MOLECULAR-ORGANIZATION OF LIGNIN DURING CARBONIZATION

Thermotropic liquid-crystalline (LC) behaviour of lignin-like model co mpounds, lignin, (commercial) petroleum pitch and blends of lignin and pitch was studied using hot-stage optical microscopy. The results ind icate that, while all the dimeric lignin-like model compounds represen ting beta-O-4, beta-5 and 5-5 intermonomer linkages exhibit thermotrop ic LC phenomena in some temperature range, the LC behaviour remains in complete for lignin. At the temperature at which a maximum amount of L C behaviour is observed for lignin, large carbonized particles are obs erved as well. This prevents the formation of a molecularly organized fluid phase from ever developing. The inability to fluidize totally at elevated temperatures is likely to be responsible for lignin's (ligni n derivative's) inability to produce high-strength, high-modulus carbo n fibres.