Structure of the Short Range Ordered Nematic Phases of nBABA (n = 1 to 9

Abstract

X-ray diffraction measurements have been carried out on the nematic phase of nBABA (n = 1 to 9). Our results show that this nematic phase is a fibre type one having in addition to the orientational long range order, two types of short range orders, (SROs): (i) one dimensional correlations of the molecular dimers along the nematic director (ň) and (ii) S_c type SRO. The strength of 1-d correlation increases with increasing n for 1 < n ≥ 3 and decreases for n > 6. The n-dependence of the length of the correlated units shows that the chains are disordered for large n The S_c type order which is length (ξ₂) is found to be asymmetric with ξ_2∥(∥ṋ) > ξ₂⊥ (⊥ṋ). This asymmetry decreases with increasing n The formation of the observed structures in the SROs has been qualitatively explained taking into account various types of intermolecular interactions.

Key Words:

• liquid crystals
• nematics
• short range order
• X-ray diffraction