WO2018164709A1

WO2018164709A1 - Process for preparing polysilazanes

Info

Publication number: WO2018164709A1
Application number: PCT/US2017/047435
Authority: WO
Inventors: Stefan BOSSMAN; Hongwang Wang
Original assignee: Purple Solutions LLC
Current assignee: Purple Solutions LLC
Priority date: 2017-03-09
Filing date: 2017-08-17
Publication date: 2018-09-13
Anticipated expiration: 2019-09-09

Abstract

The present disclosure provides a method for preparing polysilazanes. The method comprises contacting one or more chlorosilanes with anhydrous liquid ammonia under ambient pressure at a temperature below about -33 °C. The amount of anhydrous liquid ammonia ranging between one and two times the stoichiometric amount of total silicon-chloride bonds in the chlorosilanes. The reaction mixture then warms to ambient temperature to evaporate the anhydrous liquid ammonia. The present disclosure further provides a method of using an ammonium scavenger to remove an ammonium salt from a polysilazane to provide a purified polysilazane.

Description

PROCESS FOR PREPARING POLYSILAZANES

TECHNICAL FIELD

[0001] The present disclosure generally relates to the synthesis of polysilazanes. More specifically, the present disclosure relates to the synthesis of polysilazanes from chlorosilanes and ammonia, and to the removal of ammonium salts from the reaction product.

BACKGROUND

[0002] Polysilazanes, which have a Si-N-Si bonding configuration, are increasingly important because they can be pyrolyzed to yield ceramic materials, such as silicon carbide and silicon nitride, and because they can be used in coating compositions which cure at room temperature under ambient conditions. To be effective, the polysilazanes should be substantially free of co-product contamination and of low molecular weight species.

[0003] Polysilazanes are usually synthesized by an ammonolysis process wherein ammonia or a primary amine reacts with a halide-substituted silane. Preparing silazane products by known ammonolysis methods, however, leads to unwanted co-products, such as ammonium chloride precipitates, which cause coating composition to be cloudy and which interfere with the pyro lysis reaction in ceramics manufacture. Increased additions of inert solvent to the reaction mixture are used to remove the ammonium chloride precipitates by decreasing the viscosity of the reaction mixture, improving agitation of the reaction mixture, and reducing the heat of reaction and/or heat of crystallization due to precipitating ammonium chloride. These benefits come at the cost of the ammonium chloride precipitates needing to be filtered out and the large volume of solvent needing to be removed from the final product.

[0004] Another problem encountered during the production of polysilazanes is the formation of a high proportion of low molecular weight species. These low molecular weight silazanes can evaporate during curing or pyrolysis, resulting in a reduced weight yield of the finished product relative to the stalling polysilazane material and resultant gaps in the finished coating or ceramic.

[0005] Accordingly, there is a need for a method of producing polysilazanes which removes unwanted co-products without excessive dilution and filtration. There is also a need for such methods to yield polvsilazanes which have a controlled proportion of low molecular weight species.

SUMMARY

[0006] The present disclosure provides methods for forming and purifying polysilazanes and their intermediates. The synthesis occurs in anhydrous liquid ammonia, which is then allowed to evaporate after the first stage of the reaction. Without wishing to be bound by theory, evaporating the ammonia increases the concentration of the other reagents in the reaction vessel, thereby promoting polymerization among the reaction intermediates and yielding polysilazanes with a controlled proportion of low molecular weight species. Although the synthesis reaction still produces ammonium salts by reaction of the chlorosilane starting material with the anhydrous liquid ammonia solvent, it has been discovered that ammonium scavengers can convert these ammonium salts to ammonia gas. The ammonia gas dissipates and the residual ammonium scavengers have surprisingly little impact on formulations using the polysilazanes.

[0007] Briefly, therefore, the present disclosure provides a method for preparing a compound comprising Formula (II). The method comprises (a) contacting one or more compounds comprising Formula (I) with anhydrous liquid ammonia under ambient pressure at a temperature below about -33 °C. A compound comprising Formula (II) and ammonium chloride are formed in this reaction. The amount of anhydrous liquid ammonia ranges between one and two times the stoichiometric amount of total silicon-chloride bonds in the one or more compounds comprising Formula (I), according to the following reaction scheme:

wherein:

R 1 and FT 2 are independently chosen from hydrogen, alkyl, alkenyl, and phenyl, wherein R 1 and R 2 may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides; and

n is greater than 2.

Controlling the stoichiometric ratio of ammonia to the compounds of Formula (I) promotes greater polymerization in the resulting product. The reaction mixture from step (a) is then allowed to attain ambient temperature to evaporate the anhydrous liquid ammonia. Step (a) may use anhydrous liquid ammonia as the only solvent.

[0008] Each R 1 and R 2 may be independently hydrogen, methyl, or vinyl. The number n may be greater than 2.5. R¹ may be hydrogen. In particular, the one or more compounds comprising Formula (I) may be selected from the group consisting of dichloro(methyl)silane, dichloro(methyl)(vinyl)silane, dichlorodimethylsilane, and combinations thereof. For example, the one or more compounds comprising Formula (I) may consist of a molar ratio ranging between about 10:90 to about 30:70 dichloro(methyl)silane to dichloro(methyl)(vinyl)silane, such as a molar ratio of about 20:80 dichloro(methyl)silane to dichloro(methyl)(vinyl)silane, or between about 60 wt.% and about80 wt.% dichlorodimethylsilane, and between about 40 wt.% and about 20 wt.% dichloro(methyl)silane. Specifically, the one or more compounds comprising Formula (I) may be dichloro(methyl)silane.

[0009] The method may further comprise contacting the compound of Formula (II) with a primary alkylamine NH₂R 3 , wherein R 3 is alkyl, in the presence of a solvent to form a mixture. The mixture is then heated to reflux for about 0.5 to 4 hours to produce a compound comprising Formula (III),

(III)

The solvent may be selected from the group consisting of aliphatic hydrocarbons, methyl acetate, isopropyl acetate, ieri-butyl acetate, such as an aliphatic hydrocarbon comprising n-heptane. The primary alkylamine may be methylamine.

[0010] The present disclosure also provides a method of using an ammonium scavenger to remove an ammonium salt from a polysilazane to provide a purified polysilazane. The method comprises (a) mixing a polysilazane containing an ammonium salt with a volume ratio of about 10: 1 to about 20: 1 solvent. The mixture of step (a) is contacted with an ammonium scavenger to convert the ammonium salt to ammonia, wherein the ammonium scavenger is a compound comprising Formula (IV),

wherein:

R⁴ is hydrogen or alkyleneamine;

L is alkylene; and

each R⁵ is independently selected alkyl.

The purified polysilazane is then separated.

[0011] R⁴ may be alkyleneamine. The alkyleneamine may be ethyleneamine. L may be propylene. R⁵ may be selected from the group consisting of methyl, ethyl, and propyl. In particular, the ammonium scavenger may be selected from the group consisting of 3- (aminopropyl)triethoxysilane, 3-(aminopropyl)methoxysilane, 3-(aminopropyl)tripropoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine). The weight ratio of the ammonium scavenger to the mixture of step (a) may range between about 1: 1 and about 20: 1, such as about 2.5: 1, or about 10: 1. The ammonium salt may be ammonium chloride. The polysilazane may be any compound comprising Formula (II), as defined herein.

[0012] The method may further comprise separating the ammonium salt from the mixture of step (a) before step (b), for example by filtering the mixture of step (a), by centrifuging the mixture of step (a), or by washing the mixture of step (a) with an about 1: 1 to about 20: 1 volume ratio of an aqueous proton acceptor to the mixture of step (a). When used, the aqueous proton acceptor may be selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, aqueous ammonia, and combinations thereof. The volume ratio of the aqueous proton acceptor to the mixture of step (a) may range between about 1:5 to about 1: 15, such as about 1: 10. The concentration of the aqueous proton acceptor may range between about 0.5 N to about 10 N, such as about 2 N. The method may further comprise using an ammonium scavenger to remove the ammonium salt from a polysilazane comprising the compound of Formula (II) to provide a purified polysilazane as disclosed herein.

[0013] The present disclosure further provides a method for preparing a polysilazane. The method comprises (a) contacting a mixture of Formula (I) selected from the group consisting of dichloro(methyl)silane, dichloro(methyl)silane/dichloro(methyl)(vinyl)silane,

dichloro(methyl)silane/ dichlorodimethylsilane, and dichloro(methyl)silane/ dichloro(methyl)(vinyl)silane/dichlorodimethylsilane, with a solvent consisting of anhydrous liquid ammonia under ambient pressure at a temperature below -33 °C. A polysilazane of Formula (II) and ammonium chloride are formed by the reaction. The amount of anhydrous liquid ammonia ranges between one and two times the stoichiometric amount of total silicon- chloride bonds in the mixture of Formula (I), according to the following reaction scheme:

R¹

I H

CI₂SiR¹R² - Si-N-r- + NH₄CI

R²

(I) (II)

wherein:

R 1 and FT 2 are hydrogen, methyl, or vinyl; and

n is greater than 2.

The reaction mixture from step (a) is then allowed to attain ambient temperature over the duration of between about 5 and about 7 hours to evaporate the anhydrous liquid ammonia.

[0014] The present disclosure further encompasses a composition, comprising a compound comprising Formula (II),

(II)

wherein:

R 1 and R 2" are independently chosen from hydrogen, alkyl, alkenyl, and phenyl, wherein

R 1 and R 2" may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides; and n is 2 or greater; and

an ammonium scavenger comprising Formula (IV),

wherein:

R >4 is hydrogen or alkyleneamine;

L is alkylene; and

each R⁵ is independently selected alkyl. [0015] The present disclosure also encompasses compositions comprising Formula (II),

(I I)

wherein:

R 1 and 2 are independently chosen from hydrogen, alkyl, alkenyl, and phenyl, wherein

R 1 and R 2" may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides; and

n is greater than 2; and

wherein the composition is substantially free of ammonium salts.

[0016] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification, or may be learned by the practice of the embodiments discussed herein. A further understanding of the nature and advantages of certain embodiments may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.

