(alpha, omega)phenylethynyl siloxane monomers, oligomers, and polymers

Abstract

Novel acetylene-terminated silicone monomers with (a) silane (Si--H) functionalities, (b) silanol (Si--OH) functionalities, or (c) (alpha,omega)phenylethynyl terminated siloxanes, and a novel synthetic route. The (alpha,omega)phenylethynyl-terminated siloxane monomers are prepared, starting with 1,3-bromobenzene, which is converted to 3-TMS-ethynylbromobenzene, where TMS represents the trimethylsilyl group, by reacting 1,3-dibromobenzene with trimethylsilylacetylene and triethylamine in the presence of a palladium catalyst. The 3-bromo-TMS protected phenyl acetylene is then reacted with an alkyllithium compound, such as n-butyllithium, or with magnesium to form the corresponding lithio or Grignard compound, respectively, followed by reaction with a halogenated compound, such as chlorodimethylsilane, to form 3-trimethylsilyl-ethynylphenyldimethyl silane. Next, the TMS protected ethynylphenyl silane is subjected to deprotection and methanolysis of the Si--H bond to form 3-ethynylphenyldimethyl methoxy silane, employing methanol. This silane is then hydrolyzed to form the corresponding silanol. Finally, the silanol is then condensed by known methods to form the disiloxane. The disiloxane monomer can be reacted with a cyclic siloxane, having .gtoreq.3 silicon atoms, each independently substituted with hydrogen, C.sub.1 to C.sub.6 alkyl, phenyl, or phenyl substituted with one or more alkyl or halogen groups, to form oligomers. Both monomers and oligomers form thermoset polymers by heating to a temperature of at least about 250.degree. C.