Element-substituted polyaromatic mesophases: II a comparison of various synthesis routes for boron substitution

The synthesis of boron-substituted polyaromatic mesophase was studied by (1) co-pyrolysis of a filtered coal tar pitch with three different borane complexes, (2) pyrolysis of a boron-containing polymer produced by co-polymerisation of divinylbenzene with borane, and (3) pyrolysis of boron-substituted/crosslinked acenaphthplene, produced by hydroboronation of acenaphthylene. The pyrolyses were performed at an argon gas pressure of 1 MPa to suppress the evaporation of volatile products. All synthesis routes are attractive due to possible boron yields in the range of 100%. In the co-pyrolysis route, this result is only obtained with pyridine-borane and not with other borane complexes like trimethylamine-borane and piperazine-borane. (C) 1998 Elsevier Science Ltd. All rights reserved.