Synthesis and properties of para‐linked aromatic polyesters containing 2,2′‐dimethylbiphenylylene units

The syntheses and properties of a series of para‐linked aromatic homopolyesters with 2,2′‐dimethylbiphenylylene units are described. In the 2,2′‐dimethyl‐substituted biphenylylene unit the phenyl rings are forced into a non‐coplanar conformation, which decreases the interchain interactions. The combination of such a biphenylylene unit with a monosubstituted unit further reduces the regularity of the substituents along the polyester backbone. As a result, soluble and completely amorphous liquid‐crystalline (LC) aromatic polyesters with low phase transition temperatures are obtainable. Ternary solutions, consisting of a soluble aromatic LC polyester, a conventional randomly coiled thermoplastic and chloroform as solvent, can be used for the preparation of films and fibers.