METAL-CATALYZED ALKYNYLATION OF BROMINATED POLYPHENYLENES - THERMOSET PRECURSORS OF HIGH-DENSITY MONOLITHIC GLASSY-CARBON

The functionalization of brominated polyphenylenes with several alkynes is described. The bromide groups on the polymer were replaced with terminal alkynes using a Pd/Cu catalyst system. Substitution of nearly all the original bromide locations was achieved. The functionalized polymers, freely soluble in THF, exhibited high char yields of up to 89 % on thermolysis to 900-degrees-C under a nitrogen atmosphere. Several of the functionalized polymers, derived from brominated polyphenylenes with approximately equal amounts of meta and para linkages, flowed on heating. The polymer that was functionalized with phenylacetylene exhibited a well-defined melting point at approximately 200-degrees-C and flowed to produce a monolithic disk of glassy carbon. The amount of acetylenic cross-linking units in the polymers functionalized with phenylacetylene appears to be directly related to the char yields of the functionalized polymers. Predominantly meta-linked brominated polyphenylenes were also functionalized with a number of terminal alkynes, and though high char yields of up to 86 % were observed, these materials offered no improvements in flow properties. The structure/property relationships and material applications are discussed.