Maximizing the formation of low-melting, mesogenic oligomers from the catalytic polymerization of pyrene

Abstract

Abstract Experimental data has been measured for the catalytic polymerization of pyrene and used to generate a microkinetic reaction model capable of predicting reaction conditions suitable for producing low-melting mesophases. Although pyrene trimer forms 100% mesophase with a low melting point, product yield as a percentage of the feed pyrene monomer is low. Thus, the strategy is to produce a mesogenic material consisting of three pyrene oligomers: dimer, trimer, and “x-mer” (i.e., tetramer and higher oligomers). Using the microkinetic model, a wide range of operating conditions has been explored; two scenarios are worth experimental investigation to determine the extent of mesophase formation in the proposed oligomeric mixtures: (1) moderate reaction temperatures and short reaction times, which minimize the formation of high-melting x-mer and (2) moderate temperatures and long reaction times, which eliminate the need for monomer and dimer stripping to build up the molecular weight of the pyrene pitch product. Finally, NMR measurements of the pyrene pitch products indicate that the oligomers are completely cyclized, with oligomers consisting of monomer units connected by single C–C bonds being undetectable. With complete cyclization occurring, one would expect better mechanical properties in carbon products (e.g., carbon fibers) made from such a mesophase pitch.