| 초록 |
The crystal structures of poly(1,5-naphthalene-benzobisthiazole) (Naph-1,5-PBT) and poly(2,6-naphthalene-benzobisthiazole) (Naph-2,6-PBT) were studied using X-ray and molecular modeling methods. The X-ray fiber pattern of Naph-2,6-PBT is similar to that of poly(p-phenylene-benzobisthiazole) (PBT) having streaks along the layer lines, indicative of axial disorders in the crystal while that of Naph-1,5-PBT is typical of the well-developed crystal structure. The crystal structure of Naph-1,5-PBT has the monoclinic unit cell with dimensions of a=7.34Å, b=3.70Å, c=12.7Å, β=115º in which adjacent chains are staggered by c/4 in the ac plane and naphthalene ring is twisted along the chain backbones by torsional angle of 138°, which was derived from ab-initio energy calculations as well as from the comparison of intensities of reflections. The crystal structure of Naph-2,6-PBT has the monoclinic unit cell with dimensions of a=6.68Å, b=3.45Å, c=14.7Å and β=113.2º in which adjacent chains are staggered in the ac plane by c/5 and in the bc plane by ±c/2 (+,- directions are random) causing axial disorders in the crystal. The perfect crystal structure of Naph-1,5-PBT compared to that of Naph-2,6-PBT may be due to the zig-zagged shape of the chemical structure as well as the twisted structure arising from the steric interaction between the large sulfur atom of the heterocycle and α-hydrogen of naphthalene ring of Naph-1,5-PBT. The zig-zagged shape and twisted structure of Naph-1,5-PBT makes it difficult to shift randomly along the axial direction. |