BRIEF DESCRIPTION OF THE FIGURES

[0017] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions.

[0018] Figure 1 depicts the Fourier transform infrared (FTIR) spectrum for

methylsilanediamine.

[0019] Figure 2 depicts the FTIR spectrum for methyl(vinyl)silanediamine.

[0020] Figure 3 depicts the FTIR spectrum for methylsilanediamine after reaction with liquid water/ammonia.

[0021] Figure 4 depicts the FTIR spectrum for a mixture of methy 1( vinyl) silanediamine and diamino(methyl)silanol after washing with water.

[0022] Figure 5 depicts the FTIR spectrum for a polysilazane (dichloro(methyl)silane (DMS):dichloro(methyl)(vinyl)silane (DVMS) 20:80 (mol/mol)) after three consecutive washings of the methyl acetate solution of the polysilazane with 10: 1 v/v 2N NaOH (aq). [0023] Figure 6 depicts the FTIR spectrum for a polysilazane (100% DMS).

[0024] Figure 7 depicts the FTIR spectrum for poly(methyl)silazane formed from the reaction of sodium amide and dichloro(methyl)silane.

DETAILED DESCRIPTION

[0025] The present disclosure provides a method for preparing polysilazanes, including compounds comprising Formula (II). The method comprises (a) contacting one or more compounds comprising Formula (I) with anhydrous liquid ammonia under ambient pressure at a temperature below about -33 °C. The reaction mixture from step (a) is then allowed to attain ambient temperature to evaporate the anhydrous liquid ammonia. The present disclosure also provides a method of using an ammonium scavenger to remove the ammonium salt from a polysilazane, such as a compound of Formula (II), to provide a purified polysilazane.

[0026] Polysilazanes usually do not vaporize due to the strong molecular interactions. Heat promotes crosslinking of the polysilazanes to form an even higher molecular weight structures. For example, at temperatures of 100-300 °C, hydrogen gas evolves and ammonia promotes further crosslinking. Once temperatures reach 700-1200 °C, the multi-dimensional amorphous network with Si, C and N atoms is formed, resulting in SiCN ceramic. "Pyrolysis" of polysilazanes produces ceramic materials with low viscosity in high yield, making polysilazanes an excellent choice for precursors for other ceramic matrices. As provided in the present disclosure, polymers combined with low molecular weight components offer added value for the generation of resistant and fast-curing coatings, because new chains can be formed that can improve and enhance the resulting material properties.

[0027] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification, or may be learned by the practice of the embodiments discussed herein. A further understanding of the nature and advantages of certain embodiments may be realized by reference to the remaining portions of the specification the drawings, the chemical structures, and descriptions, which forms a part of this disclosure. Any description of any R-group or chemical substituent, alone or in any combination, may be used in any chemical Formula described herein, and Formulae include all conformational and stereoisomers, including diastereomers, epimers, and enantiomers. Moreover any feature of a composition disclosed herein may be used in combination with any other feature of a composition disclosed herein. (I) Processes for the Preparation of a Compound Comprising Formula (II)

[0028] The present disclosure provides a method for preparing a compound comprising Formula (II). The method comprises (a) contacting one or more compounds comprising Formula (I) with anhydrous liquid ammonia under ambient pressure at a temperature below about -33 °C. A compound comprising Formula (II) and ammonium chloride are formed in this reaction. The amount of anhydrous liquid ammonia ranges between one and two times the stoichiometric amount of total silicon-chloride bonds in the one or more compounds comprising Formula (I). The method further comprises (b) allowing the reaction mixture from step (a) to attain ambient temperature to evaporate the anhydrous liquid ammonia. The method may further comprise using an ammonium scavenger to remove the ammonium salt from a polysilazane comprising the compound of Formula (II) to provide a purified polysilazane, as described below in Section (II).

(a) Step A of the process

[0029] Step A involves contacting one or more compounds comprising Formula (I) with anhydrous liquid ammonia under ambient pressure at a temperature below about -33 °C.

(i) Formula (I)

[0030] Compounds comprising Formula (I), Cl₂SiR 1 R 2 _, are disclosed herein.

Chlorosilanes (including SiC ) with more than two Si-Cl bonds may increase the networking in the resulting polysilazane. Chlorosilanes with less than two Si-Cl bonds would terminate polysilazane chains and decrease the degree of polymerization.

[0031] R 1 and R 2 may be independently chosen from hydrogen, alkyl, alkenyl, and phenyl. Each R 1 and R 2 may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides. Alternatively each R 1 and R 2 may be independently hydrogen, methyl, or vinyl. R 1 is hydrogen. In particular, R 1 and R2 may be hydrogen, methyl, or vinyl. Phenylated dichlorosilanes (wherein R 1 and/or R 2 is phenyl) when present may increase the temperature stability of the compounds of Formula (II) produced from the methods disclosed herein.

[0032] The one or more compounds comprising Formula (I) may be selected from the group consisting of dichloro(methyl)silane, dichloro(methyl)(vinyl)silane,

dichlorodimethylsilane, and combinations thereof. Certain mixtures of compounds of Formula (I) may be specified, such as those selected from the group consisting of dichloro(methyl)silane, dichloro(methyl)silane/ dichloro(methyl)(vinyl)silane, dichloro(methyl)silane/

dichlorodimethylsilane, and dichloro(methyl)silane/ dichloro(methyl)(vinyl)silane/

dichlorodimethylsilane. Specifically, the one or more compounds comprising Formula (I) may include dichloro(methyl)silane, singly or in combination with other compounds comprising Formula (I).

[0033] When mixtures are used, the molar ratio of the compounds comprising Formula (I) can and will vary. The one or more compounds comprising Formula (I) may consist of a molar ratio ranging between about 10:90 to about 30:70 dichloro(methyl)silane to

dichloro(methyl)(vinyl)silane. Alternatively, the one or more compounds comprising Formula (I) may consist of between about 60 wt.% and about 80 wt.% dichlorodimethylsilane, and between about 40 wt.% and about 20 wt.% dichloro(methyl)silane.

( ii) Formula (II)

[0034] As a result of Step A, a compound comprising Formula (II) and ammonium chloride are formed, as depicted in the reaction scheme below:

<■> (I D

[0035] R 1 and R 2 may be independently chosen from hydrogen, alkyl, alkenyl, and phenyl. Each R 1 and R 2 may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides. In particular, each R 1 and R 2 may be independently hydrogen, methyl, or vinyl. Alternatively, R¹ may be hydrogen.

[0036] The number n may range from about 2 to about 500, such as from about 10 to about 100, of from about 5 to about 10, from about 10 to about 25, from about 25 to about 50, from about 50 to about 75, from about 75 to about 100, from about 100 to about 200, from about 200 to about 300, from about 300 to about 400, or from about 400 to about 500. The number n may be less than about 500. The number n may be greater than 2. Alternatively, the number n may be greater than 2.5, such as greater than 4, greater than 5, greater than 6, greater than 7, greater than 8, greater than 9, greater than 10, greater than 15, greater than 20, greater than 25, greater than 30, greater than 35, greater than 40, greater than 45, or greater than 50. As used in this example, the term "about" refers to the average value for n in a given sample of compounds comprising Formula (II).

( Hi) solvent

[0037] The reaction mixture, as detailed herein, has a solvent comprising anhydrous ammonia. Step A may use anhydrous liquid ammonia as the only solvent, but the solvent may comprise additional non-aqueous solvents, depending on the compounds of Formula (I). Water causes unwanted decomposition of the polymerized material due to hydrolysis at the silicon atoms of the Si-N bonds. This reaction produces silanols, which continue react with other silicon centers until siloxanes are formed.

[0038] The additional solvent may be a polar protic solvent, a polar aprotic solvent, a non-polar solvent, or combinations thereof. Suitable examples of polar protic solvents include, but are not limited to alcohols such as methanol, ethanol, isopropanol, n-propanol, isobutanol, n- butanol, s-butanol, t-butanol, and the like; diols such as propylene glycol; organic acids such as formic acid, acetic acid, and so forth; amines such as trimethylamine, or triethylamine, and the like; amides such as formamide, acetamide, and so forth; and combinations of any of the above. Non-limiting examples of suitable polar aprotic solvents include acetonitrile, dichloromethane (DCM), diethoxymethane, N,N-dimethylacetamide (DMAC), Ν,Ν-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), Ν,Ν-dimethylpropionamide, l,3-dimethyl-3,4,5,6-tetrahydro- 2(lH)-pyrimidinone (DMPU), l,3-dimethyl-2-imidazolidinone (DMI), 1,2-dimethoxyethane (DME), dimethoxymethane, bis(2-methoxyethyl)ether, 1,4-dioxane, N-methyl-2-pyrrolidinone (NMP), ethyl formate, formamide, hexamethylphosphoramide, N-methylacetamide, N- methylformamide, methylene chloride, nitrobenzene, nitromethane, propionitrile, sulfolane, tetramethylurea, tetrahydrofuran (THF), 2-methyltetrahydrofuran, trichloromethane, and combinations thereof. Suitable examples of non-polar solvents include, but are not limited to, alkane and substituted alkane solvents (including cycloalkanes), aromatic hydrocarbons, esters, ethers, combinations thereof, and the like. Specific non-polar solvents that may be employed include, for example, benzene, butyl acetate, t-butyl methylether, chlorobenzene, chloroform, chloromethane, cyclohexane, dichloromethane, dichloroethane, diethyl ether, ethyl acetate, diethylene glycol, fluorobenzene, heptane, hexane, isopropyl acetate, methyltetrahydrofuran, pentyl acetate, n-propyl acetate, tetrahydrofuran, toluene, and combinations thereof. [0039] For example, the solvent, in addition to anhydrous liquid ammonia, may comprise an aliphatic solvent, such as n-heptane. Other suitable aliphatic hydrocarbons and mixtures thereof include aromatic hydrocarbons, such as benzene, toluene, and xylene. Alternatively, the solvent may also be chosen form methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, tert-butyl acetate, and mixtures thereof.

