for producing phthalonitrile resins.Atorney Docket No. 950700-000002 PATENT2SUMMARY

[0005] In some embodiments, the techniques described herein relate to a method of forming a phthalonitrile resin, the method including: reacting a primary amine-containing species and a phthalonitrile-containing species with an aldehyde to form a resin compound including at least one hexahydrotriazine node having a structurewhere each of Rl, R2 and R3 is independently a backbone of the primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 includes the backbone of the phthalonitrile-containing species; applying a coating of the resin compound on an article; and curing the resin compound at temperatures ranging from 150 °C to 400 °C.

[0006] In some embodiments, the techniques described herein relate to a method of forming a composite material, the method including: forming a mixture including a primary amine- containing species, a phthalonitrile-containing species, and formaldehyde in a vessel; heating and stirring the mixture in the vessel under vacuum conditions to form a resin compound including at least one hexahydrotriazine node having a structurewhere each of Rl, R2 and R3 is independently a backbone of the primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 includesAtorney Docket No. 950700-000002 PATENT3 the backbone of the phthal onitrile-containing species; forming a resin article including injecting the resin compound into a mold, or coating an article with the resin compound.

[0007] In some embodiments, the techniques described herein relate to a method for generating a carbon-carbon composite, the method including: forming a phthalonitrile resin compound including a compound having at least one hexahydrotriazine node with a structurewhere each of Rl, R2 and R3 is independently a backbone of a primary amine-containing species or a backbone of a phthalonitrile-containing species, and at least one of Rl, R2 or R3 includes the backbone of the phthalonitrile-containing species; forming a mixture of the phthalonitrile resin and a reactive additive (RA); and pyrolyzing the mixture to generate the carbon-carbon composite.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0009] FIG. l is a flowchart of a method of forming a phthalonitrile resin according to one or more embodiments of the disclosure.

[0010] FIG. 2 is a schematic of an RTM reactor 150 according to one or more embodiments of the disclosure.Atorney Docket No. 950700-000002 PATENT4

[0011] FIG. 3 is a thermogravimetric analysis (TGA) plot of a phthalonitrile polymer according to one or more embodiments of the disclosure.DETAILED DESCRIPTION

[0012] Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways.

[0013] All patents, patent applications, published applications and publications, sequences, databases, websites and other published materials referred to throughout this disclosure are, unless noted otherwise, incorporated by reference herein in their entirety.

[0014] The term “about” as used herein means approximately or nearly and in the context of a numerical value or range set forth means a variation of ±15%, or less, of the numerical value. For example, a value differing by ±14%, ±10%, ±5%, ±2%, or ±1%, would satisfy the definition of about.

[0015] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the materials and methods discussed herein (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the materials and methods and does not pose a limitation on the scope unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods.Atorney Docket No. 950700-000002 PATENT5

[0016] The term monomer refers to a reactive thermosetting molecular structure of singular composition and with a 0 % degree of conversion or a thermoplastic monomer, while a “resin” refers to a reactive material which may potentially include some combination of different molecular structures, may potentially be polymerized to some degree, and may also include non- reactive components. Many of the synthetic procedures described by this invention have a natural tendency to produce some random but expected variety of different monomeric structures which may have undergone some degree of curing thereby constituting a resin.

[0017] Embodiments of the disclosure are directed to melt state synthesis of phthalonitrile resins from precursor chemical species containing amine and phthalonitrile functional groups which are reacted with formaldehyde through a condensation reaction. The resulting structure is comprised of 6-member heterocyclic aliphatic crosslinks herein referred to as nodes. This invention additionally describes the addition of other amine-functional species which are incorporated to modify the molecular structure of the resulting monomer. The monomers derived from this synthetic process undergo thermal crosslinking through the phthalonitrile functionality to form a cured phthalonitrile polymer network exhibiting high thermal and thermomechanical stability. As these reactions occur in a solvent free melt-state, this process may be performed as either a batch reaction process or a continuous reactive extrusion process. It is also possible to execute this process in the presence of solvent.

[0018] One or more embodiments of the disclosure advantageously provide synthetic methods which do not use solvents, salts, or residual reagents, thereby eliminating the need for purification and drying. Further, the chemical reactions described herein occur rapidly, thereby enabling synthesis by continuous reactive extrusion and dramatically increasing the potential scale of resin manufacturing.

