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ZnO nanoparticles (nps) have wide range of applications and improve the optical parameters of molecules of soft liquid crystalline (LC) materials. The present paper mainly discusses the optical studies on LC materials regarding p-n-butyloxybenzoic acid (4oba) and p-n-butylbenzoic (4ba) compound along with homogeneous dispersion of ZnO nps in lower weight concentration, i.e., 1, 1.5, 2 and 2.5 wt%. The existence and size of ZnO nps in LC compounds are well determined through spectroscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). The temperatures of LC compounds and phase transitions are determined by using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) which is found to decrease with increasing concentration of dispersed ZnO nps. Image enhancement with visual quality matrix method is used to improve the quality of the image. Specially designed wedge-shaped modified spectrometer is used to determine the refractive indices with different wavelengths (460, 500, 570 and 635 nm). The refractive indices measured are fitted with two and three coefficient Cauchy model. Further, the order parameter S of the molecules of 4ba and 4oba with dispersed ZnO nps are determined by molecular field models namely Kuczynski, Vuks and effective geometry model, respectively. From the data, it is found that the values of birefringence (δn) and order parameter (S) of the molecules of 4oba and 4ba are enhanced with the dispersion of ZnO nps with increasing weight concentrations in the stabilized nematic thermal region.

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Citrate-capped gold nanoparticles (Gnps) have multiple applications in all optical devices and influence the properties of birefringence in liquid crystalline (LC) molecules. In the present paper, systematic studies have been carried out on LC compounds p-n-undecyloxy benzoic acid (11oba) and p-n-dodecyloxy benzoic acid (12oba) with dispersed citrate-capped Gnps in different low molar concentrations. The phase transition temperatures of the LC nanocomposites obtained from polarizing thermal microscopy (POM), differential scanning calorimetry (DSC) and modified spectrometry are found to be reduced with the increase in concentration of dispersed citrate-capped Gnps. The information was obtained from textural data utilizing the simple technique gradient measurement of standard deviation (GMSD) using the MATLAB tool, which is analogous to DSC. Further, the existence of citrate-capped Gnps in 11oba and 12oba was determined by spectroscopic techniques like ultraviolet-visible spectrometry and scanning electron microscopy. The birefringence measurements were carried out at different wavelengths (460, 500, 570 and 635 nm) using a wedge-shaped cell with a modified spectrometer. The birefringence (δn) increases with increase in weight concentration of citrate-capped Gnps in the nematic thermal range. Further, the order parameter S values obtained from the Kuczynski internal field model, the Vuks model, the Haller extrapolation model and the effective geometry parameter methods are in good agreement. It is found that the order parameter S increases with increase in dispersion of concentration of citrate-capped Gnps. This is due to strong Van der Waal’s interaction between the LC molecules and citrate-capped Gnps, which increases the alignment of the LC molecules.

The synthesis and characterisation are carried on liquid crystalline (LC) p-dodecyloxy benzoic acid (12OBA) with 1 and 2 wt% for PdCl 2 nanoparticles dispersion. Further, characterizations are carried out by different spectroscopic techniques like X-ray diffraction spectrometric studies, scanning electron microscopy, Fourier transform infrared and differential scanning calorimetry (DSC). Textural determinations of the synthesised compounds are recorded by using polarising optical microscope (POM) attached with a hot stage and camera. The results show that the dispersion of PdCl 2 nanoparticles in 12OBA exhibits Nematic phases as same as the pure 12OBA with reduced clearing temperature as expected. Further, the nematic thermal ranges are quenched and the smectic C thermal range has been increased while performing both DSC and POM with the dispersion of 1 wt% PdCl 2 nanoparticles. Size dependence on bonding nature with LC compounds is established. KEYWORDSSynthesis; polarising optical microscope (POM); differential scanning calorimeter (DSC); nano dispersion; X-ray diffraction (XRD); Fourier transform infrared (FTIR) spectroscopy; scanning electron microscopy (SEM)