Crystal structure and thin film morphology of BBL ladder polymer

Crystal structure and morphology of poly[7-oxo-7H-benzyl(d,e)imidazo(4′,5′:5,6)-benzimidazo(2,1-a)isoquinoline-3,4:10,11-tetrayl)-10-carbonyl] (BBL) ladder-like polymer were studied. The polymer forms a two-dimensional lattice of nematic liquid crystalline structure. An orthorhombic unit cell with cell parameters of a = 7.87 b = 3.37 c = 11.97 Å was determined from the fiber diffraction pattern. In this films, the rigid chains spontaneously form a layered structure across the film thickness, but in a very unusual manner, i.e. the very large molecular plane is standing perpendicularly to the film surface plane. The results are identical to our recent results of poly (p-phenylene benzobisthiazole) (PBT) film[7]. The polymer, however, lost its anisotropic order upon extrusion into a film and resulted in a fiber-like structure.