United States Patent (19) 11 Patent Number: 4,946,919 Johnson 45 Date of Patent: Aug. 7, 1990

54 BORON CERAMICS FROM 4,258,079 3/1981 Economy et al...... 427/44 CARBORALATED DACETYLENE 4,277,588 7/1981 Naarmann et al...... 526/114 4,439,346 3/1984 Patel et al...... 252/408.1 POLYMERS 4,562,141 12/1985 Tieke ...... 430/281 (75) Inventor: Robert E. Johnson, Hoboken, N.J. 4,857,490 8/1989 Johnson ...... 501/96 73) Assignee: Hoechst Celanese Corp., Somerville, OTHER PUBLICATIONS N.J. "Polydiacetylenes Spur Activity from Commercial to 21 Appl. No.: 273,089 Theoretical”, Chemical and Engineering News, May 5, 22 Filed: Nov. 18, 1988 1988, pp. 33-37. Primary Examiner-Melvyn I. Marquis Related U.S. Application Data Attorney, Agent, or Firm-Depaoli & O'Brien 62 Division of Ser. No. 90,999, Aug. 31, 1987, abandoned. 57 ABSTRACT 51 Int. Cl...... C08F 38/00 Boron-containing ceramics are formed from organobo 52) U.S. C...... 526/285; 528/4; ron preceramic polymers which are carboralated acety 528/5 lenic polymers. The polymers can be formed by car 58) Field of Search ...... 528/4, 5; 526/285 boralating acetylenic or diacetylenic diols and condens (56) References Cited ing the diols to form carboralated polyesters. In an alternative process, polydiacetylene formed by the pol U.S. PATENT DOCUMENTS ymerization of diacetylene monomers having conju 3,097,195 7/1963 Kennerly et al...... 260/94.1 gated triple bonds are carboralated subsequent to poly 3,214,466 10/1965 Green et al...... 528/4 3,351,616 11/1967 Green et al...... 528/4 merization. A process for obtaining readily soluble 3,354,121 11/1967 Knoth, Jr. et al...... 528/4 polydiacetylenes comprises heating a diacetylene diol in 3,359,304 12/1967 Bobinski et al...... 560/190 a high boiling solvent. 3,505,409 4/1970 Bobinski et al...... 568/4 4,220,747 9/1980 Preziosi et al...... 526/285 12 Claims, No Drawings 4,946,919 1. 2 Other metallic polymers have been suggested as ce BORON CERAMICS FROM CARBORALATED ramic precursers. Thus, U.S. Pat. No. 4,581,468 forms DACETYLENE POLYMERS boron nitride by pyrolyzing B-triamino-N-tris (trialkyl silyl)borazines. U.S. Pat. No. 4,097,294 suggests that a This application is a division, of application Ser. No. 5 boron carbide ceramic is obtainable from a carborane 090,999, filed Aug. 31, 1987 now abandoned. carbon polymer. The formation of aluminum nitride fibers is disclosed FIELD OF THE INVENTION in commonly assigned, U.S. Pat. No. 4,687,657. Alumi The present invention is directed to the formation of num nitride ceramics are formed by thermal conversion boron-containing ceramics from organoboron prece 10 of poly-N-alkyliminoalanes. Ceramics comprising sili ramic polymers. The present invention is also directed con carbide and aluminum nitride solid solutions are to a novel method of forming boron-containing ceram also disclosed. These ceramic alloys are formed by ics, in particular, ceramic fibers from carboralated poly thermal conversion of a mixture of an organosilicon mers. The invention is also concerned with novel car preceramic polymer and the above-mentioned alumi boralated acetylenic polymers and methods of forming 15 num-containing polymer. Moreover, many recent pa S3. tents describe specific silicon-containing preceramic polymers which are formed into silicon carbide and/or BACKGROUND OF THE INVENTION nitride upon thermal treatment. In the search for high performance materials, consid Alternatively, ceramic fibers such as metal carbide erable interest has been focused upon carbon fibers. The 20 fibers have been formed by incorporating inorganic terms "carbon' fibers or "carbonaceous' fibers are used metallic compounds into a carbon fiber product, the herein in the generic sense and include graphite fibers as precarbonaceous polymer forming solution, the poly well as amorphous carbon fibers. mer spinning solution or the polymer fiber subsequent Industrial high performance materials of the future to spinning, and converting the metallic compounds in are projected to make substantial utilization of fiber 25 situ to metal carbides upon thermal conversion. In these reinforced composites, and carbon fibers theoretically methods, the precarbonaceous polymer acts as the have among the best properties of any fiber for use as source of carbon. high strength reinforcement. Among these desirable Important ceramics formed by such method are properties are corrosion and high temperature resis boron carbide and boron carbide-containing carbon tance, low density, high tensile strength and high modu 30 fibers. The addition of boron carbide to carbon fiber is lus. During such service, the carbon fibers commonly known to increase fiber strength and, more particularly, are positioned within the continuous phase of a resinous to substantially increase the thermo-oxidative stability matrix (e.g. a solid cured epoxy resin). Uses for carbon of carbon fibers such that the boron carbide-containing fiber reinforced composites include aerospace structural carbon fibers can withstand higher temperature envi components, rocket motor casings, deep-submergence 35 ronments than carbon fibers. Methods of incorporating vessels, ablative materials for heat shields on re-entry boron into carbon fibers to form boron carbide fibers vehicles, strong lightweight sports equipment, etc. have typically involved treating the carbon fibers with As is well known in the art, numerous processes have gaseous boron halides or impregnation with soluble heretofore been proposed for the thermal conversion of borane salts or boric oxides including boric acid, metal organic polymeric fibrous materials (e.g. an acrylic 40 lic borates and organic borates, e.g. alkyl and