[0040] Since the anhydrous liquid ammonia is used as both a reagent and a solvent, it is present within the reaction mixture in a stoichiometric excess. However, the amount of anhydrous liquid ammonia may be restricted to between about 1 and about 2 times the stoichiometric amount of total silicon-chlorine bonds in the one or more compound comprising Formula (I).

[0041] In general, the volume ratio of the solvent to the compound comprising Formula (I) will range from about 0.5: 1 to about 100: 1. The volume ratio of the solvent to the compound comprising Formula (I) may range from about 0.5:1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the volume ratio of the solvent to the compound comprising Formula (I) may range from about 5: 1 to about 20: 1, such as between about 10: 1 and about 20: 1.

(iv) reaction conditions

[0042] In general, the reaction of Step A will be conducted at a temperature that ranges between about -200 °C and about -30 °C. The temperature of the reaction may range between about -200 °C and about -180 °C, between about -180 °C and about -160 °C, between about -160 °C and about -140 °C, between about -140 °C and about -120 °C, between about -120 °C and about -100 °C, between about -100 °C and about -80 °C, between about -80 °C and about -60 °C, or between about -60 °C and about -30 °C. The reaction may be conducted at temperature that ranges between about -60 °C and about -30 °C, from about -40 °C to about -30°C, or at about -33 °C. The temperature of the reaction may be below about -33 °C.

[0043] The reaction typically is performed under ambient pressure. The reaction may also be conducted under an inert atmosphere, for example under nitrogen, argon, or helium. Alternatively, the reaction may be conducted under an atmosphere of gaseous ammonia.

[0044] Generally, the reaction is allowed to proceed for a sufficient period of time until the reaction is complete, as determined by any method known to one skilled in the art, such as chromatography (e.g., HPLC). The duration of the reaction may range from about 5 minutes to about 10 hours. The duration of the reaction may range from about 5 minutes to about 30 minutes, from about 30 minutes to about 2 hours, from about 2 hours to about 4 hours, or from about 4 hours to about 10 hours. In particular, the reaction may be allowed to proceed for about 0.5 hour to about 2 hours. In this context, a "completed reaction" generally means that the reaction mixture contains a significantly diminished amount of the compound comprising Formula (I). Typically, the amount of the compound comprising Formula (I) remaining in the reaction mixture at the end of the reaction may be less than about 10%, less than about 5%, or less than about 2%.

[0045] The compound comprising Formula (II) may have a yield of at least about 60%. For example, the compound comprising Formula (II) may have a yield of at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99%.

(b) Step B of the process

[0046] Step B involves allowing the reaction mixture from Step A to attain ambient temperature to evaporate the anhydrous liquid ammonia. In allowing the temperature to rise, the reaction mixture need not be actively heated. Rather the reaction mixture can be left to equilibrate under ambient conditions until it is warm enough for the ammonia to evaporate.

[0047] The reaction of Step B may be conducted at a temperature that ranges from about -30 °C to about 100°C. The temperature of the reaction may range between about -30 °C and about -20 °C, between about -20 °C and about 0 °C, between about 0 °C and about 20 °C, between about 20 °C and about 40 °C, between about 40 °C and about 60 °C, between about 60 °C and about 80 °C, or between about 80 °C and about 100 °C. The reaction may be conducted at temperature that ranges between about 10 °C and about 40 °C, or between about 20 °C and about 30°C. Specifically, the temperature of the reaction may be about room temperature. The reaction generally will be conducted under inert atmosphere, for example under nitrogen, argon or helium.

[0048] Generally, the reaction is allowed to proceed for a sufficient period of time until the reaction is complete, as determined by any method known to one skilled in the art. The reaction may be allowed to proceed for a time that ranges from about 1 hour to about 30 hours. For example, the duration of the reaction may range from about 1 hour to about 4 hours, from about 4 hours to about 10 hours, from about 10 hours to about 18 hours, or from about 18 hours to about 30 hours. In particular, the reaction may be allowed to proceed between about 5 and about 7 hours to evaporate the anhydrous liquid ammonia.

(c) Step C of the process

[0049] The method may comprise a Step C, which involves contacting the compound of

Formula (II) with a primary alkylamine NH₂R 3 , wherein R 3 is alkyl, in the presence of a solvent to form a mixture; and heating the mixture to reflux for about 0.5 to 4 hours to produce a compound comprising Formula (III),

(III)

[0050] The compound of Formula (II) may be as defined herein.

(i) primary alkylamine

[0051] The primary alkylamine has a general formula of NH₂R 3 , wherein R 3 is alkyl. In particular, R 3 may be methyl, ethyl, propyl, or butyl. Especially, R 3 may be methyl. As such, the primary alkylamine may be methylamine, ethylamine, propylamine, or butylamine. Especially, the primary alkylamine may be methylamine.

( ii) Formula (III)

[0052] Disclosed herein are compounds comprising Formula (III),

(III)

R may be as defined above under the description of primary alkylamine.

[0053] R may be as defined above under the description of Formula (I), or any embodiments thereof.

[0054] The number n may be as defined above under the description of Formula (I), or any embodiments thereof. [0055] In general, the weight ratio of the primary alkylamine to the compound comprising Formula (II) will range from about 0.5:1 to about 100: 1. The weight ratio of the primary alkylamine to the compound comprising Formula (II) may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the weight ratio of the primary alkylamine to the compound comprising Formula (II) may range from about 5: 1 to about 20: 1, such as between about 10: 1 and about 20: 1.

( in) solvent

[0056] The solvent may be a polar protic solvent, a polar aprotic solvent, a non-polar solvent, or combinations thereof. Suitable examples of polar protic solvents include, but are not limited to alcohols such as methanol, ethanol, isopropanol, n-propanol, isobutanol, n-butanol, s- butanol, t-butanol, and the like; diols such as propylene glycol; organic acids such as formic acid, acetic acid, and so forth; amines such as trimethylamine, or triethylamine, and the like; amides such as formamide, acetamide, and so forth; and combinations of any of the above. Non-limiting examples of suitable polar aprotic solvents include acetonitrile, dichloro methane (DCM), diethoxymethane, Ν,Ν-dimethylacetamide (DM AC), Ν,Ν-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), Ν,Ν-dimethylpropionamide, l,3-dimethyl-3,4,5,6-tetrahydro-2(lH)- pyrimidinone (DMPU), l,3-dimethyl-2-imidazolidinone (DMI), 1,2-dimethoxyethane (DME), dimethoxymethane, bis(2-methoxyethyl)ether, 1,4-dioxane, N-methyl-2-pyrrolidinone (NMP), ethyl formate, formamide, hexamethylphosphoramide, N-methylacetamide, N-methylformamide, methylene chloride, nitrobenzene, nitromethane, propionitrile, sulfolane, tetramethylurea, tetrahydrofuran (THF), 2-methyltetrahydrofuran, trichloromethane, and combinations thereof. Suitable examples of non-polar solvents include, but are not limited to, alkane and substituted alkane solvents (including cycloalkanes), aromatic hydrocarbons, esters, ethers, combinations thereof, and the like. Specific non-polar solvents that may be employed include, for example, benzene, butyl acetate, t-butyl methylether, chlorobenzene, chloroform, chloromethane, cyclohexane, dichloromethane, dichloroethane, diethyl ether, ethyl acetate, diethylene glycol, fluorobenzene, heptane, hexane, isopropyl acetate, methyltetrahydrofuran, pentyl acetate, n- propyl acetate, tetrahydrofuran, toluene, and combinations thereof.

[0057] In particular, the solvent may be selected from the group consisting of aliphatic hydrocarbons, methyl acetate, isopropyl acetate, ieri-butyl acetate. Alternatively, the solvent may be an aliphatic hydrocarbon comprising n-heptane. [0058] In general, the volume ratio of the solvent to the compound comprising Formula (II) will range from about 0.5: 1 to about 100: 1. The volume ratio of the solvent to the compound comprising Formula (II) may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the volume ratio of the solvent to the compound comprising Formula (II) may range from about 5: 1 to about 20: 1, such as between about 10: 1 and about 20: 1.

(iv) reaction conditions

[0059] The reaction of Step C may be conducted at a temperature that allows the solvent to reflux. Reflux depends on the solvent, pressure of the reaction, and the concentration of reagents, among other factors. In general, the temperature may range from about 30 °C to about 200°C. The temperature of the reaction may range between about 30 °C and about 40 °C, between about 40 °C and about 50 °C, between about 50 °C and about 60 °C, between about 60 °C and about 70 °C, between about 70 °C and about 80 °C, between about 80 °C and about 90 °C, between about 90 °C and about 100 °C, between about 100 °C and about 110 °C, between about 110 °C and about 120 °C, between about 120 °C and about 130 °C, between about 130 °C and about 140 °C, between about 140 °C and about 150 °C, between about 150 °C and about 160 °C, between about 160 °C and about 170 °C, between about 170 °C and about 180 °C, between about 180 °C and about 190 °C, or between about 190 °C and about 200 °C. The reaction generally will be conducted under inert atmosphere, for example under nitrogen, argon or helium.

[0060] Generally, the reaction is allowed to proceed for a sufficient period of time until the reaction is complete, as determined by any method known to one skilled in the art. The reaction may be allowed to proceed for a time that ranges from about 10 minutes to about 8 hours. For example, the duration of the reaction may range from about 10 minutes to about 30 minutes, from about 30 minutes to about 1 hour, from about 1 hour to about 2 hours, from about 2 hours to about 3 hours, from about 3 hours to about 4 hours, from about 4 hours to about 5 hours, from about 5 hours to about 6 hours, from about 6 hours to about 7 hours, or from about 7 hours to about 8 hours. In particular, the duration of the reaction may range from about 30 minutes to about 4 hours.

[0061] The compound comprising Formula (III) may have a yield of at least about 60%. For example, the compound comprising Formula (III) may have a yield of at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99%.

(II) Processes for Removing Ammonium Salt from a Polysilazane

[0062] The present disclosure provides a method for using an ammonium scavenger to remove an ammonium salt from a polysilazane to provide a purified polysilazane. The method comprises mixing a polysilazane containing an ammonium salt with a volume ratio of about 10: 1 to about 20: 1 solvent, and contacting the mixture of Step A with an ammonium scavenger to convert the ammonium salt to ammonia.

