A new mesogenic monomer was prepared from biphenyl-3,3',4,4' -tetracarboxylic dianhydride and 4-aminophenol followed by the acylation of OH groups with propionic anhydride. This diphenol propionate was polycondensed by transesterification with decane-1,10-dicarboxylic acid, dodecane-1,12-dicarboxylic acid, and eicosane-1,20-dicarboxylic acid or with equimolar mixtures of two dicarboxylic acids. The resulting poly(ester imide)s were characterized by elemental analyses, H-1 NMR spectra, inherent viscosities, DSC measurements, optical microscopy, and X-ray measurements with synchrotron radiation at variable temperatures. An enantiotropic smectic A phase in the molten state and a crystalline smectic E (or H) phase in the solid state were found in all cases.