aryl bo multifilamentary tow) to a carbonaceous form while rates. Upon being treated with the boron compounds, retaining the original fibrous configuration substantially the fibers are heated to initiate reaction of boron with intact. During commonly practiced carbon fiber forma the carbon fibers to yield boron carbide. tion techniques, a multifilamentary tow of substantially In commonly assigned, copending application U.S. parallel or columnized carbon fibers is formed with the 45 Ser. No. 082,761, filed Aug. 7, 1987, now U.S. Pat. No. individual "rod-like” fibers lying in a closely disposed 4,832,895, May 23, 1989 boron-containing fibers are side-by-side relationship. See for instance, the following provided by forming a blend of a boron-containing commonly assigned U.S. Pat. Nos. 3,539,295; 3,656,904; polymer and a precarbonaceous polymer, shaping the 3,723,157; 3,723,605; 3,775,520; 3,818,082; 3,844,822; blend into a fiber such as by spinning and pyrolyzing to 3,900,556; 3,914,393; 3,925,524; 3,954,950; and 50 form a boron ceramic fiber. Preferably, the boron-con 4,020,273. taining polymers are prepared by the condensation of In addition to carbon fibers, there has been interest in boranes with Lewis bases. Such polymers are well the use of ceramic materials, including ceramic fibers known and prepared by condensing a borane such as for a number of high temperature, high performance diborane, pentaborane or decaborane with Lewis bases applications such as gas turbines. These applications 55 such as amines, amides, isocyanates, nitriles and phos require a unique combination of properties such as high phines. A particularly preferred borane-containing pol specific strength, high temperature mechanical prop ymer is one formed by the condensation of decaborane erty retention, low thermal and electrical conductivity, and dimethylformamide (DMF). The borane-Lewis hardness and wear resistance, and chemical inertness. base condensation polymers are known and described, Among the ceramic materials which have been sug for example, in POLYMER LETTERS, Vol. 2, pp. gested are those made from organosilicon polymers. 987-989 (1964); Chemical Society (London) Spec. Publ. Thus, polymers based on silicon, carbon and/or nitro No. 15 (1961), "Types of Polymer Combination among gen and/or oxygen have been developed. See, for exam the Non-metallic Elements', Anton B. Burg, pp. 17-31; ple, "Siloxanes, Silanes and Silazanes and the Prepara U.S. Pat. Nos. 2,925,440; 3,025,326; 3,035,949; tion of Ceramics and Glasses' by Wills et al, and "Spe 65 3,071,552; and British Patent No. 912,530. Other bo cial Heat-Resisting Materials from Organometallic Pol rane-containing polymers suggested include those dis ymers' by Yajima, in Ceramic Bulletin, Vol. 62, No. 8, closed in U.S. Pat. No. 3,441,389 wherein borane poly pp. 893-915 (1983), and the references cited therein. mers are prepared by heating a compound of the for 3 4,946,919 4. mula (RAH3)2 B10H10 or (RAH3)2 B12H12 at a tempera patents are used primarily as high energy fuels such as ture of 200-400' C. for several hours. Moreover, bora for rocket propellants. zines such as disclosed in U.S. Pat. No. 4,581,468 and It is also known to prepare a biscarborane by reacting carborane polymers such as suggested in U.S. Pat. No. diacetylene with bis(acetonitrile) decaborane to car 4,097,294 are also considered useful. 5 boralate one of the acetylenic bonds and additionally The use of organometallic polymers as precursors for reacting with bis(acetonitrile) decaborane to carbora ceramic materials is advantageous in the formation of late the second acetylenic bond. As far as is known, the ceramic fibers. It is considerably easier to spin the poly carboralated acetylenic including diacetylenic com meric materials than inorganic precursors composed of pounds and polymers as above-described have not pre inorganic metallic particles dispersed in a spinnable 10 organic matrix. It would, therefore, be desirable to find viously been suggested as precursers for boron-contain new organometallic polymers and methods of making ing ceramic materials. same which can be used as ceramic precursors. The SUMMARY OF THE INVENTION present invention is concerned with preparing organo In accordance with the present invention, a novel boron polymers which can serve as precursors for 15 boron ceramics such as boron carbide and boron nitride method is provided for preparing boron-containing and ultimately to the formation of fibers of these boron ceramic materials from organoboron preceramic poly containing ceramic materials. mers. The organoboron polymers useful in this inven One difficulty in preparing boron-containing ceram tion as ceramic precursors are carboralated polymers ics from organic precursers is the inability to incorpo which have been formed by carboralating monomeric rate sufficient boron into the organic polymer and react 20 or polymeric materials which contain acetylenic bonds. with the carbon components to form boron carbide, As discussed previously, one of the difficulties of B4C. Methods of incorporating boron-containing salts formingboron-containing ceramics, in particular, boron or boron-containing inorganic powders and the like into carbide, from organic precursors is the inability to pro precarbonaceous polymer solutions, solids, or the vide the precursor with a sufficient boron content capa formed carbon articles have proved unsuccessful in 25 ble of yielding the desired boron carbide upon pyroly providing sufficient amounts of boron to yield im zation of the precursor to the ceramic form. It would be proved boron carbide-containing ceramic materials. advantageous therefor to provide