Quantitative analysis on carbonaceous mesophase from fused-state 13C NMR spectra – Molecular structure, orientation and fluctuations of the constituents

Abstract

A new 13 C NMR measurement technique, named fused-state 13 C NMR, has been developed. Using this technique, many aspects of carbonaceous mesophase have been elucidated: constituents of soft mesophase have methyl and/or naphthenic groups whereas those of hard mesophase have no aliphatic groups. The order parameter of carbonaceous mesophase in the nematic phase is about 0.7. Very small molecules such as hexamethylbenzene and pyrene orientate in a carbonaceous mesophase. In a liquid crystalline phase, all oriented molecules in a carbonaceous mesophase (including the small molecules trapped in the mesophase) fluctuate around the orientation axis in the same manner. That is, an oriented molecule behaves as if it were trapped between two walls the distance between which is about 1.0 nm. The analyzed results rule out the assertion that soft mesophase is a gel and also rule out the existence of basic structural units. A constructed model for molecular ordering in a mesophase has clarified some pending questions on carbonaceous mesophase. [TANSO 2012 (No. 254) 187–204.]