| 초록 |
The Crystal structure of poly(2-cyano-1,4-phenylene terephthalamide)(Cy-PPDT) was studied using wide angle X-ray, winLALS refinement, FT-IR, ab-initio calculation, 13C solid NMR and molecular modeling methods. Cy-PPDT fiber spun in the liquid crystalline state and anneal at high temperature offered well-oriented X-ray pattern. A total number of 16 reflections could be resolved in X-ray fiber pattern. The observed reflections could be indexed with monoclinic(metrically orthorhombic) unit cell parameters of a=9.44Å, b=5.06Å, c=12.9Å. The systematic absence of the observed reflections was observed for hk0(h+k=odd) and h0l(l=odd) reflections. Two chains are in the unit cell and the crystal structure has the glide plane symmetry by space group of P11n. The unit cell of Cy-PPDT is similar to the poly(p-phenylene terephthalamide) (Kevlar) with dilation of a axis due to the bulky -CN groups. The torsion angle between the phenylene planes and the amide planes in Kevlar are 38° for the p-phenylene diamine segment and -30° for the terephthalic segment. In the Kevlar crystal, intermolecular hydrogen bonding between C=O and N-H along b direction but the Cy-PPDT is possible to double hydrogen bonding according to the position of substituted -CN groups. The torsion angle in the p-phenylene diamine segment changed from -38° to -50° by substitution of the CN groups in phenylene ring. The crystal structure of Cy-PPDT was refined using winLALS and X-ray fiber diffraction patterns were also simulated using Cerius2 software. The simulated X-ray pattern is well matched with the observed X-ray pattern. |
