Substituted rod-like aromatic polyamides: Synthesis and structure-property relations

The synthesis and structure‐property relations of a number of novel substituted paralinked aromatic homopolyamides and copolyamides are described. The synthesis of the polyamides was carried out by polycondensation of activated N,N'‐bis‐(trimethylsilyl) substitued aromatic diamines and aromatic diacid chlorides. In order to improve the solubility and to lower melting temperatures, novel arylsubstituted terephthalic acids moieties, such as p‐terphenyl‐2,5‐dicarboxylic acid and o‐terphenyl‐2,5‐dicarboxylic acid, were used in combination with substituted and noncoplanar diamines. Depending on the chemical structure, polyamides with very high solubility (up to 40% w/w) in polar aprotic solvents such as N,N‐dimethylacetamide without the addition of inorganic salts were obtained. Lyotropic liquid crystalline behavior was observed for the first time in polyamides which contain noncoplanar biphenylene units.