Thermotropic liquid-crystalline (LC) behaviour of lignin-like model compounds, lignin, (commercial) petroleum pitch and blends of lignin and pitch was studied using hot-stage optical microscopy. The results indicate that, while all the dimeric lignin-like model compounds representing fl-O-4, #-5 and 5-5 intermonomer linkages exhibit thermotropic LC phenomena in some temperature range, the LC behaviour remains incomplete for lignin. At the temperature at which a maximum amount of LC behaviour is observed for lignin, large carbonized particles are observed 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 (lignin derivative's) inability to produce high-strength, high-modulus carbon fibres.
Посилання на статтю:
Molecular organization of lignin during carbonization / Vipul Dave*, Abaneshwar Prasadt, Herv6 Marandt and Wolfgang G.Glasser*: // Polymer. – 1993. – Vol 34. – P. 3144-3154.