N,O-Bistrimethylsilyl-4-aminobenzoic acid was selectively acylated at the amino group with 4-acetoxy-3-methoxybenzoyl chloride. The resulting dimer with silylated carboxyl group was polycondensed in situ at 300 or 350 degrees C using Marlotherm-S as an inert reaction medium. In an alternative approach the silylester group of the dimer was hydrolysed and the resulting N-(4’-acetoxy-3-methoxybenzoyl)-4-aminobenzoic acid was polycondensed at 300 or 350 degrees C. Furthermore, copolyesters rich in vanillic acid units were prepared by co-condensations with 4-acetoxy-3-methoxybenzoic acid or its trimethylsilylester. Elemental analyses and H-1 nuclear magnetic resonance spectra indicate that the vanillic acid units partially decompose at 350 degrees C, whereas at 300 degrees C the composition of the copolyesters agrees well with the feed ratio. Infra-red spectra support this conclusion. Wide-angle X-ray diffraction powder patterns indicate that the crystallinity increases with higher molar fractions of vanillic acid. The 1:1 copolymers are nearly amorphous. The copoly(ester-amide)s obtained from the monomers with free carboxyl groups form globular aggregates regardless of composition. In contrast, the silylated monomers yield columnar particles with lengths of 10-15 mu m and aspect ratios greater than or equal to 10 for copoly(ester-imide)s with a 6:4 and 5:5 composition. Transmission electron microscopy revealed ordered structures in these columnar particles, but the ’crystal growth’ cannot yet be interpreted.