[0019] Embodiments of the disclosure describe the combination of an amine-functional phthalonitrile precursor with formaldehyde in a melt state to yield a multi-functional phthalonitrile monomer through a condensation reaction forming one or more tri -functional nodes. Some embodiments of the disclosure describe the use of amine-functional structural modifiers to control the structure-processing-property relationship of the monomer or resin and the resulting cured network. The fundamental chemistry of this process is shown in Scheme (A), which displays theAtorney Docket No. 950700-000002 PATENT6 generic reaction between a primary amine (1) and formaldehyde (2) to form what is referred to herein as a node. Paraformaldehyde (PF A) may be used in place of formaldehyde to reduce health hazards.(1) (2) (3)

[0020] In some embodiments, a phthalonitrile resin is formed by reacting a primary amine- containing species and a phthalonitrile-containing species with an aldehyde to form a resin compound comprising at least one hexahydrotriazine node. As used herein, a “node” refers to a hexahydrotriazine having structure (3), where each of Rl, R2 and R3 is independently a backbone of a primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 comprises the backbone of the phthalonitrile-containing species.

[0021] As used in this manner, a “backbone” of a structure refers to the portions of the structure that are not modified during reaction to form the node. For example, a primary amine-containing species R-NFE (as shown in Scheme (A)) reacts to form the “node” and R- is the backbone of the species. As used herein, a “primary amine-containing species” refers to a compound with a primary amine group that will react to form the node. For example, the NEb group of the species R-NH2 is the primary amine and will result in formation of a CH2-N-CH2 portion of the node.Atorney Docket No. 950700-000002 PATENT7

[0022] As used herein, a “phthalonitrile-containing species” refers to a compound with an amine-functional group and a phthalonitrile group. A phthalonitrile group is shown in structure (4) where each R group is independently selected from hydrogen, a substituted or unsubstituted Cl- C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, or an alkoxy group, and at least one R group has a primary amine.

[0023] In some embodiments, the primary amine-containing species and the phthalonitrile- containing species are the same. For example, a species that has both a phthalonitrile group and a primary amine. In one or more embodiments, the phthalonitrile-containing species has the generic Structure (5), where A is a direct bond, an ether linkage, or a -C(CFa)2- linkage, and each R group is independently selected from hydrogen, a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group. Once the node has been formed, the backbone of the phthalonitrile-containing species and primary amine- containing species is shown in Structure (5B).Atorney Docket No. 950700-000002 PATENT

[0024] In some embodiments, a phthalonitrile resin compound is formed where R1 of the nodes is a phenyl group, and R2 and R3 of the nodes have the structurewhere A is a direct bond, an ether linkage, or a -C(CF3)2- linkage, and each R group is independently selected from hydrogen, a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group. As used in this specification, and the appended claims, substituted refers to the addition of one or more organic or halide side groups, ether linkages, carbonyl groups, hydroxyl groups, or other substituents known to the skilled artisan.

[0025] In some embodiments, the primary amine-containing species and the phthalonitrile- containing species include 4-(4-aminophenoxy)phthalonitrile (as shown in structure (6)), or a substituted 4-(4-aminophenoxy)phthalonitrile) where any of the implicit hydrogen atoms of Structure (6) is independently a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group.Atorney Docket No. 950700-000002 PATENT9

[0026] Some embodiments of the disclosure advantageously leverage the node forming reaction as a method of connecting amine-functional phthalonitrile-containing precursors to form multi-functional phthalonitrile monomers. Due to the modular nature of this synthetic method, any number of different amine-functional components, and combinations thereof, may be combined to form any number of different and unique molecular structures.

[0027] The following exemplary embodiments are a non-exhaustive list of different phthalonitrile resins / monomers which may be produced by embodiments of the disclosure, demonstrating the range of different design variations which may be leveraged to produce any number of different resin structures. These molecular design strategies extend to other material or monomer classes outside of phthalonitriles, including cyanate esters, acetylenes, epoxide, amine, bismaleimide, reactive / nonreactive diluents, etc. In some embodiments, the method includes a reaction between one or more of a primary amine-containing phthalonitrile, a primary amine- containing cyanate ester, a primary amine-containing acetylene, a primary amine-containing epoxide, a primary amine-containing amine, a primary amine-containing bismaleimide, a primary amine-containing reactive or nonreactive diluent.

