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

The synthesis and the phase behavior of a set of polymers characterize d by having moderate chain flexibility and highly flexible lateral sub stituents 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 wi th some chain flexibility, leads to comparatively low melting temperat ures (lower than similar to 190 degrees C, for annealed samples) allow ing a nematic liquid-crystalline behavior to show up in a thermotropic , enantiotropic way. X-ray diffraction data collected for annealed fib rous samples at room temperature indicate that the structural periodic ity along the fiber axis substantially corresponds to the length of th e monomer unit in its most extended conformation. The same holds for f ibers 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.