a preceramic organo The boron-containing polymers as described in the boron polymer with a high degree of carboralation. aforementioned commonly assigned, co-pending appli This is achieved in the present invention by carboralat cations have yielded boron carbide ceramics containing 30 ing an alkyne- or diyne-diol and forming polymers, e.g., greater than 40% boron. There is, however, a continu ing need to find additional preceramic organoboron polyesters, through condensation or, by carboralating a polymeric materials which yield ceramics containing polymer which contains acetylenic bonds. The car increased levels of boron. boralated acetylenic polymers of this invention contain As described previously, decaborane-containing pol 35 carborane groups along the backbone thereof. ymers such as those produced by the reaction of In the first aspect of the present invention, boron decaborane with a Lewis base are known. Additionally, ceramics are obtained by pyrolysis of organoboron organoborane polymers have been produced by poly preceramic polymers which are formed by polymeriz merizing difunctional carboralated acetylene monomers ing difunctional carboralated acetylenic monomers. It such as by condensation. has been suggested to form boron-containing ceramics Carborane which is a compound of carbon, hydrogen from carborane polymers as described in U.S. Pat. No. and boron has the empirical formula C2H12B10. While 4,097,294. Such polymers are known and are prepared there is some difference of opinion as to the molecular by a multi-step process in which a carborane unit is structure of carborane, its stability is usually attributed functionalized with polymerizable groups such as halo to a basket-shaped molecular configuration in which the 45 gen, siloxy, hydroxy, or carboxy groups and the difunc 10 boron atoms and 2 carbon atoms are arranged at the tionalized carborane subsequently polymerized. In such apices of an icosahedron. The following formula has a process, carboralation is achieved by reacting a Lewis been proposed wherein the circle indicates generalized, base-derivatized decaborane with acetylene. It would delocalized pi-bonding between the carbon and boron be easier and, thus, preferable to directly carboralate atons. 50 acetylene monomer which contains difunctional, e.g. polymerizable, groups on opposite ends of the triple bond. Unfortunately, it is not possible to carboralate Ham-C C-H No M such an acetylene monomer since many of the polymer BioH10 izable groups such as hydroxy or carboxy are electron 55 withdrawing and adversely affect the reactivity of the The carboralated monomers have been prepared by acetylenic bond for decaborane. first reacting decaborane with an electron-donor com Thus, in accordance with the first aspect of the inven pound, e.g., acetonitrile, to form a coordination com tion, organoboron preceramic polymers are provided pound, e.g. (CH3CN)2B10H12, bis-(acetonitrilo) decabo from difunctional acetylenic monomers which contain rane. The coordination compound is then reacted with at least one carbon spacer between the acetylenic car a compound having acetylenic unsaturation to form a bons and the electron withdrawing polymerizable carborane derivative. A method of forming polyester groups so as to insure carboralation of the triple bond. carboranes is disclosed in U.S. Pat. No. 3,351,616. Other Such an acetylenic monomer has the formula: patents disclosing carborane compounds include U.S. ZZ'C=CZZ wherein Z' is a hydrocarbon or substi Pat. Nos. 3,217,031; 3,247,256; 3,254,117; 3,234,288; 65 tuted hydrocarbon group containing 1 to 10 carbon 3,359,304; and 3,505,409; all of which are herein incor atoms and Z comprises a polymerizable group, for ex porated by reference. The boron-containing com ample, hydroxy, carboxy, siloxy, etc. A particularly pounds and polymers disclosed in the aforementioned preferred carbon spacer is -C=C- to provide a 4,946,919 5 6 diyne-diol monomer. Such a monomer contains conju nitriles and dinitriles, acetonitrile, propionitrile, cyano gated triple bonds. Although only one of these triple gen, malononitrile, succionitrile, gultaronitrile, adiponi bonds can be carboralted, upon polymerization such as trile and B,B'-oxydipropionitrile can be mentioned as by condensation of the diol with another reactive com examples. pound, the polymer which is formed contains a back As a preferred example of these derivatives, the coor bone of repeating units of carborane and an unreacted dination compounds of decaborane and acetonitrile may acetylenic bond which can provide a means for func be mentioned. Acetonitrile, on refluxing with decabo tionalizing the polymer in a variety of known ways. rane, forms a product of (CH3CN)2B10H12, with hydro Alternatively, in accordance with this invention, an gen being evolved as a byproduct. The bis(acetonitrilo) acetylenic polymer is formed which contains a plurality 10 decaborane compound is particularly convenient be of acetylenic bonds along the backbone which are sub cause of the unexpected ease with which acetonitrile is sequently carboralated. Polydiacetylenes are the pre displaced almost quantitatively in the coupling of the ferred polymers which are carboralated. These poly decaborane group to an acetylenic bond. Another mers are obtained from monomers containing conju Lewis base which has been used to form coordinated gated triple bonds and are polymerized to provide a 15 compounds with decaborane is dimethylsulfide to yield polymeric backbone of conjugated triple and double dimethylsulfido decaborane. bonds. Carboralation of the triple bonds provides a The reaction between the acetylenic bond and the novel