[0028] Scheme (B) illustrates a reaction between a single amine- and phthalonitrile-containing species (structure (5)) and formaldehyde (Structure (2)) to form a single-amine single-node monomer structure (Structure (7)). Each R group is independently selected from hydrogen, a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, or an alkoxy group, and at least one R group has a primary amine.Atorney Docket No. 950700-000002 PATENT10

[0029] Scheme (C) illustrates a reaction between a single primary amine- and phthalonitrile- containing species (4-(4-aminophenoxy)phthalonitrile; structure (6)) and formaldehyde (structure (2)) to form a single-amine single-node monomer structure (Structure (8)). In some embodiments, any of the implicit hydrogen atoms of the primary amine- and phthalonitrile-containing species is independently a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group.(6) (2) (8)

[0030] The embodiment shown in Schemes (B) and (C) include three equivalents of a single primary amine- and phthalonitrile-containing precursor. The skilled artisan will recognize that three equivalents of the primary amine- and phthalonitrile-containing precursor can be replaced with a mixture of species with, for example, different R groups, so that there two or three differentAtorney Docket No. 950700-000002 PATENT11 species resulting in a single-node mixed monomer structure. In some embodiments, as shown in Schemes (B) and (C), one phthalonitrile compound including the primary amine-containing species and the phthalonitrile-containing species, may be reacted with an aldehyde to form a resin compound. The resultant resin compound has one node, where each of Rl, R2 and R3 (as shown in Structure (3)) comprises a backbone of the phthalonitrile compound.

[0031] Any amine-functional chemical species may be incorporated into the design of the nodeconnected resin structures. In cases of resins derived from multiple different amine-functional components, the resulting product is likely to contain a variety of different molecules connecting varying ratios of constituents. In such cases, the proposed structure is a theoretical ideal case wherein all product molecules consist of constituents expressing a ratio matching the ratio of precursor molecules reacted.

[0032] Scheme (D) illustrates an embodiment in which one equivalent of aminobenzene (Structure (9)) and two equivalents of 4-(4-aminophenoxy)phthalonitrile (Structure (6)) reacts with three equivalents of formaldehyde to form a multi-amine, single-node monomer structure (Structure (10)).(9) (6) (2) (10)

[0033] In some embodiments, the primary amine-containing species has more than one primary amine group, and the resultant resin compound has more than one node linked through the backbone of the primary amine-containing species. The incorporation of a multi-functional amine allows for an increase in the number of nodes which may be advantageous to achieve certain structure-property relationship effects. In these cases, the multifunctional amine acts as a linker, and varying the molar ratio of linkers and phthalonitrile end-caps can be leveraged to modify theAtorney Docket No. 950700-000002 PATENT12 molecular structure. These cases can be described by the ELN. As used herein, an “ELN” is the relative amounts of components where E, L and N denote the numbers of end-capping units, linkers, and nodes respectively. For example, Structure (7) has an ELN of 301, referring to three end-capping units (one benzene and two aminophenoxy phthalonitrile groups), zero linking units, and one node.

[0034] Scheme (E) represents an embodiment in which four equivalents of 4-(4- aminophenoxy)phthalonitrile (Structure (6)), one equivalent of 4,4’ -methylenedianiline (Structure (11)) and six equivalents of formaldehyde (Structure (2)) react to form Structure (12) which is a monomeric unit with four end caps, one linker and two nodes (ELN = 412).(6) (11) (2) (12)

[0035] Scheme F represents an embodiment in which five equivalents of 4-(4- aminophenoxy)phthalonitrile (Structure (6)), two equivalents of 4,4’-methylenedianiline (Structure (11)) and nine equivalents of formaldehyde (Structure (2)) react to form Structure (13) which is a monomeric unit with five end caps, two linkers, and three nodes (ELN= 523).(6) (11) (2) (13)Atorney Docket No. 950700-000002 PATENT13

[0036] The monomeric units described herein can be prepared by a combination of the constituent components in either a melt or solvent state. In the case of melt-state synthesis, either a batch or continuous process may be employed.

[0037] Melt-synthesis typically requires at least one of the components to melt or otherwise soften (become amorphous) allowing for other components to dissolve into the liquid mixture. Full dissolution of all components may not be necessary for effective manufacturing. The advantages of melt state synthesis include a faster rate of reaction, and the absence of solvent, and a substantial reduction or elimination of hazardous chemical waste production. Melt-state synthesis may also enable “B-staging” or partial polymerization of the resin to modify certain aspects of the processing and cure behavior, e.g., increasing the resin viscosity or shortening the cure time of composite fabrication.