(a) Step A of the process

[0063] Step A of the method involves mixing a polysilazane containing an ammonium salt with a volume ratio of about 10: 1 to about 20:1 solvent.

(i) Polysilazane

[0064] "Silazane" and "polysilazane" are generic terms which include compounds containing one or more silicon-nitrogen bonds in which the nitrogen atom is bonded to at least two silicon atoms, and may or may not contain cyclic units. Therefore, the terms "polysilazane" and "silazane polymer" include oligomers, cyclic, polycyclic, linear polymers or resinous polymers having at least one Si-N group in the compound, or having repeating units of H₂Si- NH; that is, [H₂Si-NH]_n, with "n" greater than 1. The chemical structure for an inorganic polysilazane is shown below.

H H H H

i 1 1 1

— i Sh- ¾ Si—

i f

H H

[0065] An example of silazane oligomer is disilazane H₃Si-NH-SiH₃.The oligomeric or polymeric silazanes may be amorphous or crystalline in nature. Silazane polymer chains having both large chains and small rings with a wide range of molecular mass are called poly silazanes. Polysilazanes or a mixture of polysilazanes known in the art or commercially available include such products generally known among persons skilled in the art as silazanes, disilazanes, polysilazanes, ureasilazanes, polyureasilazanes, aminosilanes, organosilazanes,

organopolysilazanes, inorganic polysilazanes, and others employing liquid anhydrous ammonia in their production. A polysilazane with the general formula (CH₃)₃Si-NH-[(CH₃)₂Si-NH]_n- Si(CH₃)3 is designated as polydimethylsilazane. One group of polysilazane, [RiR₂Si-NH]_n, is isoelectronic with and close relatives to polysiloxane [RiR₂Si-0]_n. Additionally, Si-N bond can be found in triethylsilylamine ((H₅C₂)₃Si-NH₂), which is a typical aminosilane. Further, small ring-shaped molecules with a base group of Si-N are called "cyclosilazanes." For example, triazatrisilane (H₉N₃S1₃) is a typical cyclotrisilazane.

[0066] In particular, the polysilane may be a compound comprising Formula (II), as disclosed herein.

(ii) solvent

[0067] The solvent may be as defined above under the description of Section (I)(c). In particular, the solvent may be selected from the group consisting of aliphatic hydrocarbons, methyl acetate, isopropyl acetate, and ieri-butyl acetate. For example, the solvent may be an aliphatic hydrocarbon comprising n-heptane.

[0068] In general, the volume ratio of the solvent to the polysilazane will range from about 0.5: 1 to about 100: 1. The volume ratio of the solvent to the polysilazane may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the volume ratio of the solvent to the polysilazane may range from about 5: 1 to about 20: 1, such as between about 10:1 and about 20: 1.

(b) Step B of the process

[0069] Step B involves contacting the mixture of Step A with an ammonium scavenger to convert the ammonium salt to ammonia.

(i) ammonium scavenger

[0070] Specifically, the ammonium scavenger may a compound comprising Formula

(IV),

wherein:

R⁴ is hydrogen or alkyleneamine; L is alkylene; and

each R⁵ is independently selected alkyl;

[0071] R⁴ may be alkyleneamine, such as methyleneamine, ethyleneamine,

propyleneamine, or butyleneamine. Specifically, the alkyleneamine may be ethyleneamine. L may be propylene. R⁵ may be selected from the group consisting of methyl, ethyl, and propyl. In particular, the ammonium scavenger may be selected from the group consisting of 3- (aminopropyl)triethoxysilane, 3-(aminopropyl)methoxysilane, 3-(aminopropyl)tripropoxysilane, and N- [3 -(trimethoxy silyl)propyl] ethylenediamine) .

[0072] In general, the weight ratio of the ammonium scavenger to the mixture of Step A will range from about 0.5: 1 to about 100: 1. The weight ratio of ammonium scavenger to the mixture of Step A may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the weight ratio of ammonium scavenger to the mixture of Step A may range from about 1: 1 to about 20: 1, such as between about 10: 1 and about 20: 1. For example, the weight ratio of the ammonium scavenger to the mixture of Step A may be about 2.5: 1. Alternatively, the weight ratio of the ammonium scavenger to the mixture of Step A may be about 10: 1.

( ii) solvent

[0073] The solvent may be as defined above under the description of Section (I)(c) and any embodiments thereof. In particular, the solvent may be selected from the group consisting of aliphatic hydrocarbons, methyl acetate, isopropyl acetate, and tert-butyl acetate. For example, the solvent may be an aliphatic hydrocarbon comprising n-heptane.

[0074] In general, the volume ratio of the solvent to the polysilazane will range from about 0.5: 1 to about 100: 1. The volume ratio of the solvent to the polysilazane may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the volume ratio of the solvent to the polysilazane may range from about 5: 1 to about 20: 1, such as between about 10:1 and about 20: 1.

( Hi) reaction conditions

[0075] The reaction of Step B may be conducted at a temperature that allows the solvent to reflux. Reflux depends on the solvent, pressure of the reaction, and the concentration of reagents, among other factors. In general, the temperature may range from about 30 °C to about 200°C. The temperature of the reaction may range between about 30 °C and about 40 °C, between about 40 °C and about 50 °C, between about 50 °C and about 60 °C, between about 60 °C and about 70 °C, between about 70 °C and about 80 °C, between about 80 °C and about 90 °C, between about 90 °C and about 100 °C, between about 100 °C and about 110 °C, between about 110 °C and about 120 °C, between about 120 °C and about 130 °C, between about 130 °C and about 140 °C, between about 140 °C and about 150 °C, between about 150 °C and about 160 °C, between about 160 °C and about 170 °C, between about 170 °C and about 180 °C, between about 180 °C and about 190 °C, or between about 190 °C and about 200 °C. The reaction generally will be conducted under inert atmosphere, for example under nitrogen, argon or helium.

[0076] Generally, the reaction is allowed to proceed for a sufficient period of time until the reaction is complete, as determined by any method known to one skilled in the art. The reaction may be allowed to proceed for a time that ranges from about 10 minutes to about 8 hours. For example, the duration of the reaction may range from about 10 minutes to about 30 minutes, from about 30 minutes to about 1 hour, from about 1 hour to about 2 hours, from about 2 hours to about 3 hours, from about 3 hours to about 4 hours, from about 4 hours to about 5 hours, from about 5 hours to about 6 hours, from about 6 hours to about 7 hours, or from about 7 hours to about 8 hours. In particular, the duration of the reaction may range from about 30 minutes to about 4 hours.

[0077] The purified polysilazane may have a yield of at least about 60%. For example, the purified polysilazane may have a yield of at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99%.

(c) Step C of the process

[0078] The method comprises Step C, which involves separating the purified

polysilazane. The separation may occur after Step B, and/or involve separating the ammonium salt from the mixture of Step A before Step B.

[0079] The separation may comprise filtering. A mixture of Step A may be vigorously stirred and then the ammonium salt may be filtered off, for example using filter frits having pore size of about 500 nm and diatomaceous earth (Celite™) . [0080] Alternatively, the separation may comprise centrifuging the mixture. One of skill in the art is capable of selecting the suitable centrifugation speed and the duration of effect separation of the ammonium salt from the mixture of Step A or the purified polysilazane from the mixture of Step 3.

[0081] The separation may comprises washing the mixture of Step A or Step B with an about 1: 1 to about 20: 1 volume ratio of an aqueous proton acceptor to the mixture of Step A or Step B.

[0082] In general, the proton acceptor has a pKa of between about 7 and about 13, preferably between about 8 and about 10. Representative proton acceptors that may be employed include, but are not limited to, borate salts (such as, for example, Na₃B0₃), di- and tri-basic phosphate salts (such as, for example, Na₂HP0₄ and Na₃P0₄), bicarbonate salts (such as, for example, NaHC0₃, KHC0₃, mixtures thereof, and the like), hydroxide salts (such as, for example, NaOH, KOH, mixtures thereof, and the like), carbonate salts (such as, for example, Na₂C0₃, K₂C0₃, mixtures thereof, and the like), organic bases (such as, for example, pyridine, triethylamine, diisopropylethylamine, N-methylmorpholine, Ν,Ν-dimethylaminopyridine, and mixtures thereof), organic buffers (such as, for example, N-(2-acetamido)-2-aminoethane sulfonic acid (ACES), N-(2-acetamido)-iminodiacetic acid (ADA), N,N-bis(2- hydroxyethyl)glycine (BICINE), 3-(cyclohexylamino)-l-propanesulfonic acid (CAPS),

2-(cyclohexylamino) ethanesulfonic acid (CHES), 4-(2-hydroxyethyl)-l- piperazinepropanesulfonic acid (EPPS), 4-(2-hydroxyethyl)piperazine-l -ethanesulfonic acid (HEPES), 2-(4-morpholinyl) ethanesulfonic acid (MES), 4-morpholinepropanesulfonic acid (MOPS), 1,4-piperazinediethanesulfonic acid (PIPES), [(2-hydroxy-l,l- bis(hydroxymethyl)ethyl)amino]-l-propanesulfonic acid (TAPS), 2-[(2-hydroxy-l,l- bis(hydroxymethyl)ethyl)amino]ethanesulfonic acid (TES), salts and/or mixtures thereof, and the like), and combinations thereof. In particular, the aqueous proton acceptor may be selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, aqueous ammonia, and combinations thereof.

[0083] In general, the volume ratio of the aqueous proton acceptor to the mixture of Step A or Step B will range from about 0.5: 1 to about 100: 1. The volume ratio of the aqueous proton acceptor to the mixture of Step A or Step B may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the volume ratio of the aqueous proton acceptor to the mixture of Step A or Step B may range from about 1:5 to about 1: 15, such as between about 1: 10.

