Production and charecterization of 6BA/nABA (n=3, 4) liquid crystal mixtures

In this thesis, homogeneous liquid crystal mixtures were produced by mixing non-mesogenic 3-Aminobenzoic acid (3ABA) and 4-Aminobenzoic acid (4ABA) with mesogenic 4-Hexylbenzoic acid (6BA) in certain proportions. The thermal, microstructural and optical properties of the produced liquid crystal mixtures were investigated. Thermal analyzes were made using a Differential Scanning Calorimetry (DSC) device. By using DSC data, important properties such as phase transition temperature, enthalpy and activation energy in liquid crystal phases were investigated. DSC results showed Smectic and Nematic phase transition peaks, indicating liquid crystalline phases during continuous heating and cooling. It was observed that the phase transition temperature values obtained during cooling were lower than the phase transition temperature values obtained during heating. Polarized optical microscope (POM) studies were carried out to make liquid crystal phase naming. Consistent with DSC, as a result of POM analysis, smectic A, smectic C and nematic phases were detected in the produced liquid crystalline mixtures. Activation energy values were calculated for each phase transition using the phase transition peak values. FTIR analysis of the binary mixtures of 6BA/3ABA and 6BA/4ABA was performed and it was observed that hydrogen bonds were formed between the molecules of the mixture components. In addition, the crystallographic properties of the produced samples were investigated by X-ray diffraction (XRD). Basal distance values were calculated in molecular sequences using XRD results. It was observed that the basal distance values of the mixture were between the basal distance values of the components.