[0038] One advantage to melt-state synthetic methods is the ability to execute chemical reactions by continuous reactive extrusion. By this method, solid or liquid precursor components are fed into an extruder which stirs (mixes) and heats the mixture while conveying it through the extrusion barrel. The extruder then expels the ready-to-use resin which can be cooled and packaged. To promote full conversion of the chemical reactants and to remove moisture from the product, the extruder may be equipped with a vacuum distillation port to extract the water byproduct. The design of the extruder feed screw is critical to controlling the shear mixing forces and the residency time in the heated barrel, while also allowing for the creation of low-pressure regions within the vacuum distillation zone to further aid in the removal of moisture. Another advantage of the continuous reactive extrusion method is the ability to mix a wide variety of different additives into the resin mixture in-situ while the reaction is taking place. The addition of additives such as viscosity modifiers, cure modifiers, co-curing resins, chopped fibers, nanoparticles, etc. during continuous reactive extrusion allow for synthesis and formulation to take place simultaneously in a single production step.

[0039] Some embodiments of the disclosure are directed to melt-state batch synthesis processes to form the monomeric units described herein. FIG. 1 is a flowchart of a method 100 of forming the monomeric units described herein as part of a resin transfer molding (RTM) process. FIG. 2 is a schematic of an RTM reactor 150 according to one or more embodiments of the disclosure.Atorney Docket No. 950700-000002 PATENT14Referring to FIGS. 1 and 2, the method 100 includes operation 102 in which all of the precursor chemicals (e.g., the primary amine-containing species, phthalonitrile-containing species and aldehyde) are mixed in a batch reactor vessel 155. At operation 104, the mixture 120 in the batch reactor vessel 155 is heated to melt and dissolve the precursors, and / or mixed using a suitable mechanical mixer 160.

[0040] At operation 106 of some embodiments of the method 100, the RTM reactor 150 is subjected to reduced pressure (i.e., vacuum) conditions using vacuum source 165 downstream of the batch reactor vessel 155. The vacuum source 165 can be used to remove moisture produced as a reaction byproduct from the headspace 125 of the batch reactor vessel 155 above the mixture 120 through a vacuum line 167. The vacuum source 165 can be any suitable vacuum source including, but not limited to, vacuum pumps (e.g., rotary vane pumps, turbo pumps, diffusion pumps) and forelines.

[0041] At operation 108 of some embodiments of method 100, the resin mixture 120, which has been synthesized, formulated, and de-gassed in the single batch reactor vessel 155, is pumped into a composite preform mold 180 through a heated injection line 175. The resin mixture 120 can be used as a coating and / or can be polymerized in a subsequent process. In some embodiments, the resin mixture 120 is polymerized and / or combusted to form carbon composites. In some embodiments, the resin compound is polymerized using the backbones of the phthalonitrile- containing species as cross-linking groups. In some embodiments, operation 108 includes coating an article with the composite material (resin compound).

[0042] In some embodiments, the method 100 is performed with use of a separate solvent to dissolve any of the precursors. The method 100 of some embodiments produces water as a reaction product. Water is not a solvent in the method 100 unless the water is specifically added as a separate component.

[0043] In some embodiments, the method 100 uses a separate solvent, which offers certain advantages in some circumstances. The reaction between an amine and formaldehyde may be carried out in the solvent in a batch reactor. As this method does not require any component to melt before the reaction can occur, the reaction may be carried out at a lower temperature. This may be necessary or otherwise advantageous when one or more of the precursor chemicals has aAtorney Docket No. 950700-000002 PATENT15 high melting point and / or a high melt-state viscosity. The temperature of the reaction will depend on the dissolution temperature of the precursor components in the chosen solvent, as well as the reactivity of the precursor components and the desired reaction rate. The solvent-state method may be enhanced through azeotropic distillation to remove water produced in-situ. Solvent-state synthesis may also be appropriate in cases where residual solvent in the final product may aid in processing. Solvent-state synthesis may also offer a higher degree of control over the reaction sideproducts.

[0044] One or more embodiments of the disclosure advantageously provide methods for producing monomers / resins in the melt state that eliminate the need to remove solvent and reagents from the final product, significantly simplifying, expediting, and reducing the cost and waste of manufacturing. Some embodiments of the method may be executed with chemicals that are already commercially available in large scale. In some embodiments, modularity of the synthetic process permits the synthesis of any number of different resins containing a wide range of different functionalities and structural properties, often without the need to significantly modify the process. In one or more embodiments, melt-state synthesis permits the blending of additives and other components into the mixture during the reaction, allowing for formulation and synthesis to occur simultaneously in a single step. Some embodiments advantageously offer significant reductions in the cost, speed, and complexity of manufacturing. Some embodiments of the described synthetic process offer substantial cost reductions over the current state or the art, specifically by reducing the cost of raw chemicals, process operation, labor, waste handling, and scaling.

