Molecular Structure in the Crystalline Phase of a Segmented Liquid Crystalline Polyester

Molecular structure refinement of a liquid crystalline segmented polymer using X-ray diffraction methods is reported. The investigated polymer contains the 3-allylbiphenyl unit as nematogenic unit. The space group is P21/a, with cell parameters a ) 12.82 Å, b ) 8.44 Å, c ) 19.72 Å, and â ) 153.2°, with two chains per unit cell. The main feature of this molecular packing is the layered organization of chains with a transversal intercalation of the flexible and the rigid units in the layer. Repetition of layers in space leads to an herringbone packing of biphenyl units along [001]. Transversal register between chains is such that the two phenyl rings of biphenyl unit are involved in “edge to face” contact.