Synthesis of novel fluorinated bis(biphenyl)diacetylene derivatives as highly birefringent nematic liquid crystalline materials

Abstract

Three novel fluorinated bis(biphenyl)diacetylene (1,4-bis(biphenyl-4-yl)buta-1,3-diyne) derivatives, with alkoxy tails at the terminal positions, were prepared for use as high-birefringent nematic materials. To lower the thermal transition temperatures and determine the origin of the nematic phase of these compounds, fluorine atoms were introduced at lateral positions. Thermal transition temperatures and mesomorphic properties were investigated by differential scanning calorimetry and polarized optical microscopy. In addition, birefringence was measured using a microscopic method based on the interference method. Both the nematogenic properties and optical performances depended not only on the number of fluorine substituents, but also on the position of the substituents. The compound having the highest fluorine content exhibited the lowest birefringence, and the compound bearing fluorine atoms only on the inner benzene rings of the biphenyl cores exhibited an enantiotropic nematic phase with a maximum birefringence value of 0.48 at 550 nm and 140 C.

One-pot synthesis and characterization of polyynes end-capped by biphenyl groups (α,ω-biphenylpolyynes)

“…In order to recognize the first member of the homologous series of α,ω-biphenylpolyynes, 1,4bis(biphenyl)-butadiyne (φ-φ-C≡C-C≡C-φ-φ) was synthesized by direct coupling reaction of ethynylbiphenyl under the Eglington conditions [52]. Ethynylbiphenyl (96 mg) was dissolved in 40 ml of ethanol and treated with 55 mg of CuCl and 88 mg of Cu(II) acetate.…”

“…The diphenylpolyynes were then studied by surface-enhanced Raman spectroscopy [30] and their nonlinear optical properties were determined [43]. Optical, vibrational and electronic properties of these carbon-atom wires were investigated on polyynes [44] and different diarylacetylenes molecules [45][46][47] which are known to exhibit liquid crystals properties suitable for electro-optical applications [48][49][50][51][52].…”

High birefringence bistolane liquid crystals: synthesis and properties

“…Liquid crystalline molecule having rigid bistolane core exhibits the highest birefringence values. 1,27,28 Such system consisted of double tolane unit ensures large p-electron conjugation. The main disadvantage of such structures is very high melting point.…”