[0045] Some embodiments of the disclosure provide methods for producing phthalonitrile-type monomers and resins. However, the use of the reaction between amines and formaldehyde to form branched monomeric molecular structures may be extended for use in any number of different end- group types, including both reactive and non-reactive end-groups, and combinations thereof. Precursors using alternative end-groups to phthalonitriles include a primary amine functional group. Variations of the end-group may be leveraged to control various aspects of the resulting resin or monomer and the cured materials made therefrom including structure-property relationships (e g., cured Tg, modulus, char yield, etc.), structure-processing relationships (e.g.,Atorney Docket No. 950700-000002 PATENT16 viscosity, melt / softening temperature, etc.), and cure properties (e.g., cure temperature, cure rate, exergonicity, etc ).

[0046] Suitable non-limiting examples of alternative end-groups include amine-functional polymers and non-reactive diluents. For example, amine-functional polymers (e.g., 5- aminononane, as shown in Structure (14)) and amine multi-functional polymers (e.g., 4-amino-7- (3-aminobenzyl)pentadecane) as shown in Structure (15). In each of Structures (14) and (15), any of the implicit hydrogen atoms can be replaced with independently a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group.(14) (15)

[0047] Some embodiments of the disclosure use precursors with amine-functional reactive precursors (e.g., cyanate esters, acetylenes, mal eimides, epoxides, etc.). Structure (16) is a nonlimiting example of a suitable cyanate ester. Structure (17) is a non-limiting example of a suitable acetylene, where R is selected from hydrogen, a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C 10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, or an alkoxy group. Structure (18) is a non-limiting example of a suitable maleimide. Structure (19) is a non-limiting example of a suitable epoxide. In some embodiments, side reactions between the epoxide and amine functional groups may occur. In each of Structures (16), (17), (18) and (19), any of the implicit hydrogen atoms can be replaced with independently a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group.Atorney Docket No. 950700-000002 PATENT17

[0048] Some embodiments of the disclosure use precursors with amine-functional heterogeneous structures (e.g., nanoparticles, substrates, etc.). Structure (20) is a non-limiting example of a suitable nanoparticle (e.g., a carbon nanotube).

[0049] The aldehyde reactant can be varied and may affect the reaction rates, stoichiometry and ratio of corresponding reaction products. For example, a larger aldehyde may react slower with some primary amine-containing species than with some phthalonitrile-containing species, which may affect the ELN of the subsequent resin monomer. In some embodiments, the aldehyde reactant increases the rate or thermodynamic driving force of the reaction of a multi-functional primary amine-containing species relative to the reaction with a phthalonitrile-containing species, increasing the likelihood of additional node formation relative to end cap formation. For example, referring back to Scheme F, the end nodes of the resultant Structure (13) include two phthalonitrile end caps. Some aldehydes may reduce the likelihood of two phthalonitriles forming the node with one linker, increasing the number of nodes in the resultant structure.

[0050] In some embodiments, the aldehyde includes a compound with the general formula R-C(=O)H, where R is selected from hydrogen, a Cl -CIO alkyl group, a Cl -CIO alkenyl group, a Cl -CIO alkynyl group, a C3-C10 cyclic group, or a halogen. In some embodiments, the aldehyde is formaldehyde. In some embodiments, the aldehyde reactant is selected from the group consistingAtorney Docket No. 950700-000002 PATENT18 of formaldehyde (methanal), acetaldehyde (ethanal), propanal, butanal, pentanal, hexanal, and furfural. In some embodiments, unreacted primary amines in the final product may be achieved by increasing the ratio of amine functional groups to the aldehyde (e.g., formaldehyde). The resulting product will likely contain a mixture of different structures which may not all exhibit primary amine functionality.

[0051] In some embodiments, the phthalonitrile resin is cured to form a polymeric network. The phthalonitrile resin of some embodiments is cured through different curing pathways. In some embodiments, curing the resin comprises a thermal reaction. The thermal reaction of some embodiments begins at a temperature ranging from about 155 °C to about 200 °C, and is gradually increased to temperatures as high as about 400 °C, 450 °C, or 500 °C. The polymeric network is formed by the phthalonitrile resin cures by reacting with itself to form the polymeric network.

[0052] Scheme (G) shows a reaction between a phthalonitrile and formaldehyde or paraformaldehyde to form the hexahydrotriazine monomer, followed by curing to form the polymer network.Atorney Docket No. 950700-000002 PATENT

[0053] The skilled artisan will recognize that the polymeric network formed in Scheme (G) is merely representative of one possible configuration. In some embodiments, the polymeric network includes a random assortment of different cross-linking structures.

