Crystal structure of fibers from a novel rigid‐rod aromatic polyamide containing a pyrimidine moiety

Fibers of a novel rigid‐rod polyamide containing a 1:1 ratio of phenylene:pyrimidine moieties have been produced and evaluated. The lyotropic liquid‐crystalline behavior of the polymer and the spinnability of the nematic dope were established. The as‐spun fibers exhibit low degrees of orientation and crystallinity. Heat treatment of the dry fibers resulted in crystallinities as high as 45% in coexistence with an amorphous phase component. Evaluation of the crystal structure by wide‐angle X‐ray diffraction suggests a pseudo‐orthorhombic crystal cell with lattice dimensions (a; b; c) of (7,3 Å; 5,1 Å; 12,8 Å) and containing two repeating units per unit cell.