EFFECTS OF REDUCTIVELY INTRODUCED ALKYL-GROUPS AND HYDROGEN TO MESOPHASE PITCH ON CARBONIZATION PROPERTIES

A mesophase pitch, which consisted of developed aromatic rings (15-17 fused rings) and contained only a few alkyl groups per molecule, was subjected to reductive alkylation (methyl and ethyl) and hydrogenation using potassium metal followed by alkyl iodide and alcohol, respectively, in order to assess the effects of reductively introduced alkyl groups and hydrogens on the formation of anisotropic texture. When the hydrogenated pitch was carbonized at 400-degrees-C for 10 min, the anisotropic content increased by an increase in the number of introduced hydrogens, while the anisotropic content from the alkylated pitch decreased, depending on the number and steric size of alkyl groups introduced. The original and hydrogenated pitches were nearly stable until 400-degrees-C, whereas dealkylation occurred for the alkylated pitches. A degree of the demethylation increased by an increase in a soaking period at 400-degrees-C, accompanied by an increase in the anisotropic content. The demethylation led to no significant polycondensation reactions, and resulted in an increase in the stabilized radical concentrations. The bulkiness of the reductively methylated and hydrogenated products was calculated to be 7.6 and 5.2 angstrom by adopting dihydrodimethyl- and dihydro-pyrene as model compounds, respectively. The difference in such steric sizes between the two groups may be responsible for the different tendency in the anisotropic formation when carbonized at 400-degrees-C for 10 min.