[0054] A phthalonitrile polymer according to Structure (8) was prepared by mixing a 1 : 1 molar ratio of paraformaldehyde with 4-(4-aminophenoxy)phthalonitrile at 155 °C under vacuum conditions. The resulting resin was cast into a mold, heated to 175 °C and degassed to remove residual volatile species or air bubbles. The sample was cured in a step-wise manner by heating at a rate of 1 °C / min with isothermal holds at 175 °C (8 hours), 200 °C (2 hours), 250 °C (2 hours),Atorney Docket No. 950700-000002 PATENT20300 °C (2 hours), 325 °C (two hours), 350 °C (2 hours), and 375 °C (4 hours). FIG. 3 shows a thermogravimetric analysis (TGA) plot of a phthalonitrile polymer. The TGA plot demonstrates that the phthalonitrile resin has a high thermal stability that cannot be achieved with an uncured hexahydrotriazine structure alone. In some embodiments, the reaction products include combinations of resins and the inclusion of additives such as fdlers, reactive diluents, viscosity modifiers, char enhancers, heterogeneous particles (e.g., nanotubes, carbon black, inorganic powders, etc.), and reinforcing materials (e.g., chopped fibers). In some embodiments, the resin composite includes one or more of a reinforcing agent or a filler material.

[0055] Some embodiments of the disclosure are directed to phthalonitrile resins that can be melt processed, thermally cured to form a polymeric network, and pyrolyzed (e.g., 1000 °C) to form carbon-carbon composites with high carbon yields (>75%).

[0056] Some embodiments of the disclosure are directed to mixtures of phthalonitrile resins as described herein with a bis-ortho-diynyl-arene (BODA) compound having a Structure (21), where X is one or more of -C(CF3)2-, an ether linkage or a direct bond, and each R is independently selected from hydrogen, Cl -CIO alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, or a C4-C10 cyclic group.

[0057] The phthalonitrile resin acts as a reactive additive with the BODA, or vice versa, to form a reactive resin with improved carbon yield. In some embodiments, heating the composition including the BODA compound and the phthalonitrile resin to 1000 °C produces a reaction product including sp2hybridized turbostratic and graphitic carbon. In some embodiments, the reaction product has a carbon yield higher than an expected carbon yield based on a fractional average of individual component yields. In some embodiments, the carbon yield is greater than or equal to 10% higher on an absolute basis than the predicted or calculated carbon yield for the fractionalAtorney Docket No. 950700-000002 PATENT21 average of the components. In some embodiments, the carbon yield is increased by an amount greater than or equal to 15%, 20%, 25% or 30% absolute relative to the calculated carbon yield for the fractional average of the components.

[0058] In some embodiments, a carbon-carbon composite is prepared using a reaction product of the phthalonitrile resin with a reactive additive. Suitable reactive additives include, but are not limited to, products derived from, ketones (e.g., indanone), reactive resins (e.g., poly(indene), polybutadiene, polyisoprene, special ground tire rubber (GTR), polystyrene, xylilidenefluorene, xylilideneindene, truxene, isotruxene, and derivatives thereof), alkyne containing compounds (e.g., propargyl alcohol, propargyl amine, dipropargyl ethers, esters, tripropargylphosphine oxide, and derivatives thereof), and special reactive additives (e.g., acrylonitrile, triphenylphosphine, triphenylphosphine oxide, triphenylmethanol, and derivates thereof).

[0059] In some embodiments, the techniques described herein relate to a method of forming a phthalonitrile resin, the method including: reacting a primary amine-containing species and a phthalonitrile-containing species with an aldehyde to form a resin compound including at least one hexahydrotriazine node having a structurewhere each of Rl, R2 and R3 is independently a backbone of the primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 includes the backbone of the phthalonitrile-containing species; applying a coating of the resin compound on an article; and curing the resin compound at temperatures ranging from 150 °C to 400 °C.

[0060] In some embodiments, the techniques described herein relate to a method, wherein one phthalonitrile compound includes the primary amine-containing species and the phthalonitrile- containing species and the resin compound has one node where each of Rl, R2 and R3 include a backbone of the phthalonitrile compound.Atorney Docket No. 950700-000002 PATENT22

[0061] In some embodiments, the techniques described herein relate to a method, wherein the primary amine-containing species and the phthalonitrile-containing species are different compounds.

[0062] In some embodiments, the techniques described herein relate to a method, wherein and the resin compound has one node.

