Chemistry Letters, Vol.32, No.2, 168-169, 2003
Microvoids present in anisotropic mesophase pitch, their as-spun and annealed fibers
The sizes of free volumes in the mesophase pitches, as-spun and annealed fibers were measured by positron annihilation lifetime spectroscopy (PALS). The size of free volume increased with increasing of methyl groups in the mesogen molecules. Spinning increased the free volume while annealing after the spinning decreased it to similar value of the starting pitch.