preceramic organoboron polymer. decaborane derivative proceeds conveniently by reflux One problem in using polydiacetylene as a reactant ing the reactants in a hydrocarbon solvent such as ben for carboralation is the difficulty in dissolving the poly 20 zene, xylene, or toluene. mer. Often, polydiacetylene is formed by polymerizing While decaborane is the preferred boron source in the diacetylene monomer on the solid state to yield view of the high boron content of the compound, other solid, intractable polymers. Thus, in another aspect of boranes and substituted boranes may be used in the the present invention, a method of producing polyd practice of this invention. Such compounds include iacetylene which can be readily carboralated in solution 25 diborane, triborane, tetraborane, pentaborane, hexabo is provided. In accordance with this aspect of the pres rane, decaborane, and substituted and di-substituted ent invention, polydiacetylene is formed by heating derivatives thereof including alkyl, cyloalkyl, aryl, and simple derivatives of diacetylen-diol monomers in high alkyl-aryl derivatives. boiling solvents which results in the polymerization of The carboralated polymers useful in this invention as the monomer. The polymers which are formed are of 30 precursors for boron-containing ceramics ceramics can relatively low molecular weight but can be readily be formed by several methods. In one method, a com dissolved in conventional solvents and can therefor be pound containing acetylenic unsaturation and further carboralated in solution with decaborane. containing one or more polymerizable functional Processing of the carboralated diacetylene polymers groups is carboralated and the carboralated compound of this invention into preceramic articles such as fibers is 35 improved by blending the lower molecular weight or is then subsequently polymerized. In another method, a ganoboron preceramic polymers with a carbon-forming polymer containing in the backbone thereof acetylenic polymer such as polyacrylonitrile prior to spinning. unsaturation is carboralated at the acetylenic bonds. Pyrolysis of the organoboron polymer in selective In the first method, the Lewis base-decaborane deriv atmospheres yields the desired ceramic. For example, ative, C.S., bis(acetonitrile) decaborane, pyrolysis in argon or diborane yeilds boron carbiode as (CH3CN)2B10H12, is reacted with a compound having a product while pyrolysis in ammonia results in boron acetylenic unsaturation to form a carborane derivative: nitride. DETALED DESCRIPTION OF THE INVENTION 45 The carboralation of an acetylenic bond is well known and is achieved by the reaction of a decaborane derivative with a compound having acetylenic unsatu ration. The decaborane derivative is one formed by 50 reaction of decaborane with an electron-donor com wherein Z' is a hydrocarbon group containing 1 to 10 pound, E.G., Lewis base. Useful Lewis bases include carbon atoms, preferably akylene, and Z can be any of ammonia, primary and secondary amines and diamines, a very wide variety of polymerizable groups. Prefera and nitriles and dinitriles which react with decaborane bly, Z is -OR or -COOR wherein R is for example, to form the derivative with the evolution of hydrogen. 55 alkyl, aryl, acyl, or silyl. Although it is possible for R to The reaction with ammonia takes place at 120 C. and is be hydrogen, it is not recommended inasmuch as the well known in the art. Similar bonding occurs with hydrogen is reactive towards decaborane and thus, monoamines as, for example, methylamine, ethylamine, would adversely affect the carboralation reaction. n-propylamine, isopropylamine, n-butylamine, Thus, in accordance with this invention carboranyl isobutylamine, sec-butylamine, tert-butylamine, n polyols and polyacids can be formed and used in making amylamine, isoamylamine, 2-aminopentane, inter alia. polyesters by condensation with other carboranyl or As secondary amines dimethylamine, diethylamine, noncarboranyl polyols and polyacids. Prior to conden di-n-propylamine, diisopropylamine, di-n-butylamine, sation, the R groups are preferably hydrolyzed by con dissobutylamine, and di-sec-butylamine may be given as ventional means. examples. Diamines include, for example, ethylenedi 65 The carboranyl radical or radicals of the present amine, propylenediamine, tri-methylenediamine, 1,3- polymers may be in either the alcohol residue of the diaminobutane, 1,4-butanediamine, 1,5-pentanediamine, polyester or the acid residue of the polyester or both. It hexamethylendiamine, and octamethylenediamine. As has been found that in general any carboranyl glycol 4,946,919 7 8 may be reacted with a polycarboxylic acid, with may or A novel preceramic organoboron polymer prepared may not itself contain a carbonyl radical, to form the in accordance with this invention is one containing a present polymers. Similarly, it has been found that in mixture of carborane and unreacted acetylenic bonds in general any carbonanyl dicarboxylic acid may be re the backbone thereof. This polymer is useful as a prece acted with a glycol, which may or may not contain a ramic material in view of te boron content and the abil carboranyl radical, to form the polymers. Anhydrides ity to tailor the polymer by adding functionality to the and acyl chlorides of the dicarboxylic acids disclosed noncarboralated triple bond such as, for example, halo herein can also be used in place of the free acids in genation, crosslinking, etc. A preferred difunctional making the present polymers. acetylenic compound useful in forming organoboron The carboranylglycols can be reacted with dicarbox 10 preceramic polymers in accordance with this invention ylic acids containing no carboranyl radical to produce is one which contains conjugated triple bonds such that polyester polymers according to the invention. Such Z' is a -C=C-Z" group wherein in Z" is a hydrocar acids include maleic, fumaric, adipic, sebacie, succinic, bon containing one to ten carbon atoms. An example of azelaic, glutaric, phthalic, terephthalic, tetrahydroph such a difunctional diyne is 2,4-hexadiyne-1,6-diacetate thalic, tetrachlorophthalic and perflurorglutaric acids. 