[0063] In some embodiments, the techniques described herein relate to a method, wherein the primary amine-containing species has more than one primary amine group, and the resin compound has more than one node linked through the backbone of the primary amine-containing species.

[0064] In some embodiments, the techniques described herein relate to a method, wherein the resin compound is polymerized using the backbones of the phthalonitrile-containing species as cross-linking groups.

[0065] In some embodiments, the techniques described herein relate to a method, wherein the aldehyde includes formaldehyde.

[0066] In some embodiments, the techniques described herein relate to a method, wherein the resin compound is formed by a melt-state synthesis process.

[0067] In some embodiments, the techniques described herein relate to a method of forming a composite material, the method including: forming a mixture including a primary amine- containing species, a phthalonitrile-containing species, and formaldehyde in a vessel; heating and stirring the mixture in the vessel under vacuum conditions to form a resin compound including at least one hexahydrotri azine node having a structureAtorney Docket No. 950700-000002 PATENT23 where each of Rl, R2 and R3 is independently a backbone of the primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 includes the backbone of the phthalonitrile-containing species; forming a resin article including injecting the resin compound into a mold, or coating an article with the resin compound.

[0068] In some embodiments, the techniques described herein relate to a method, wherein one phthalonitrile compound includes the primary amine-containing species and the phthalonitrile- containing species and the resin compound has one node where each of Rl, R2 and R3 include a backbone of the resin compound.

[0069] In some embodiments, the techniques described herein relate to a method, wherein the primary amine-containing species and the phthalonitrile-containing species are different compounds.

[0070] In some embodiments, the techniques described herein relate to a method, wherein the primary amine-containing species has more than one primary amine group, and the resin compound as more than one node linked through the backbone of the primary amine-containing species.

[0071] In some embodiments, the techniques described herein relate to a method, wherein the resin compound is polymerized using the backbones of the phthalonitrile-containing species as cross-linking groups.

[0072] In some embodiments, the techniques described herein relate to a method, wherein the mixture further includes one or more of a reinforcing agent or a filler material.

[0073] In some embodiments, the techniques described herein relate to a method, wherein the mixture further includes a bis-ortho-diynyl-arene (BOD A) compound having a formulaAtorney Docket No. 950700-000002 PATENT24 where X is one or more of -C(CF3)2-, an ether linkage or a direct bond, and each R is independently selected from a Cl -CIO alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, or a C4- C10 cyclic group.

[0074] In some embodiments, the techniques described herein relate to a method for generating a carbon-carbon composite, the method including: forming a phthalonitrile resin compound including a compound having at least one hexahydrotri azine node with a structurewhere each of Rl, R2 and R3 is independently a backbone of a primary amine-containing species or a backbone of a phthalonitrile-containing species, and at least one of Rl, R2 or R3 includes the backbone of the phthalonitrile-containing species; forming a mixture of the phthalonitrile resin and a reactive additive (RA); and pyrolyzing the mixture to generate the carbon-carbon composite.

[0075] In some embodiments, the techniques described herein relate to a method, wherein Rl is a phenyl group, R2 and R3 have the structurewhere A is a direct bond, an ether linkage, or a -C(CF3)2- linkage, and each R group is independently selected from hydrogen, a substituted or unsubstituted Cl -CIO alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group.Atorney Docket No. 950700-000002 PATENT25

[0076] In some embodiments, the techniques described herein relate to a method, wherein the reactive additive is a bis-ortho-diynyl-arene (BOD A) compound having a formulawhere X is one or more of -C(CF3)2-, an ether linkage or a direct bond, and each R is independently selected from a Cl -CIO alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, or a C4- C10 cyclic group.

[0077] In some embodiments, the techniques described herein relate to a method, further including heating the mixture to form a reaction product between the phthalonitrile resin and the BODA.

[0078] In some embodiments, the techniques described herein relate to a method, wherein a carbon yield of the mixture is greater than or equal to 10% higher on an absolute basis than the predicted or calculated carbon yield for the fractional average of the components.

[0079] Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0080] Although the disclosure herein has been described with reference to particular embodiments, those skilled in the art will understand that the embodiments described are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatusAtorney Docket No. 950700-000002 PATENT26 of the present disclosure without departing from the spirit and scope of the disclosure. Thus, the present disclosure can include modifications and variations that are within the scope of the appended claims and their equivalents.

Claims

Atorney Docket No. 950700-000002 PATENTWhat is claimed is:

1. A method of forming a phthalonitrile resin, the method comprising: reacting a primary amine-containing species and a phthal onitrile-containing species with an aldehyde to form a resin compound comprising at least one hexahydrotriazine node having a structurewhere each ofRl, R2 andR3 is independently a backbone of the primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 comprises the backbone of the phthalonitrile-containing species; applying a coating of the resin compound on an article; and curing the resin compound at temperatures ranging from 150 °C to 400 °C.