[0084] The concentration of the aqueous proton acceptor may range between about 0.5 N and about 10 N, such as between about 0.5 N and about 1 N, between about 1 N and about 2 N, between about 2 N and about 3 N, between about 3 N and about 4 N, between about 4 N and about 5 N, between about 5 N and about 6 N, between about 6 N and about 7 N, between about 7 N and about 8 N, between about 8 N and about 9 N, or between about 9 N and about 10 N. In particular, the concentration of aqueous proton acceptor may be about 2 N.

(Ill) Compositions

[0085] The present disclosure provides compositions comprising combinations of a compound comprising Formula (II) and an ammonium scavenger comprising Formula (IV).

[0086] The compound of Formula (II) may be as defined above under the description of Section (I), and any embodiments thereof.

[0087] The ammonium scavenger may be as defined above under the description of Section (II), and any embodiments thereof. In particular, the ammonium scavenger may be selected from the group consisting of 3-(aminopropyl)triethoxysilane, 3- (aminopropyl)methoxysilane, 3-(aminopropyl)tripropoxysilane, and N-[3- (trimethoxysilyl)propyl]ethylenediamine).

[0088] In general, the weight ratio of ammonium scavenger to the compound of Formula (II) will range from about 0.5: 1 to about 100: 1. The weight ratio of ammonium scavenger to the compound of Formula (II) may range from about 0.5: 1 to about 2: 1, from about 2: 1 to about 5: 1, from about 5: 1 to about 25: 1, or from about 25: 1 to about 100: 1. Also the weight ratio of ammonium scavenger to the compound of Formula (II) may range between about 1:99 and about 20:80. For example, the weight ratio of the ammonium scavenger to the compound of Formula (II) may be about 2.5:97.5. Alternatively, the weight ratio of the ammonium scavenger to the compound of Formula (II) may be about 10:90.

[0089] The composition may further comprise an ammonium salt, such as ammonium chloride. The amount of ammonium chloride present in the composition may range between about 0.01 wt.% and about 10 wt.% of the total composition, such as between about 0.01 wt.% and about 0.05 wt.% of the total composition, between about 0.05 wt.% and about 0.1 wt.% of the total composition, between about 0.1 wt.% and about 0.5 wt.% of the total composition, between about 0.5 wt.% and about 1 wt.% of the total composition, between about 1 wt.% and about 2 wt.% of the total composition, between about 2 wt.% and about 3 wt.% of the total composition, between about 3 wt.% and about 4 wt.% of the total composition, between about 4 wt.% and about 5 wt.% of the total composition, between about 5 wt.% and about 6 wt.% of the total composition, between about 6 wt.% and about 7 wt.% of the total composition, between about 7 wt.% and about 8 wt.% of the total composition, between about 8 wt.% and about 9 wt.% of the total composition, or between about 9 wt.% and about 10 wt.% of the total composition.

[0090] The present disclosure also provides a composition, comprising

Formula (II),

(I I)

wherein:

n is greater than 2; and

wherein the composition is substantially free of ammonium salts. DEFINITIONS

[0091] The compounds described herein have asymmetric centers. Compounds of the present disclosure containing an asymmetrically substituted atom may be isolated in optically active or racemic form. All chiral, diastereomeric, racemic forms and all geometric isomeric forms of a structure are intended, unless the specific stereochemistry or isomeric form is specifically indicated.

[0092] As used herein, the terms "about" and "approximately" designate that a value is within a statistically meaningful range. Such a range can be typically within 20%, more typically still within 10%, and even more typically within 5% of a given value or range. The allowable variation encompassed by the terms "about" and "approximately" depends on the particular system under study and can be readily appreciated by one of ordinary skill in the art. [0093] As used herein, the term "w/w" designates the phrase "by weight," "weight percent," or "wt. %," and is used to describe the concentration of a particular substance in a mixture or solution.

[0094] As used herein, the term "ml/kg" designates milliliters of composition per kilogram of formula weight.

[0095] As used herein, the term "cure" or "curing" refers to a change in state, condition, and/or structure in a material that is usually, but not necessarily, induced by at least one variable, such as time, temperature, moisture, radiation, presence and quantity in such material of a catalyst, enhancer, accelerator or the like. The terms cover partial as well as complete curing.

[0096] By "oligomer" is meant any molecule or chemical compound which comprises several repeat units, generally from about 2 to 10 repeat units. "Polymer" or "copolymer", as used herein, means a molecule or compound which comprises a large number of repeat units, generally greater than about 10 repeat units.

[0097] As used herein, the term "monomer" refers to any chemical compound that is capable of forming a covalent bond with itself or a chemically different compound in a repetitive manner. The repetitive bond formation between monomers may lead to a linear, branched, super- branched, or three-dimensional product. Furthermore, monomers may themselves comprise repetitive building blocks, and when polymerized the polymers formed from such monomers are then termed "blockpolymers." Monomers may belong to various chemical classes of molecules including organic, organometallic or inorganic molecules. The molecular weight of monomers may vary greatly between about 40 Daltons and 20,000 Daltons. However, especially when monomers comprise repetitive building blocks, monomers may have even higher molecular weights. Monomers may also include additional reactive groups

[0098] Contemplated polymers may also comprise a wide range of functional or structural moieties, including aromatic systems, and halogenated groups. Furthermore, appropriate polymers may have many configurations, including a homopolymer, and a heteropolymer. Moreover, alternative polymers may have various forms, such as linear, branched, super-branched, or three-dimensional. The molecular weight of contemplated polymers spans a wide range, typically between 400 Daltons and 400,000 Daltons or more.

[0099] "Prepolymer" refers to polymeric structures formed by the processes in the present disclosure are long term-stable liquids, and possess only moderate odors, which mostly arise from the use of solvents. In the solid form, these polymerized materials may be handled similarly to thermosetting or thermoplastic processes. Molecular weight may vary from about 2,000 g/mol up to as much as 100,000 g/mol, depending on process. The density of the prepolymers is normally around 1 g/cm³.

[00100] The polymerization processes include, but are not limited to, step-growth polymerization, polyaddition, and polycondensation. More specifically, polymerization can be initiated by mechanisms, such as acid- or base-catalysis, or free radical polymerization. It may comprise ring-opening copolymerization, and the formation of inorganic and/or organic polymer networks. The actual mechanisms of polymerization depend on the functional groups of the reacting polymeric and monomeric compounds, as well as inherent steric effects. Conceptually new materials can be formed by adding non-conventional starting materials into the

polymerization process, such as ammonia.

[00101] The compounds described herein may have asymmetric centers.

Compounds of the present disclosure containing an asymmetrically substituted atom may be isolated in optically active or racemic form. All chiral, diastereomeric, racemic forms and all geometric isomeric forms of a structure are intended, unless the specific stereochemistry or isomeric form is specifically indicated.

[00102] The term "acyl," as used herein alone or as part of another group, denotes the moiety formed by removal of the hydroxy group from the group COOH of an organic carboxylic acid, e.g., RC(O)-, wherein R is R¹, R^-, R^N-, or R^-, R¹ is hydrocarbyl, hetero substituted hydrocarbyl, or heterocyclo, and R is hydrogen, hydrocarbyl, or substituted hydrocarbyl.

[00103] The term "acyloxy," as used herein alone or as part of another group, denotes an acyl group as described above bonded through an oxygen linkage (O), e.g., RC(0)0- wherein R is as defined in connection with the term "acyl."

[00104] The term "allyl," as used herein not only refers to compound containing the simple allyl group (CH₂=CH-CH₂-), but also to compounds that contain substituted allyl groups or allyl groups forming part of a ring system.

[00105] The term "alkyl" as used herein describes groups which are preferably lower alkyl containing from one to eight carbon atoms in the principal chain and up to 20 carbon atoms. They may be straight or branched chain or cyclic and include methyl, ethyl, propyl, isopropyl, butyl, hexyl and the like.

[00106] The term "alkenyl" as used herein describes groups which are preferably lower alkenyl containing from two to eight carbon atoms in the principal chain and up to 20 carbon atoms. They may be straight or branched chain or cyclic and include ethenyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and the like.

[00107] The term "alkynyl" as used herein describes groups which are preferably lower alkynyl containing from two to eight carbon atoms in the principal chain and up to 20 carbon atoms. They may be straight or branched chain and include ethynyl, propynyl, butynyl, isobutynyl, hexynyl, and the like.

[00108] The term "aromatic" as used herein alone or as part of another group denotes optionally substituted homo- or heterocyclic conjugated planar ring or ring system comprising delocalized electrons. These aromatic groups are preferably monocyclic (e.g., furan or benzene), bicyclic, or tricyclic groups containing from 5 to 14 atoms in the ring portion. The term "aromatic" encompasses "aryl" groups defined below.

[00109] The terms "aryl" or "Ar" as used herein alone or as part of another group denote optionally substituted homocyclic aromatic groups, preferably monocyclic or bicyclic groups containing from 6 to 10 carbons in the ring portion, such as phenyl, biphenyl, naphthyl, substituted phenyl, substituted biphenyl, or substituted naphthyl.

[00110] The terms "carbocyclo" or "carbocyclic" as used herein alone or as part of another group denote optionally substituted, aromatic or non-aromatic, homocyclic ring or ring system in which all of the atoms in the ring are carbon, with preferably 5 or 6 carbon atoms in each ring. Exemplary substituents include one or more of the following groups: hydrocarbyl, substituted hydrocarbyl, alkyl, alkoxy, acyl, acyloxy, alkenyl, alkenoxy, aryl, aryloxy, amino, amido, acetal, carbamyl, carbocyclo, cyano, ester, ether, halogen, heterocyclo, hydroxy, keto, ketal, phospho, nitro, and thio.

[00111] The terms "halogen" or "halo" as used herein alone or as part of another group refer to chlorine, bromine, fluorine, and iodine.

[00112] The term "heteroatom" refers to atoms other than carbon and hydrogen.