15 which when carboralated as described above results in Anhydrides, acyl chlorides and esters of such acids may a carboralated monomer of 4,5-carboryl-2-hexyne-1,6- also be used, such as phthalic anhydride, methyl suc diacetate. This carboralated monomer after acid hydro cinic anhydride, succinyl chloride, adipyl chloride and lysis leaves the corresponding diol and as a diol can be siccinic acid esters. Aliphatic acids having from 3 to 10 20 condensed as described above to form polyesters, poly carbon atoms are preferred. ethers, etc. ver In a similar manner the carboranyl dicarboxylic acids An alternative method of forming carboralated may be reacted with glycols, particularly alkylene gly preceramic polymers in accordance with this invention cols such as ethylene, proplylene, and butylene glycols, comprises carboralating a polymer containing acetyle or diglycols to form condensation polymers according nic unsaturation by reaction with the Lewis base to the invention. Also carboranyl glycols such as those 25 decaborane derivative as above described. Such poly disclosed above can be condensed with the carboranyl mers can be formed by reacting difunctional acetylenic acids such as those disclosed above to form condensa monomers such as acetylenic diols and dicarboxylic tion polymers having an eespecially high boron content. acids to form polyesters. Upon formation of the poly The carboranyl gylcols and dicarboxylic acids can mer, the acetylenic bonds are then carboralated. also be reacted to form condensation polymers with 30 It would be advantageous to provide a polymer sulfates, phosphates, borates, titanates, silicones, etc. which contains a great number of acetylenic bonds in Polymerization of the boron-containing diols and the backbone thereof relative to the molecular weight diacids can be carried out by techniques conventional in of the polymer. Accordingly, a preferred acetylenic the art for diol-diacid condensations, e.g., heating at polymer useful in this invention is poly(diacetylene). reflux temperature to drive off water for a period suffi 35 The diacetylene monomer may be seen to possess at cient to form a condensation polymer. The condensa least two acetylenic bonds, at least two of which acety tion can be catalyzed by acid catalysts known to the art, lenic bonds are in conjugation one with another. e.g., p-toluene sulfonic acid and Lewis acid type cata Diacetylenes which are suitable monomers for poly lyst such as zinc chloride and aluminum chloride. Or, merization conform to the general formula: the reaction may be uncatalyzed and proceed by simple R1-C=EC-C=C-R2 heating or by bubbling an inert gas, such as nitrogen or argon, through the reactants. The reaction proceeds in where R and R2 may be the same or different and may solvent or in bulk. Condensation polymers having mo comprise alkyl, aryl, alkaryl, or aralkyl groups having lecular weights within the range 500 to 5,000 or higher 45 from one to about 50 carbon atoms. R1 and R2 may, in are readily obtained. addition, have heteroatomic substitutions or unsatura In some cases, as for example where both carboxyl tions. Thus, R1 or R2 may include one or more ester, groups of the diacid are attached to the same carbon acid, alcohol, phenol, amine, amide, halogen, sulfonyl, atom, polymerization of the diol and diacid is desirably sulfoxyl, sulfinyl, silyl, siloxyl, phosphoro, phosphato, effected by ester interchange in known manner. 50 keto, aldehydo, or other moieties. In addition, metal A description of polymerizing carboranyl polyols modifications of any of the foregoing may be included and polyacids is set forth in aforementioned U.S. Pat. such as, for example, acid or phenolate salt. In addition, Nos. 3,234,288; 3,351,616; and 3,359,304. R1 or R2 or both may be ester, acid, alcohol, phenol, The acetylenic monomer may contain one or more amine, amide, halogen, sulfonyl, sulfoxyl, silyl, siloxyl, acetylenic bonds. However, not all of the acetvlenic 55 phosphoro, phosphato, keto, aldehydoor a metal salt or bonds of the monomer may be carboralated inasmuch as phenolate. In short, it is contemplated that any diacety electron withdrawing groups in the proximity of the lene may be suitable for use in the invention with the acetylenic bond may greatly reduce the reactivity of the exception of those diacetylenes wherein R1 or R2 or acetylenic bond for decaborane. Thus, a spacer group both are hydrogen. The latter compositions are not such as Z is necessary to shield the acetylenic bond suitable due to the fact that they are, in general, explo from any electron withdrawing groups such as the poly SVe. merizable diols and diacyls or other acetylenic bond. It is to be understood that the species referred to in Monomers containing nonconjugated triple bonds can this description of the invention may be either straight be fully carboralated. It should be noted, however, that chain, cyclic, aromatic, or branched. It should also be the required spacer group needed to separate the elec 65 understood that reference to diacetylenes does not fore tron withdrawing capacity of the other proximate triple close the presence of additional acetylenic bonds bond