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A series of four novel azobenzene liquid crystals (LCs) with high birefringence were synthesized by coupling of intermediate molecules with a phenylacetylene fragment. The chemical structures of synthetic intermediates and compounds were confirmed by FT-IR and1H-NMR. The LC behavior including transition temperatures and phase sequences were investigated by differential scanning calorimetry (DSC) and polarizing optical microscope (POM). As a very important parameter, the birefringence was also measured using polarizing light interferometry method. Moreover, the characteristics of selective reflection which was associated with the birefringence of the N*-LC dropped with azobenzene LCs and the effect of trans-cis photoisomerization of these compounds on selective reflection were studied in detail. [ABSTRACT FROM PUBLISHER]

When mesogenic compound with high birefringence was incorporated into a chiral nematic liquid crystal (N*-LC), the resulting composites generated higher birefringence to change the selective reflection of N*-LC. The effects of variables such as content of chiral dopant and mesogenic compound, temperature, and AC voltage on the selective reflection of N*-LC were systematically studied. [ABSTRACT FROM AUTHOR]

A series of asymmetrically disubstituted liquid crystalline compounds with high birefringence based on phenyldiacetylenes was synthesised by coupling of intermediate molecules with a phenylacetylene fragment. The structures of the intermediates and resulting compounds were confirmed by Fourier transform infrared, 1H nuclear magnetic resonance and Matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Their liquid crystalline behaviour, including transition temperatures and phase sequences, was investigated by differential scanning calorimetry and polarising optical microscopy. As an important parameter, the birefringence was also measured, using polarising light interferometry. The results indicated that the compounds exhibited different liquid crystalline phases in the high temperature region, with high birefringence values. In addition, the selective reflection characteristics associated with birefringence under conditions which maintained the matrix nematic liquid crystal and the concentration of chiral dopant were studied. [ABSTRACT FROM AUTHOR]