The thermotropic liquid crystalline behavior of a mixed-substituent poly(organophosphazene) containing trifluoroethoxy and (6-(4-phenylphenoxy)hexyl)oxy side chain groups has been investigated by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. Upon cooling from the isotropic Liquid a "batonnet" texture mesophase formed, which is indicative of a smectic-like structure as compared to low molar mass molecules. The texture grows and coalesces to a final texture. The X-ray diffraction pattern of the "captured" structure upon quench-cooling from the mesophase indicated a mixture of smectic C- and A-like phases. The phosphazene backbone layer thickness is approximately 2.4 mo, and the mesogenic (6-(4-phenylphenoxy)hexyl) oxy side chain overlaps in an antiparallel, interdigitated structure within this layered interval. Mesophase formation in the mixed-substituent polyphosphazene is due largely to the chemical inhomogeneity of the side chain groups, since the single-substituent polyphosphazene containing the same biphenyl side chain does not exhibit a liquid crystalline phase.