The present invention relates to a polyorganoborosilane ceramic precursor polymer comprising a plurality of repeating units of the formula: ##STR1## with the segments being linked together by second units of the formula: --(R.sup.2)--Si--R.sup.3)--q, where R.sup.1 is lower alkyl, cycloalkyl, phenyl, or ##STR2## and R.sup.2 and R.sup.3 are each independently selected from hydrogen, lower alkyl, vinyl, cycloalkyl, or aryl, n is an integer between 1 and 100; p is an integer between 1 and 100; and q is an integer between 1 and 100. These materials are prepared by combining an organoborohalide of the formula R.sup.4 -B-(X. sup.1).sub. 2 where R.sup.4 is selected from halogen, lower alkyl, cycloalkyl, or aryl, and an organohalosilane of the formula : R.sup.2 (R. sup.3) Si(X.sup. 2).sub.2 where R.sup.2 and R.sup.3 are each independently selected from lower alkyl, cycloalkyl, or aryl, and X.sup.1 and X.sup.2 are each independently selected from halogen, in an anhydrous aprotic solvent having a boiling point at ambient pressure of not greater than 160° C. with in excess of four equivalents of an alkali metal, heating the reaction mixture and recovering the polyorganoborosilane. These silicon boron polymers are useful to generate high-temperature ceramic materials, such as SiC, SiB.sub.4, and B.sub.4 C, upon thermal degradation above 600. degree. C.
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