Formation of Smectic Spherulites in Poly(ester imides)

The formation of higher-ordered smectic-crystalline phases resulting directly from the isotropic melt is determined in different poly(ester imide)s (PEI). The microscopic extinction patterns and the results of H(v)-light scattering and time-resolved X-ray diffraction during isothermal crystallization indicate that a spherulitic superstructure is formed if no intermediate LC-phase occurs. This phase behavior is found in PEIs based on aminobenzoic acid trimellitimide and long aliphatic diols and in PEI derived from pyromellitic acid anhydride, omega-aminoundecane acid and aromatic diols, resp., which form no LC-phase at all. Additionally, this smectic-spherulitic morphology is formed by PEIs based on aminocinnamic acid trimellitimide, which pass through a monotropic LC-phase upon cooling if the polymer is crystallized at temperatures above the LC-phase. The competition between LC phase formation and spherulitic crystallization is discussed on the basis of thermodynamical and kinetical influences. The spherulites formed have a lamellar structure of 100-400 angstrom giving rise to a SAXS reflection. Whereas the crystal lamellae contain an internal smectic layer structure of about 30 angstrom, the region between the lamellae is probably amorphous.