title: Enantiotropic nematics from cross-like 1,2,4,5-tetrakis(4'-alkyl-4-ethynylbiphenyl)benzenes and their biaxiality studies.
abstract: The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross-shaped compound 3, which showed enantiomeric nematic phase behavior. This cross-like core structure could alternatively be viewed as two fused V-shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface-induced biaxiality was evidenced by optical studies. Cluster-size analysis within the nematic phase of compound 3 revealed the formation of meta-cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small-angle 2D X-ray diffraction patterns of magnetic-field-aligned samples indicated that the nematic phase was composed of small smectic C-like clusters with the tilting of molecules within the clusters. The wide-temperature-range enantiomeric nematic phase of cross-like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent-rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher-order liquid-crystalline phases and crystallization, for future biaxial investigations.
authors: Department of Chemistry, Tamkang University, 251 Taipei, Taiwan.
authors: Hsiu-Hui
authors: HH
authors: Chen
authors: Hsing-An
authors: HA
authors: Lin
authors: Yin-Hui
authors: YH
authors: Lai
authors: Shu-Yu
authors: SY
authors: Lin
authors: Chien-Hung
authors: CH
authors: Chiang
authors: Hsiu-Fu
authors: HF
authors: Hsu
authors: Tzenge-Lien
authors: TL
authors: Shih
authors: Jey-Jau
authors: JJ
authors: Lee
authors: Chien-Chen
authors: CC
authors: Lai
authors: Ting-Shen
authors: TS
authors: Kuo