increases the carbon content of the ceramic upon therein. Thus, compositions having 3, 4, or more acety pyrolyzation of the polymer. lenic bonds are foreseen as long as at least two or more 4,946,919 9 10 of such bonds are in conjugation one with another. The present invention is particularly useful in the Furthermore, additional sites of unsaturation may be formation of boron ceramic fibers from a spinning com present such as carbon-carbon, carbon-oxygen, carbon position comprising the organoboron preceramic poly nitrogen, or other double bonds, aromatic or mer or a blend of boron-containing polymer and a pre heteroaroomatic species. Substitution with halogens, carbonaceous polymer. Polymer blends are particularly hydroxyls, amines, thiols, silyls, siloxyls, phosphates, useful if the organoboron polymer has a low molecular sulfates, sulfonates, or other functionalities is also use weight. Any known technique for spinning the organo ful. boron preceramic polymer into fiber may be used in Exemplary syntheses of diacetylenes are presented in cluding melt and solvent spinning methods. While it "Synthesis of N-(nitrophenyl)amine Substituted Diace 10 may be possible to melt spin the organoboron polymer, tylene Monomers', Garito et al, Makromolecular Che most likely the organoboron polymer will have a melt mie (in press); "Synthesis of Chiral Diacetylene Poly ing point far above the melting point of a blendable mers', Garito et al, Makromolecular Chemie (in press); precarbonaceous polymer which may be adversely ef "The Chemistry of Diacetylenes", Keter Pub. House, fected at the temperatures required for melt spinning. Jerusalem (1974); Synthesis of Nitrophenoxymethyl 15 Accordingly, a solvent spinning method is preferred. Substituted Diacetylene Monomers', Kalyanaraman, Thus, spinning into fibers is preferably accomplished Garito et al, Makromolecular Chennie, vol. 180, Jun. with either the wet or dry spinning techniques. In dry 1979: "Solid-State Synthesis and Properties of the spinning, the spinning composition issues from the spin Polydiacetylenes', Baughman et al, Annals of NYAcad ning apparatus through a spinning column wherein a emy of Science, vol. 313, (1978); "Polymerization of 20 stream of drying gas is simultaneously fed through the Diacetylene Carbonic Acid Monolayers at the Gas spinning column. The temperature of the spinning col Water Interface,' Day et al, J. Polymer Sciences, Poly umn and that of the drying gas is dependent on the mer Letters, ed. vol. 16, p. 205 (1978); and U.S. Pat. No. volatiles which have to be evaporated from the filament 3,923,622 issued to Baughman et al. during its passage through the spinning column. In wet Polydiacetylenes exhibit fully conjugated backbones 25 spinning, the spinning dope is extruded into a spin bath with a potentially unlimited variety of side chain substit where coagulation of the spinning solution and the uents. The polymer can be depicted as follows: formation of the fiber occurs. A variety of suitable sol vent-nonsolvent systems are known in the fiber art for R use as the coagulating medium or spin bath. Suitable / 30 spin baths are nonsolvents for the polymers contained in --C the spinning blend and do not chemically react with the Y CEC spinning solution. The fiber which is formed is typically / washed to remove any adhering traces of the spin bath, R and then dried. 35 In most cases, the solvent diluent which is employed Unfortunately, polydiacetylenes are not normally provides the spinning composition (i.e., a spinning readily soluble in conventional solvents, although solu dope) with a room temperature viscosity range between ble polydiacetylenes have been made from elaborate about 0.1-3,000 poises, and preferably between about derivatives of the diacetylene monomer. In accordance 100-1,000 poises. with the present invention, it is necessary that the diace Any useful solvent can be employed. Nonlimiting tylene polymer be soluble for the carboralation reaction solvents include those for use with a water-miscible and, thus, polydiacetylenes which can be readily soluble polymer and which include water and/or water-misci in conventional solvents are the most useful. ble solvent such as methanol, ethanol, acetic acid, di It has been found that readily soluble polydiacety methylformamide, tetrahydrofuran, and the like. Sol lenes can be formed by heating diacetylene-diols in 45 vents which can be used with an oil-soluble polymer solvents with boiling points greater than 150 C. The include organic solvents such as benzene, hexane, di starting diacetylene diols can be represented by the chloroethylene, dichloroethylene, dimethylacetamide, structural formula R1O-R-C=C-C=C-R-OR dibutylether, ethylacetate, and the like. wherein R is an alkylene group of 1 to 10 carbon atoms If polymer blends are to be spun, the boron-contain and the two R1 groups may be the same or different and 50 ing polymers must be soluble in the solvents used to can be selected from hydrogen, alkyl, aryl, acyl, or silyl. dissolve the precarbonaceous polymer and form the Useful solvents include aromatic solvents such as tolu spinning dope or at least be soluble in solvents compati ene, xylene, mesitylene, prehnitrene; chloroaromatic ble with the precarbonaceous polymer solvents. It is solvents such as chloronaphthalene; polyethers such as preferred that the solvent for the boron-containing pol diglyme triglyme, etc. Reaction time must be such as to 55 ymer be the same as the solvent used to dissolve the strike a balance between the desire to bring about a precarbonaceous polymer. It is not absolutely necessary significant degree of polymerization of the diacetylene that the