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 hydrobor onation of acenaphthylene. The pyrolyses were performed at an argon ga s pressure of 1 MPa to suppress the evaporation of volatile products. All synthesis routes are attractive due to possible boron yields in th e range of 100%. In the co-pyrolysis route, this result is only obtain ed with pyridine-borane and not with other borane complexes like trime thylamine-borane and piperazine-borane. (C) 1998 Elsevier Science Ltd. All rights reserved.