[00113] The term "heteroaromatic" as used herein alone or as part of another group denotes optionally substituted aromatic groups having at least one heteroatom in at least one ring, and preferably 5 or 6 atoms in each ring. The heteroaromatic group preferably has 1 or 2 oxygen atoms and/or 1 to 4 nitrogen atoms in the ring, and is bonded to the remainder of the molecule through a carbon. Exemplary groups include furyl, benzofuryl, oxazolyl, isoxazolyl, oxadiazolyl, benzoxazolyl, benzoxadiazolyl, pyrrolyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, indolyl, isoindolyl, indolizinyl, benzimidazolyl, indazolyl, benzotriazolyl, tetrazolopyridazinyl, carbazolyl, purinyl, quinolinyl, isoquinolinyl, imidazopyridyl, and the like. Exemplary substituents include one or more of the following groups: hydrocarbyl, substituted hydrocarbyl, alkyl, alkoxy, acyl, acyloxy, alkenyl, alkenoxy, aryl, aryloxy, amino, amido, acetal, carbamyl, carbocyclo, cyano, ester, ether, halogen, heterocyclo, hydroxy, keto, ketal, phospho, nitro, and thio.

[00114] The terms "heterocyclo" or "heterocyclic" as used herein alone or as part of another group denote optionally substituted, fully saturated or unsaturated, monocyclic or bicyclic, aromatic or non-aromatic groups having at least one heteroatom in at least one ring, and preferably 5 or 6 atoms in each ring. The heterocyclo group preferably has 1 or 2 oxygen atoms and/or 1 to 4 nitrogen atoms in the ring, and is bonded to the remainder of the molecule through a carbon or heteroatom. Exemplary heterocyclo groups include heteroaromatics as described above. Exemplary substituents include one or more of the following groups: hydrocarbyl, substituted hydrocarbyl, alkyl, alkoxy, acyl, acyloxy, alkenyl, alkenoxy, aryl, aryloxy, amino, amido, acetal, carbamyl, carbocyclo, cyano, ester, ether, halogen, heterocyclo, hydroxy, keto, ketal, phospho, nitro, and thio.

[00115] The terms "hydrocarbon" and "hydrocarbyl" as used herein describe organic compounds or radicals consisting exclusively of the elements carbon and hydrogen. These moieties include alkyl, alkenyl, alkynyl, and aryl moieties. These moieties also include alkyl, alkenyl, alkynyl, and aryl moieties substituted with other aliphatic or cyclic hydrocarbon groups, such as alkaryl, alkenaryl and alkynaryl. Unless otherwise indicated, these moieties preferably comprise 1 to 20 carbon atoms.

[00116] The term "protecting group" as used herein denotes a group capable of protecting a particular moiety, wherein the protecting group may be removed, subsequent to the reaction for which the protection is employed, without disturbing the remainder of the molecule. Where the moiety is an oxygen atom (and hence, forming a protected hydroxy), exemplary protecting groups include ethers (e.g., allyl, triphenylmethyl (trityl or Tr), p-methoxybenzyl (PMB), p-methoxyphenyl (PMP)), acetals (e.g., methoxymethyl (MOM),

β-methoxyethoxymethyl (MEM), tetrahydropyranyl (THP), ethoxy ethyl (EE), methylthio methyl (MTM), 2-methoxy-2-propyl (MOP), 2-trimethylsilylethoxymethyl (SEM)), esters (e.g., benzoate (Bz), allyl carbonate, 2,2,2-trichloroethyl carbonate (Troc), 2-trimethylsilylethyl carbonate), silyl ethers (e.g., trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), triphenylsilyl (TPS), t-butyldimethylsilyl (TBDMS), t-butyldiphenylsilyl (TBDPS) and the like. When the moiety is an nitrogen atom (and hence, forming a protecting amine) exemplary protecting groups include benzyl, p-methoxyphenyl (PMP), 3,4-dimethoxybenxyl (PMB)), n- silyl groups, esters (e.g., benzoate (Bz), carbonyl (e.g. p-methoxybenzyl carbonyl (Moz), tert- butyloxycarbonyl (BOC), 9-fluorenylmethyloxycarbonyl (FMOC)), acetyl, carbamates, n-silyl groups and the like. A variety of protecting groups and the synthesis thereof may be found in "Protective Groups in Organic Synthesis" by T.W. Greene and P.G.M. Wuts, John Wiley & Sons, 1999.

[00117] The "substituted hydrocarbyl" moieties described herein are hydrocarbyl moieties which are substituted with at least one atom other than carbon, including moieties in which a carbon chain atom is substituted with a heteroatom such as nitrogen, oxygen, silicon, phosphorous, boron, or a halogen atom, and moieties in which the carbon chain comprises additional substituents. These substituents include alkyl, alkoxy, acyl, acyloxy, alkenyl, alkenoxy, aryl, aryloxy, amino, amido, acetal, carbamyl, carbocyclo, cyano, ester, ether, halogen, heterocyclo, hydroxy, keto, ketal, phospho, nitro, and thio.

[00118] When introducing elements of the present disclosure or the exemplary embodiments(s) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[00119] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs at the time of filing. If specifically defined, then the definition provided herein takes precedent over any dictionary or extrinsic definition. Further, unless otherwise required by context, singular terms shall include pluralities, and plural terms shall include the singular. Herein, the use of "or" means "and/or" unless stated otherwise. All patents and publications referred to herein are incorporated by reference. EXAMPLES

[00120] The following examples are included to demonstrate embodiments of the disclosure. It should be appreciated by those of skill in the art that the techniques disclosed in the examples represent techniques discovered by the inventors to function well in the practice of the disclosure. Those of skill in the art should, however, in light of the present disclosure, appreciate that many changes may be made in the specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the disclosure; therefore, all matter set forth is to be interpreted as illustrative and not in a limiting sense.

Example 1. Attempted polysilazane synthesis.

[00121] An experiment was conducted to form polysilazanes by following reaction conditions as disclosed in the art. The reaction did not form a polymer, instead the reaction stopped at the monomeric and dimeric stage and did not progress to forming complete polymers. Also, an ammonium salt formed during reaction was difficult to remove from the reaction mixture, rendering the silazane product unsuitable as a resin constituent.

[00122] Specifically, a first reaction was conducted, whereby 1.5-kg mixture of methylsilanediamine was reacted with dichloro(methyl)silane (DMS) at -70 C in ammonia and isopropyl acetate for 1 hour, followed by slow warming to room temperature for about 6 hours, as depicted below:

CH₃

CH₃ + 4 NH₃ CH₃ H₂N-Si-CH₃

Ci-^i-CH, H₂N-Si-CH₃ NH →^ No further

- 2NH₄CI J u _<_■ polymerization

CI NH₂ H₂N-Si-CH₃

CH₃

[00123] It was determined that this reaction produced a dimer. As indicated in the

Fourier transform infrared (FTIR) spectrum at Figure 1, methylsilanediamine was formed, verifying that the reaction of Example 1 stopped before producing the desired polysilane product. The FTIR transitions were 3136 cm^"1 and 3046 cm^_1for the -NH₂ stretch, 2960 cm^"1 for the aliphatic C-H (-CH₃) stretch, 2162 cm^"1 for the Si-H stretch, 1404 cm^for -CH₂- , 1258 cm^"1 for the Si-CH₃ (in contrast to C-CH₃, which occurs around 1390 cm^"1), 1060-1040 cm^"1 for the NH- Si-NH transitions, and 835 cm^"1 for Si-CH₃. The cluster of peaks at 1060-1040 cm^"1 may also arise from a Si-NH-Si transition, which indicated a small amount of dimers, such as H₂N- SiHCH₃-NH-SiHCH₃-NH₂. [00124] In conclusion, further experiments were needed to produce polysilazane rather than monomeric and dimeric intermediates, and to explore removal of the NH₄C1 side product.

Example 2. Further attempted polysilazane synthesis.

[00125] Alternatively, the reaction of Example 1 was conducted using a different combination of starting materials and reaction conditions. This combination of features also stopped before producing the desired polysilazane.

[00126] A reaction analogous to Example 1 was conducted using

dichloro(methyl)(vinyl)silane (DMVS) with ammonia at -70°C in isopropyl acetate for 1 hour. After slowly warming the reaction mixture to room temperature for 6 hours, the reaction yielded methy 1( vinyl) silanediamine without further polymerization, as shown below:

<PH₂

,CH_{2 u} CH₂ ^H?

HC' + 4 NH3 HC' H₂N-Si-CH₃

CI-S1-CH3 _{K IU} ' H₂N-Si-CH₃ NH — K→ No further

6, - ^2NH^^CI NH₂ H₂N-Si-CH₃ Polymerⁱzatⁱon

^HC*CH₂

[00127] Figure 2 depicts the FTIR spectrum for bis-

(chloro methy lvinylsilaneamine), verifying that the reaction of Example 2 also only produced dimers and stopped before producing the desired polysilazane. In particular, the FTIR transitions were 3054 cm^"1 for the -NH₂ stretch, 3014 cm^"1 for the vinylic C-H stretch, 2965 cm^"1 for the aliphatic C-H (-CH₃) stretches, 1506 cm^"1 for the vinylic C=C stretch, 1404 cm^"1 for -CH₂-, 1258 cm^"1 for S1-CH₃ (in contrast to -CH₃, which occurs around 1390 cm^"1), 1060-1040 cm^"1 for the NH-Si-NH transitions, 818 cm^"1 for S1-CH₃, and 683 cm^"1 for Si-Cl.

[00128] The reaction product had the additional problem in that residual ammonium chloride (NH₄CI) was released during the final networking reactions, resulting in a hardened white coating. Filtration and centrifugation of these reaction products caused gradual polymerization, thereby releasing more NH₄CI crystals. While reactions were instructive, additional methods needed to be tried to achieve the correct finished product. Example 3. Polysilazane synthesis.

[00129] To attain polymerization and remove the ammonium salt side product, the reactions were repeated using liquid ammonia (NH₃ (lq)) and three different silanes in combination: dichloro(methyl)silane (DMS), dichloro(methyl)(vinyl)silane (DMVS), and dichlorodimethylsilane (DDS).