solvent for the boron-containing polymer and monomer and the need to readily dissolve the polymer the precarbonaceous polymer be the same as long as the for carboralation. Preferably, heating from about five to solvents are compatible. Compatibility as stated herein 150 hours at temperatures of from 150° C. to 350° C. means the solvents will form a homogenous mixture. yields polydiacetylenes of relatively low molecular The concentrations of the polymeric materials in the weight, e.g., Mw of 1,000-10,000, and which are readily spinning solution can vary widely and will depend for soluble in the refluxing solvents for the carbonalation one on the particular spinning process, e.g., dry or wet reaction. Of course, suitable reaction pressure will be which is used to form the fibers. The concentration of needed to maintain a liquid reaction medium. Carbora 65 the boron-containing polymer is the controlling factor lation proceeds as above described to yield organobo in solubility and, thus, for greater amounts of boron ron polmers having repeating carborane and vinyl containing polymer required, the solution will have to groups along the backbone thereof. be less concentrated. Typically, for wet spinning, con 4,946,919 11 12 centrations of the polymeric materials between about 5 Alternatively, the preceramic fibers can be subjected and 20% by weight will be used whereas for dry spin to a chemical stabilization treatment before being sub ning, concentrations of up to about 80% are useful. It is jected to the pyrolysis step. In a typical stabilization extremely difficult to obtain boron-containing polymer procedure, the dried fibers are contacted with a reactive concentrations near 80% and, thus, for dry spinning, a free radical-forming agent such as diazidoformanide, much higher level of the precarbonaceous polymer which effects the desired crosslinked structure in the relative to the boron-containing polymer must be uti fiber substrate at ambient temperatures (e.g., 10-40 lized. In such instance, the boron content of the formed C.). fibers will be relatively low and, thus, dry spinning is In the subsequent pyrolysis step of the process, the not a preferred method of forming boron carbide-fibers 10 wherein the amount of boron relative to carbon must proceramic fiber (either charred or uncharred) is sub approach 3:1. On the other hand, the dry spinning pro jected to a temperture between about 700–2,500 C. cess may be useful informing boron nitride, boron phos (preferably about 1,100-1,800 C.). The pyrolysis per phide or boron metalloid ceramic fibers inasmuch as the iod normally will range between about 0.2-8 hours. amount of boron-containing polymer needed is the min 15 Any pyrolysis gas can be utilized to pyrolyze the fibers. imum to form an intact fiber. High levels of the precar Thus, inert gases will lead to the formation of metal bonaceous polymer do not adversely effect the non-car carbides while reactive gases including ammonia, phos bide ceramic products since the polymer is burned away phine, and metalloid-containing gases such as metal and is not present as a carbon source. The amount of the hydrides including germane, arsine, stibine, silane, etc. precarbonaceous polymer therefore need not be con 20 will lead to boron nitride, boron phosphides, and boron trolled as in the case of the boron carbide fibers. Prefer metallic ceramics, respectively. Thus, if a carbide is ably, wet spinning is used to form the fibers since the desired, the pyrolyzation gas will be inert and the pre greater amounts of solvent allow the use of a greater carbonaceous polymer will be one that does not easily amount of organoboron polymer. burn away so as to form a carbon structure which can After a newly formed fiber is spun, it can be stretched 25 be used for reaction. On the other hand, if the ceramic or drawn to about 100-300% of its original length by alloy is to be formed from reaction of the boron poly conventional techniques. mer and the pyrolyzing atmosphere, it may be desirable The preceramic polymeric fiber can be converted to to use as the blended precarbonaceous polymer one any one of a variety of fibrous configurations prior to which burns off relatively easy. undergoing thermal treatment. For example, the fiber 30 can be in the form of filaments, staple fibers, tows, plied EXAMPLE I yarns, knits, braids, fabrics, or other fibrous assemblages This example describes the preparation of 4,5-car while undergoing thermal treatment. Alternatively var boranyl-2,3-hexyne-1,6-diol. 2,4-hexadiyne-1,6-diol pur ious fibrous configurations may be formed form the chased from Farchan Chemical was acetylated by con inorganic fibers at the conclusion of the pyrolysis step 35 ventional methods. The hexadiyne-diacetate (5.00 g, of the process. 25.75 mmol) and a slight excess of bis(acetonitrile) com To provide a final ceramic fiber product with optimal plex of decaborane (6.251 g, 30.9 mmol) were combined physical properties, it is preferred to subject the prece with 100 ml of toluene and refluxed for 16 hours. Dur ramic polymeric fiber from the preceramic fiber forma ing that time approximately one equivalent of H2 tion step to an initial thermal treatment in a molecular evolved and a very small amount a red-brown residue oxygen environment. The polymers in the preceramic was encrusted inside of the flask. The filtrate was sepa fiber are partially carbonized to a stabilized form so that rated and stirpped of solvent leaving a tacky orange the subsequent pyrolysis step of the process can be gum. The orange gum was redissolved in 250 ml of effected without the concomitant destruction of the methanol and while being iced, hydrogen