CRYSTAL-STRUCTURES OF POLY-PARAPHENYLENE OLIGOMERS CONTAINING PENDANT PHENYL GROUPS

The room temperature crystal structures of 1,2,4-triphenylbenzene (TPB), C24H18; 22,45-diphenyl-p-quinquephenyl (DPQ), C42H30; and 22,65-diphenyl-p-septiphenyl (DPS), C54H38, have been investigated as part of a research programme in rigid-rod polymers, materials which are of great interest for aerospace and electro-optical applications. The molecules are non-planar, in contrast to the planar structures found at room temperature for the unsubstituted polyphenyls. The oligomer axis does not align with any of the crystallographic axes. The pendant-oligomer bond, however, does align with the longest crystallographic axis. The pendant torsion angle is greater than 45° and increases with increasing chain length. Knowledge of molecular structure and crystal packing of oligomeric model compounds will be useful in further calculations of mechanical, optical, and electro-optical properties for the corresponding rigid-rod polymer structures. © 1990.