H _Hr ^CH2 ?^Η3

CI-S1-CH3 I CI-Si-CHs CI CI-Si-CHs

CI

dichloro(methyl)silane dichloro(methyl)(vinyl)silane dichlorodimethylsilane

(DMS) (DMVS) (DDS) The dichloroorganosilanes reacted according to the following general formula:

CI₂SiR¹ R² + 2NH₃

+ NH₄CI

[00130] Organic silanediamines were formed as intermediates, but unlike

Examples 1 and 2, these dimers were not the final product. Rather, the dimers continued to react until the polysilazane was formed. Additionally, in comparison, the amount of liquid ammonia was minimized in the reaction at normal pressure. No other solvents were added to this reaction. The molar ratio of liquid ammonia and organodichlorosilane was at least about 2: 1.

[00131] Gaseous ammonia was liquefied at -36 °C to -40 °C in a three-necked flask equipped with a low temperature (-45 °C) reflux condenser. The organodichlorosilanes DMS, DMVS, and DDS were mixed without a solvent and in any desired ratio and then added to the liquid ammonia via syringe. Adding the first 10% of the mixture of organic dichloro silanes resulted in a vigorous reaction, causing the liquefied ammonia to boil at -33 °C. Ammonia was recycled into the reaction mixture by using the low temperature reflux condenser at -45 °C. After adding the first 10% of organodichlorosilanes, the remaining 90% of organodichlorosilanes caused only modest boiling of the liquid NH₃, which indicated that subsequent reactions were less vigorous and released less heat than the initial reaction.

[00132] From the beginning of reaction, white NH₄C1 formed. After all organodichlorosilane was added, the low temperature reflux condenser was kept at -45 °C until the boiling stopped. After remaining another 30 minutes at < -34 °C in the condenser, the reaction mixture was warmed to ambient temperature. The liquid ammonia boiled off the reaction mixture was recycled by condensing it into a second reactor unit.

[00133] The FTIR spectra of Figures 5-7 verified that the above reaction produced the desired polysilazanes. Figure 5 depicts the FTIR spectrum of a polysilazane (20:80 (mol/mol) DMS/DMVS) after three consecutive washings of the methyl acetate solution of the polysilazane with 10: 1 v/v 2 N NaOH (aq). The FTIR transitions were 3382 cm^"1 for the -NH stretch, 3042 cm^"1 for the vinylic CH stretch, 2948 cm^"1 for the aliphatic CH (-CH₃) stretch, 2135 cm^"1 for the Si-H stretch, 1596 cm^"1 for the C=C stretch, 1404 cm^"1 for -CH₂-, 1252 cm^"1 for the Si-CH₃ stretch, 1060-1040 for the NH-Si-NH transitions, 917 cm^"1 for the Si-NH-Si transitions, and 758 for the Si-C stretch. The Si-H vibration remaining from residual starting material was discernible.

[00134] As a further example, Figure 6 depicts the FTIR spectrum for a polysilazane (100% DMS). For work-up, the sample was only filtered. The FTIR transitions were 3370 cm^"1 for the -NH stretch, 2952 cm^"1 for the aliphatic CH (-CH₃) stretch, 2112 cm^"1 for the Si-H stretch, 1404 cm^"1 for -CH₂-, 1251 cm^"1 for Si-CH₃, 1159 cm^"1 for the NH-Si-NH transitions, 883 cm^"1 for the Si-NH-Si transitions, and 762 cm^"1 for the Si-C stretch. The Si-H vibration was much larger for this spectrum than for the spectrum at Figure 5, indicating that only about half of the Si-H bonds reacted with NH₃, leading to a molar ratio of about 2.5 for the silicon-bonded amine groups in the polysilazane network.

[00135] Moreover, Figure 7 depicts the FTIR spectrum for poly(methyl)silazane formed from the reaction of sodium amide and dichloro(methyl)silane. The FTIR transitions were 3600-3000 cm^"1 for the SiO-H stretch, 2960 cm^"1 for the aliphatic CH (-CH₃) stretch, 2155 cm^"1 for the Si-H stretch, 1400 cm^"1 for -CH₂-, 1256 cm^"1 for the Si-CH₃ stretch, 1060-1040 cm^"1 for the NH-Si-NH transitions, 866 cm^"1 for the Si-NH-Si transitions, and 758 cm^"1 for the Si-C stretch. Si-OH was formed either via reaction of Si-H with oxygen or with residual water/sodium hydroxide in sodium amide.

[00136] It is believed that NH₄C1 catalyzes the formation of polysilazanes from monomeric and oligomeric organic silanediamines and catalyzed the replacement of Si-H bonds with amine groups. Evaporating the liquid ammonia concentrated the NH₄CI catalyst.

Consequently, heating this mixture was not required to complete polymerization. In particular, it is believed that reaction at the Si-H bonds further networks the polysilazane products:

The Si-Cl bond then reacts with ammonia.

NH₂ NH₂

I H I H ? H ? H

-|-Si-N-Si-N† + 2NH₃ + 2NH₄CI -Si-N-Si-N† + 4NH₃ + 2H₂ , I H I H ,

-fSi-N-Si-N-)- + 2NH₄CI

R² R² R² R² R² R²

It was observed that in the presence of NH₄CI, a three-dimensional network formation was catalyzed, leading to finished polysilazane.

Example 4. Removing ammonium chloride from the polysilazane reaction product.

[00137] It is believed that residual ammonium chloride functioned as an effective polymerization catalyst, as discussed above in Example 3, but ammonium chloride was ultimately detrimental to the clarity of coatings after curing. NH₄CI is known to result in a coating with unacceptable clarity. Therefore, it is desirable to have a method for removing ammonium chloride after the desired degree of polymerization is attained, which may be after the coating is fully cured. Consequently, two methods were explored singly or in combination for removing the ammonium chloride: ex-situ aqueous extraction and in-situ ammonium scavenging. Following either procedure, the yield of the resulting polymers was nearly quantitative (> 95%).

[00138] In one example of aqueous extraction, the reaction mixture from Example

2 was diluted with n-heptane a volume ratio of about 10 to 20. The NH₄CI was only minimally soluble at ambient temperature in the mixture. The biphasic system was vigorously stirred and then the NH₄CI was filtered using filter frits (pore size of about 500 nm). Alternatively diatomaceous earth or centrifugation was used to separate the biphasic system. The n-heptane solvent was then removed from the mixture under reduced pressure.

[00139] Instead of (or in addition to) filtering or centrifugation, mixtures of less than 20 mol% Si-H were freed from most NH₄CI by extracting the solvent layer at least three times with 2N NaOH (aq). This procedure also worked with higher Si-H concentrations, but when synthesizing larger quantities of polysilazanes the aqueous extraction tended to oxidize Si- H bonds to silanols (Si-OH). For example, the FTIR spectrum of Figure 3, indicated

diamino(methyl) silanol via a broad absorption band around 3300-3100 cm^"1 for the -OH stretch, 3147 cm^"1 and 3042 cm^"1 for the -NH₂ stretches, 2964 cm^"1 for the aliphatic C-H (-CH₃) stretch, 1732 cm^"1 and 1596 cm^"1 for solvent residues, 1403 cm^"1 for -CH₂-, 1259 cm^"1 for Si-CH₃, 1060- 1040 cm^"1 for the NH-Si-NH transitions, and 746 for the Si-C stretch. As a further example, Figure 4 depicts the FTIR spectrum of a mixture of methy 1( vinyl) silanediamine and

diamino(methyl)silanol after washing with water. The original mixture was 40:60 (mol/mol) DMS/DMVS. The Si-H groups were completely transformed into Si-OH in a very vigorous reaction.

[00140] In another example using the in-situ removal of ammonium chloride with a scavenger, the polysilazane having trace amounts of NH₄C1 was mixed with (3- aminopropyl)triethoxysilane (APTES). Since aliphatic amines were better bases than ammonia, hydrogen chloride was transferred to the -NH₂ group of APTES, which prevented NH₄CI from precipitating.

[00141] Mixtures of 20% DMVS and 80% DMS cured very slowly, taking about

24 hours at ambient temperature, and formed cloudy polymer deposits. Adding APTES (> 2.5 wt. %) led to completely transparent (clear and non-cloudy) polysilazane materials that cured at ambient temperature and up to about 100 °C. In some samples, the workup used about 10 wt.% APTES.

[00142] APTES bound the remaining HC1 without forming a precipitate. The reaction product then became completely transparent after adding APTES and remained so after being mixed with other resin components and during curing. In this way, coatings formed from the polysilazanes described herein were clear and without cloudiness formed from ammonium chloride precipitation during curing.

Example 5. Reaction of the polysilazane product with primary amines.

[00143] The polysilazane product was further reacted with primary amines to modify its chemical properties. In this Example, the purified polysilazane product of Example 4 was boiled with a stoichiometric amount of methylamine in heptane (1 mole methylamine per 1 mole Si). The reaction proceeded for about 1 hour to about 2 hours until no more ammonia evolved. This sequence of reactions led to an about 50% Si-H substitution, which was higher than the substitution observed in Examples 1-4.

[00144] Generally, the reaction is as follows:

wherein R 2 is as defined herein and R 3 is any alkyl group, for example methyl.

[00145] Mixtures of 60-80 wt.% dichlorodimethylsilane (DDS) and 40-20 wt.% dichloro(methyl)silane (DMS) showed materials properties similar to commercially available polysilazanes, especially after reacting methylamine with the polydimethylsilazane by refluxing in heptane for 2 hours. Thus, reacting polysilazanes with primary amines modulated the properties of the initial polymerization product.

[00146] While specific embodiments have been described above with reference to the disclosed embodiments and examples, such embodiments are only illustrative and do not limit the scope of the disclosure. Changes and modifications can be made in accordance with ordinary skill in the art without departing from the disclosure in its broader aspects as defined in the following claims.

