Structure and swelling of halogenated mesophase pitches

An attempt has been made to characterize the structure of the reaction products resulting from the halogenation of mesophase pitch. FT-i.r. spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction show the presence of halogenated aromatics and hydroaromatics which are of a lower lamellar orientation than in non-halogenated mesophase pitches. The halogenated pitches swell in contact with solvents acting as electron donors or acceptors. Basic organic solvents are the most active swelling agents. A crosslinked structural model is proposed which comprises ordered domains of lamellar aligned aromatics and a disordered network. The crosslinks are bonding regions to join the ordered domains and the disordered material. It is assumed that halogenated hydroaromatic molecules assist in producing the crosslinks.