2. The method of claim 1, wherein one phthalonitrile compound includes the primary amine- containing species and the phthalonitrile-containing species and the resin compound has one node where each of Rl, R2 and R3 comprise a backbone of the phthalonitrile compound.

3. The method of claim 1, wherein the primary amine-containing species and the phthalonitrile-containing species are different compounds.

4. The method of claim 3, wherein and the resin compound has one node.

5. The method of claim 1, wherein the primary amine-containing species has more than one primary amine group, and the resin compound has more than one node linked through the backbone of the primary amine-containing species.Atorney Docket No. 950700-000002 PATENT286. The method of claim 1, wherein the resin compound is polymerized using the backbones of the phthalonitrile-containing species as cross-linking groups.

7. The method of claim 1, wherein the aldehyde comprises formaldehyde.

8. The method of claim 1, wherein the resin compound is formed by a melt-state synthesis process.

9. A method of forming a composite material, the method comprising: forming a mixture comprising a primary amine-containing species, a phthalonitrile- containing species, and formaldehyde in a vessel; heating and stirring the mixture in the vessel under vacuum conditions to form a resin compound comprising at least one hexahydrotriazine node having a structurewhere each of Rl, R2 and R3 is independently a backbone of the primary amine-containing species or a backbone of the phthalonitrile-containing species, and at least one of Rl, R2 or R3 comprises the backbone of the phthalonitrile-containing species; forming a resin article comprising injecting the resin compound into a mold, or coating an article with the resin compound.

10. The method of claim 9, wherein one phthalonitrile compound includes the primary amine- containing species and the phthalonitrile-containing species and the resin compound has one node where each of Rl, R2 and R3 comprise a backbone of the resin compound.Atorney Docket No. 950700-000002 PATENT2911. The method of claim 9, wherein the primary amine-containing species and the phthalonitrile-containing species are different compounds.

12. The method of claim 9, wherein the primary amine-containing species has more than one primary amine group, and the resin compound as more than one node linked through the backbone of the primary amine-containing species.

13. The method of claim 9, wherein the resin compound is polymerized using the backbones of the phthalonitrile-containing species as cross-linking groups.

14. The method of claim 9, wherein the mixture further comprises one or more of a reinforcing agent or a filler material.

15. The method of claim 9, wherein the mixture further comprises a bis-ortho-diynyl-arene(BOD A) compound having a formulawhere X is one or more of -C(CF3)2-, an ether linkage or a direct bond, and each R is independently selected from a Cl -CIO alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, or a C4-C10 cyclic group.

16. A method for generating a carbon-carbon composite, the method comprising: forming a phthalonitrile resin compound comprising a compound having at least one hexahydrotriazine node with a structureAtorney Docket No. 950700-000002 PATENT30where each of Rl, R2 and R3 is independently a backbone of a primary amine-containing species or a backbone of a phthal onitrile-containing species, and at least one of Rl, R2 or R3 comprises the backbone of the phthalonitrile-containing species; forming a mixture of the phthalonitrile resin and a reactive additive (RA); and pyrolyzing the mixture to generate the carbon-carbon composite.

17. The method of claim 16, wherein Rl is a phenyl group, R2 and R3 have the structurewhere A is a direct bond, an ether linkage, or a -C(CFa)2- linkage, and each R group is independently selected from hydrogen, a substituted or un substituted C1-C10 alkyl group, a substituted or unsubstituted C2-C 10 alkenyl group, a substituted or unsubstituted C2-C 10 alkynyl group, a substituted or unsubstituted C4-C10 cyclic group, a halogen, an alkoxy group, an amine group, a carboxylic acid group, an aldehyde group, a ketone group, or an alcohol group.Atorney Docket No. 950700-000002 PATENT3118. The method of claim 16, wherein the reactive additive is a bis-ortho-diynyl-arene (BODA) compound having a formulawhere X is one or more of -C(CF3)2-, an ether linkage or a direct bond, and each R is independently selected from a Ci-Cio alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, or a C4-C10 cyclic group.

19. The method of claim 18, further comprising heating the mixture to form a reaction product between the phthalonitrile resin and the BODA.

20. The method of claim 19, wherein a carbon yield of the mixture is greater than or equal to 10% higher on an absolute basis than a predicted or calculated carbon yield for a fractional average of components.

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