Claims

1. A method for preparing a compound comprising Formula (II), the method comprising:

(a) contacting one or more compounds comprising Formula (I) with anhydrous liquid ammonia under ambient pressure at a temperature below about -33 °C, wherein a compound comprising Formula (II) and ammonium chloride are formed, the amount of anhydrous liquid ammonia ranging between one and two times the stoichiometric amount of total silicon-chloride bonds in the one or more compounds comprising Formula (I), according to the following reaction scheme:

R¹

NH I H

CI₂SiR¹ R² -hSi— N-H + NH₄CI

R²

n

(I) (I I)

wherein:

R 1 and FT 2 are independently chosen from hydrogen, alkyl, alkenyl, and phenyl, wherein

n is greater than 2; and

(b) allowing the reaction mixture from step (a) to attain ambient temperature to evaporate the anhydrous liquid ammonia.

2. The method of claim 1, wherein the step (a) uses anhydrous liquid ammonia as the only solvent.

3. The method of claim 1, wherein each R 1 and R 2 are independently hydrogen, methyl, or vinyl.

4. The method of claim 3, wherein the one or more compounds comprising Formula (I) are selected from the group consisting of dichloro(methyl)silane, dichloro(methyl)(vinyl)silane, dichlorodimethylsilane, and combinations thereof.

5. The method of claim 4, wherein the one or more compounds comprising Formula (I) consist of a molar ratio ranging between about 10:90 and about 30:70 dichloro(methyl)silane to dichloro (methyl) ( vinyl) silane .

6. The method of claim 5, wherein the one or more compounds comprising Formula (I) consist of a molar ratio of about 20:80 dichloro (methyl) silane to dichloro(methyl)(vinyl)silane.

7. The method of claim 4, wherein the one or more compounds comprising Formula (I) consists of between about 60 wt.% and about 80 wt.% dichlorodimethylsilane, and about 40 wt.% and about 20 wt.% dichloro(methyl)silane.

8. The method of claim 4, wherein the one or more compounds comprising Formula (I) is dichloro (methyl) silane .

9. The method of claim 1, wherein n is greater than 2.5.

10. The method of claim 1, wherein R¹ is hydrogen.

11. The method of claim 10, further comprising:

contacting the compound of Formula (II) with a primary alkylamine NH₂R , wherein R is alkyl, in the presence of a solvent to form a mixture; and

heating the mixture to reflux for about 0.5 to about 4 hours to produce a compound comprising Formula (III),

(III)

12. The method of claim 11, wherein the solvent is selected from the group consisting aliphatic hydrocarbons, methyl acetate, isopropyl acetate, ieri-butyl acetate.

13. The method of claim 12, wherein the solvent is an aliphatic hydrocarbon comprising n- heptane.

14. The method of claim 11, wherein the primary alkylamine is methylamine.

15. A method of using an ammonium scavenger to remove an ammonium salt from a polysilazane to provide a purified polysilazane, the method comprising:

(a) mixing a polysilazane containing an ammonium salt with a volume ratio of about 10: 1 to about 20: 1 solvent;

(b) contacting the mixture of step (a) with an ammonium scavenger to convert the

ammonium salt to ammonia, wherein the ammonium scavenger is a compound comprising Formula (IV),

wherein:

R⁴ is hydrogen or alkyleneamine;

L is alkylene; and

each R⁵ is independently selected alkyl;

(c) separating the purified polysilazane.

16. The method of claim 15, wherein R⁴ is alkyleneamine.

17. The method of claim 16, wherein the alkyleneamine is ethyleneamine.

18. The method of claim 15, wherein L is propylene.

19. The method of claim 15, wherein R⁵ is selected from the group consisting of methyl, ethyl, and propyl.

20. The method of claim 15, wherein the ammonium scavenger is selected from the consisting of 3-(aminopropyl)triethoxysilane, 3-(aminopropyl)methoxysilane, 3- (aminopropyl)tripropoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine).

21. The method of claim 15, wherein the ammonium salt is ammonium chloride.

The method of claim 15, wherein the polysilazane comprises Formula (II),

wherein:

1 2

R and are independently chosen from hydrogen, alkyl, alkenyl, and

1 2

phenyl, wherein R and R may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides; and

n is greater than 2.

23. The method of claim 15, wherein the solvent is selected from the group consisting of aliphatic hydrocarbons, methyl acetate, isopropyl acetate, and ieri-butyl acetate.

24. The method of claim 23, wherein the solvent is an aliphatic hydrocarbon comprising n- heptane.

25. The method of claim 15, wherein the weight ratio of the ammonium scavenger to the mixture of step (a) ranges between about 1 : 1 and about 20: 1.

26. The method of claim 25, wherein the weight ratio of the ammonium scavenger to the mixture of step (a) is about 2.5: 1.

27. The method of claim 25, wherein the weight ratio of the ammonium scavenger to the mixture of step (a) is about 10: 1.

28. The method of claim 15, further comprising separating the ammonium salt from the mixture of step (a) before step (b).

29. The method of claim 28, wherein the separation comprises filtering the mixture of step (a).

30. The method of claim 28, wherein the separation comprises centrifuging the mixture of step (a).

31. The method of claim 28, wherein the separation comprises washing the mixture of step (a) with an about 1: 1 to about 20: 1 volume ratio of an aqueous proton acceptor to the mixture of step (a).

32. The method of claim 31, wherein the aqueous proton acceptor is selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, aqueous ammonia, and combinations thereof.

33. The method of claim 31, wherein the volume ratio of the aqueous proton acceptor to the mixture of step (a) ranges between about 1:5 to about 1: 15.

34. The method of claim 31, wherein the volume ratio of the aqueous proton acceptor to the mixture of step (a) is about 1: 10.

35. The method of claim 31, wherein the concentration of the aqueous proton acceptor ranges between about 0.5 N to about 10 N.

The method of claim 31, wherein the concentration of aqueous proton acceptor is about 2

37. The method of claim 1, further comprising using an ammonium scavenger to remove the ammonium salt from a polysilazane comprising the compound Formula (II) to provide a purified polysilazane according to any one of claims 15-36.

A method for preparing a polysilazane, the method comprising:

(a) contacting a mixture of Formula (I) selected from the group consisting of

dichloro(methyl)silane, dichloro(methyl)silane/dichloro(methyl)(vinyl)silane, dichloro(methyl)silane/dichlorodimethylsilane, and

dichloro(methyl)silane/dichloro(methyl)(vinyl)silane/dichlorodimethylsilane, with a solvent consisting of anhydrous liquid ammonia under ambient pressure at a temperature below -33 °C, wherein a polysilazane of Formula (II) and ammonium chloride are formed, the amount of anhydrous liquid ammonia ranging between one and two times the stoichiometric amount of total silicon-chloride bonds in the mixture of Formula (I), according to the following reaction scheme:

R¹

I H

CI₂SiR¹ R² - Si-N-r- + NH₄CI

R²

(I) (I I)

wherein:

R 1 and FT 2 are hydrogen, methyl, or vinyl; and

n is greater than 2; and

(b) allowing the reaction mixture from step (a) to attain ambient temperature over the duration of between about 5 and about 7 hours to evaporate the anhydrous liquid ammonia.

39. The method of claim 38, wherein the mixture of Formula (I) is

dichloro(methyl)silane/dichloro(methyl)(vinyl)silane with a molar ratio ranging between about 10:90 and about 30:70 dichloro(methyl)silane to dichloro(methyl)(vinyl)silane.

40. The method of claim 39, wherein the one or more compounds comprising Formula (I) consist of a molar ratio of about 20:80 dichloro(methyl)silane to dichloro(methyl)(vinyl)silane.

41. The method of claim 38, wherein the mixture of Formula (I) is between about 60 wt.% and about 80 wt.% dichlorodimethylsilane, and between about 40 wt.% and about20 wt.% dichloro (methyl) silane .

The method of claim 38, wherein the mixture of Formula (I) is dichloro(methyl) silane.

43. The method of claim 38, further comprising:

contacting the polysilazane of Formula (II) with a primary alkylamine NH₂R , wherein R is alkyl, in the presence of a solvent selected from the group consisting of aliphatic hydrocarbons, methyl acetate, isopropyl acetate, ieri-butyl acetate, to form a mixture; and

heating the mixture to reflux for about 0.5 to 4 hours to produce a compound comprising Formula (III),

(III)

44. A composition, comprising:

a compound comprising Formula (II

(II)

wherein:

R 1 and R 2" are independently chosen from hydrogen, alkyl, alkenyl, and phenyl, wherein R 1 and R 2 may be optionally substituted with one or more sulfonic acids, carboxylic acids, amines, or amides; and

n is 2 or greater; and

an ammonium scavenger comprising Formula (IV),

wherein:

R⁴ is hydrogen or alkyleneamine;

L is alkylene; and

each R⁵ is independently selected alkyl.

1 2

45. The composition of claim 44, wherein each R and R is independently hydrogen, methyl, or vinyl.

46. The composition of claim 44, wherein n is greater than 2.5.

47. The composition of claim 44, wherein R⁵ is selected from the group consisting of methyl, ethyl, and propyl.

48. The composition of claim 44, wherein L is propylene.

49. The composition of claim 44, wherein R⁴ is alkyleneamine.

50. The composition of claim 49, wherein the alkyleneamine is ethyleneamine.

51. The composition of claim 44, wherein the ammonium scavenger is selected from the group consisting of 3-(aminopropyl)triethoxysilane, 3-(aminopropyl)methoxysilane, 3- (aminopropyl)tripropoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine).

52. The composition of claim 44, wherein the weight ratio of the ammonium scavenger to the compound of Formula (II) ranges between about 1 :99 and about 20:80.

53. The composition of claim 52, wherein the weight ratio of the ammonium scavenger to the compound of Formula (II) is about 2.5:97.5.

54. The composition of claim 52, wherein the weight ratio of the ammonium scavenger to the compound of Formula (II) is about 10:90.

55. The composition of claim 44, further comprising an ammonium salt.

56. The composition of claim 55, wherein the ammonium salt is ammonium chloride.

57. A composition, comprising:

Formula (II),

(I I)

wherein:

n is greater than 2; and

wherein the composition is substantially free of ammonium salts.

58. The composition of claim 57, wherein each R 1 and R 2 are independently hydrogen, methyl, or vinyl.

59. The composition of claim 58, wherein n is greater than 2.5.

60. The composition of claim 57, wherein the ammonium salt is ammonium chloride.