Structure of the Short Range Ordered Nematic Phases of nBABA (<i>n</i>= 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) Sc 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 Sc type order which is length (ξ2) is found to be asymmetric with ξ2∥(∥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.

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