Carbon mesophase-substrate interactions

The formation, growth and coalescence of mesophase materials have been followed by hot stage microscopy and by room temperature examination of polished surfaces for various mesophase-forming materials and in the presence of various substrates. The appearance of mesophase particles should be preceded by polymerization of isotropic material into sheet-like molecules, followed by orientation of the sheet-like molecules into ordered regions. Precipitation, growth and coalescence should require ordering of small molecules in a viscous medium. Our results indicate that dynamic motion in the fluid, rather than the presence of nucleating particles, is the controlling factor, very likely reflecting a small mesophase-isotropic liquid interfacial energy. Where dynamic motion is restricted, as in the interstices of a yarn, mesophase formation and growth are also restricted. Alignment of mesophase material with a substrate is primarily controlled by the motion of the mesophase droplets as they flow across the substrate. In general, substrates are not wetted by mesophase in the presence of isotropic material. Certain surfaces are wetted by the mesophase droplets but alignment appears to be controlled more by flow orientation than by surface energy interaction.