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Birefringence of the ferro electric liquid crystals (FLCs): (S)-(−)-2-methylbutyl 4′-(4ʺ-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (S-MB-nB-BC) where n = 16 and 18 is determined experimentally using laser transmission technique. In this experimental technique, the light coming out from the laser source (of wavelength 633 nm) passes through the polarizer and analyzer via FLC sample under crossed position. Optical intensities transmitted from the sample fall on the phototransistor through the analyzer. Phototransistor is a photo detector in which the transmitted light from the analyzer is converted into the electric response and measured in terms of voltage. These voltage measurements are used to determine the birefringence values of the samples. Further, order parameter is also determined. The results are compared with image analysis technique values along with phase transition temperatures, which are in good agreement.

A novel method for temperature dependence of order parameter calculations at different wavelengths through birefringence measurements for ferroelectric liquid crystals (S)-(-)-2-methylbutyl 4′-(4″-n-alkanoyloxy benzoyloxy) biphenyl-4-carboxylates (where n = 16 and 18) has been proposed using image analysis and linear regression method of Kuczynski equation. Measurements are made for its liquid crystal phases (SmecticC*, SmecticA) to the isotropic phase of the sample. The birefringence values of the samples at different wavelengths are obtained from the textural analysis of liquid crystal as a function of temperature using MATLAB software.

A technique which combines image analysis and polarising optical microscope (POM) is a useful tool for the physical investigation of discotic liquid crystals, such as hexabutoxytriphenylene and hexahexyloxytriphenylene. This investigation includes the phase transitions, optical properties and order parameter as a function of temperature. Textures of discotic liquid crystals are captured as a function of temperature using POM. These microscopic textures are analysed using MATLAB software to compute statistical parameters, Legendre moments, optical parameters and order parameters of discotic liquid crystal samples. Compared with other techniques in the literature, the proposed methodology is a reliable and very simple technique for the physical investigation of liquid crystals.

An image analysis technique in conjunction with polarising optical microscopy (POM) is proposed for assessment of the thermo-optical properties of homogeneously aligned chiral ester liquid crystals of the type ((S)-(-)-2-methylbutyl 4′-(4″-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates, where n = 16 or 18. Chiral ester textures are recorded as a function of temperature using POM provided with a hot-stage and a high-resolution colour camera. Temperature-dependent optical parameters, or thermo-optical properties such as optical transmission, degree of polarisation, absorption coefficient and birefringence are computed for chiral esters by analysing the texture of samples using MATLAB software. This is a simple experimental technique for observing how the optical parameters of liquid crystals change with temperature.

A novel approach is proposed to investigate the phase transitions of cholesteric liquid crystals using the Legendre moments. The textures of cholesteric liquid crystals (cholesteryl butyrate, cholesteryl n-valerate, cholesteryl decanoate, and cholesteryl myristate) are captured as a function of temperature using high-resolution camera attached to the arthroscopic mode of polarizing optical microscope with hot stage. A recurrence formula is used to compute the Legendre moments of the liquid crystal textures based on the Legendre polynomial using MATLAB software. The abrupt change in the values of Legendre moments as a function of temperature gives the phase transitions of liquid crystals. The investigated transition temperatures of cholesteric liquid crystals are compared with other techniques.

Analysis of the textures and phase transitions of thermotropic liquid crystals p-ethoxybenzylidene-p-n-butylaniline, cholesteryl myristate and cholesteryl decanoate was carried out using a polarising optical microscope under crossed polarisers attached with a hot stage and a high-resolution camera. Using MATLAB software, the statistical parameters, such as mean, standard deviation, root mean square, contrast and entropy of the textures as a function of temperature, are computed. These results show abrupt changes as a function of temperature, indicating the phase transition of the sample. The statistical image analysis of various liquid crystal samples are in good agreement with the literature results and the proposed methodology offers a reliable and very sensitive technique to identify mesophase transition temperatures.

Polarizing optical microscope with a hot stage and high-resolution camera was used to record the textures of 4-Cyano-4′-pentylbiphenyl (5CB) and p-ethoxybenzylidene-p-n-butylaniline (EBBA) liquid crystals. The homogeneity histogram method was used to analyse the textures of liquid crystals by considering local and global image information. An efficient peak detection algorithm was employed to identify the most significant peaks of the homogeneity histogram. This method is useful to identify uniform regions and detect defects in liquid crystal textures.

The refractive indices of p(p-ethoxyphenylazo) phenyl (EPAP) alkanoates, which are the nematic liquid crystals where the alkyl chain n is 5, 6, 7 and 11, were measured as a function of temperature at λ = 6328 A using a wedge technique. The temperature variation of the orientational order parameter (S) is calculated at this wavelength using the Vuks model (with consideration of internal field) and by different methods excluding the internal field – Haller and Kuczynski models, and involving effective geometry parameter (αg). The intensity of light deflection in a uniaxial EPAP alkanoate with a particular molecular configuration and ordering by varying temperature is discussed. The temperature gradients of the ordinary (∂no /∂T) and extraordinary (∂ne /∂T) refractive indices are analysed. Due to a high clearing temperature with low molecular chain length, EPAP valerate exhibited low deviation of light with a large positive value of ∂no /∂T.

Phase transition temperatures of ferroelectric liquid crystals ((S)-(-)-2-methylbutyl 4′-(4″-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (where n=16 and 18)) are studied through two techniques of image analysis. One is a statistical method, applied to compute the statistical parameters from the textures of each sample and the other, computation of Legendre moments being applied as image moment analysis, both of which are considered as a function of temperature. The textures of the samples are recorded with the polarizing optical microscope (POM) attached to the hot stage and high resolution camera. The phase transition temperatures of samples are inferred by the abrupt changes in the computed parameter values. The results obtained from the present methodology are in good agreement with those published in earlier literature done by the different techniques, like differential scanning calorimetry (DSC).