chloride was fibrous configuration. The thermal treatment step can 45 be conducted by heating the fiber in a molecular oxy bubbled therethrough for 15 minutes. After reflux over gen-containing atmosphere at a temperature ranging night, the methanol was stripped and the remaining between about 200-600' C. The thermal treatment red-orange paste was smeared on a Bichner filter and temperature selected is dependent upon the polymer air-dried. The cake was redissolved in ethanol, concen resistance to distortion at elevated temperatures, and 50 trated and cooled. The carborane-diol precipitated should not exceed the polymer melting point during at when water was added to the ethanol syrup. The prod least the initial phase of the thermal treatment. uct was dried under vacuum overnight and had a melt Volatile components that evolve during the thermal ing point of 148 C. treatment step include water vapor and oxygen, and EXAMPLE II carbon monoxide and carbon dioxide resulting from a 55 partial combustion of the polymers. Typically a This example illustrates the preparation of a polyester 15-50% reduction in the weight of the fiber occurs utilizing the carboranyl-diol formed in Example I. The during the thermal treatment step. It is believed that a carboralated diol (3.0 g, 13.141 mmol) was susperided in crosslinking of carbon atoms occurs during the thermal 1 ml of toluene. When 3.5 ml of triethylamine (25 mmol) treatment to produce a charred structure. was added, the solid diol completely dissolved. Tereph The thermal treatment can be performed in an auto thaloylchloride (2.668 g, 13.141 mmol) was added and clave by heating to the required temperature/time the mix was then set to reflux for 1 day. After cooling, schedule. A continuous thermal treatment can be ac the toluene was stripped from the golden-tan solid. The complished by the continuous passage of a fiber solid was redissolved in ethyl acetate and washed with through a heated chamber or calcining furnace. The 65 5% ammonium hydroxide, water, and brine, and dried fibrous structure of the fiber is retained throughout the over magnesium sulfate. After filtrtion, the solvent was thermal treatment step. There is a tendency for the fiber removed and the solid was dried under vacuum. The to shrink while undergoing thermal treatment. solid has a melting temperatue of 95 C. 4,946,919 13 14 2. The preceramic polymer of claim 1 comprising a EXAMPLE III polyester formed by the condensation of a carboranyl This example illustrates the preparation of a polyd hexyne-diol with a dicarboxylic acid. iacetylene, poly (1,2-trans(diacetoxymethyl)-3,4-car 3. The preceramic polymer of claim 1 wherein said boranyl-1-butene). 2,4-hexadiyne-1,6-diacetate (17.8 g., carboranyl group and said acetylenic bond are conju gated relative to one another. 91.7 mmol) was refluxed for four days in 100 ml toluene 4. An organoboron preceramic polymer comprising after which the solution turned deep red. The toluene carboralated polydiacetylene. was removed and the poly(diacetylene) was left as an 5. The preceramic polymer of claim 4 comprising intensely red oil. The oil was redissolved in 100 ml 10 poly(1,2-trans(diacetyloxymethyl)-3,4-carboranyl-l-2 acetonitrile. Decaborane (5.6g, 45.9 mmol) was added butene). to the redissolved oil and the mix was set to reflux for 6. The preceramic polymer of claim 4 comprising two days. During this time, approximately 2 equivalents poly(1,2-trans(diol-methyl)-3,4-carboranyl-l-2 butene). of H2 evolved and the solution became red-brown. 7. The preceramic polymer of claim 4, wherein said After removing the acetonitrile, a tacky red-brown 15 carboralated polydiacetylene has a molecular weight solid was left. This tacky solid was dramatically cleaned (Mw) of 100 to 10,000. by diethylether. The ether leached out the brown color 8. A process for producing a readily soluble polyd from the solid which was left tan and flaky with a dull iacetylene comprising heating a diacetylene-diol having bronze luster. After separating off the ether wash and the formula R1O-R-C=C-C=C-R-OR drawing under vacuum, the solid was a light tan, very 20 wherein R is an alkylene group of 1 to 10 carbon atoms fine powder. The powder was very soluble in acetone, and R1 is the same or different and can be selected from insoluble in water and decomposed at greater than 250 hydrogen, alkyl, aryl, acyl, or silyl, in a solvent having C. a boiling point greater than 150 C. for a sufficient time The carboralated polydiacetylene was pyrolyzed by to polymerize said diacetylene-diol. heating to 200 C. at a rate of 6' C. per minute and held 25 9. The process of claim 8, wherein said heating is conducted for about 5 to 150 hours at temperatures of for one hour. The temperature was raised to 1100' C. at from 150° C. to 350° C. and at pressures sufficient to a rate of 5 C. per minute and held for two hours before maintain a liquid reaction medium. cooling overnight. Elemental analysis of the pyrolyzed 10. The process of claim 8, wherein said solvents are product showed ceramic yields of approximately 60% 30 selected from the group consisting of aromatic solvents, with boron content greater than 40%. chloroaromatic solvents, and polyethers. What is claimed is: 11. The process of claim 10, wherein said aromatic 1. An organoboron preceramic polymer having a solvents are selected from the group consisting of tolu backbone comprised of repeating units having at least ene, xylene, mesitylene, and prehnitrene. one carborane group and an acetylenic bond contained 35 12. The process of claim 8, wherein R1 is acetoxy. in the backbone of said polymer. k sk

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