Phase characteristics for ternary systems, rodlike polymer/flexible polymer/solvent system and rodlike polymer/another rodlike polymer/solvent system, were determined by polarized optical microscopy at 30℃ and 60℃, and compared with Flory's theory. Poly(p-phenylene terephthalamide) (PPTA, Dupont Co.), M4-polymer and M6-polymer were choosen as rigid rodlike polymers. Among them, M4-polymer and M6-polymer were synthesized by Higashi reaction method. Poly(m- phenylene isophthalamide) (PMIA) was used as a flexible polymer and the single solvent is 100\% $H_2SO_4$.
Single anisotropic phase appeared in PPTA-rich regions of PPTA/PMIA/$H_2SO_4$ ternary system because of high axial ratio of PPTA. Also the possibility of the single anisotropic phase was verified through Flory's theory for $x_2=69.3$ and $x_3=10$ in rodlike polymer/flexible polymer/solvent ternary system.
On the other hand, M6/PMIA/$H_2SO_4$ system revealed no single anisotropic phase in both experiment and theory. In all the region of this system and PMIA-rich regions of PPTA/PMIA/$H_2SO_4$ system, phase separation due to the poor miscibility between two polymers was predicted and observed at the higher concentration than the critical concentration.
PPTA/M6/$H_2SO_4$ and PPTA/M4/$H_2SO_4$ ternary systems were in agreement with theory except the binodial curve for the anisotropic phase which showed an inflection point.
In general, with increasing concentration single anisotropic phases were observed at the whole volume ratios of a rodlike polymer to another rodlike polymer in rod/rod/solvent systems. Above all the metioned systems show that the addition of the third component to the binary system yields the extention of biphasic region, and that these systems are consistent with theory qualitatively but not quantitatively because of many assumptions of Flory's theory.