MESOMORPHISM IN SEGMENTED-CHAIN POLYMERS CONTAINING FLEXIBLE SUBSTITUENTS IN THE RIGID MOIETY

The synthesis and the phase behavior of a set of polymers characterized by having moderate chain flexibility and highly flexible lateral substituents are reported. The polymers have general formula (-p-C6H4-OOC-p-C6H3(R)-COO-p-C6H4-O(CH2)(n)O-)(x) with R = -O(CH2)(m-1)CH3 (m = 5-8) and n = 2, 4. The presence of the lateral substituents, together with some chain flexibility, leads to comparatively low melting temperatures (lower than similar to 190 degrees C, for annealed samples) allowing a nematic liquid-crystalline behavior to show up in a thermotropic, enantiotropic way. X-ray diffraction data collected for annealed fibrous samples at room temperature indicate that the structural periodicity along the fiber axis substantially corresponds to the length of the monomer unit in its most extended conformation. The same holds for fibers not annealed. In;this case, however, the regularity of the chain packing both along and across the fiber axis is drastically disturbed such that the solid state should better be classified as a mesophase.