Orientational distribution function in nematic liquid crystals by x-rays: Fourier method

The existing methods for the determination of the orientational distribution function f(beta) in the nematic liquid crystals using X-rays have been reviewed. A simple Fourier method which gives f(beta) in terms of the measured intensity is analysed. Using this distribution function, the accuracy with which the order parameters could be evaluated is discussed and the results show the elegance of the Fourier method used here

2-Methylxanthen-9-one

In the title compound, C14H10O2, the tricycle is not planar, being bent with a dihedral angle of 4.7 (1)° between the two benzene rings. In the crystal, π–π inter­actions between the six-membered rings of neighbouring mol­ecules [centroid–centroid distances = 3.580 (3) and 3.605 (3) Å] form stacks propagating along [101]

Optical Effects and Molecular Ordering in the Ringed Spherulites of Mixtures of Cholesterol and Nematic P-Anisaldazine

In this paper we discuss the results of our investigations with ringed spherulites formed in the solid phase of pure cholesterol and also in the mixture of cholesterol and nematic p-anisaldazine. The observed ringed spherulite textures are found to exhibit upto four orders of optical diffraction. Using polarizing microscope, the ring spacing d of the ringed spherulites were measured as a function of concentration of p-anisaldazine in the total weight of the mixture. The nature of the molecular order in the ringed spherulites has also been explained using two sensitive optical interference techniques. The optical birefringence measured for pure cholesterol in the solid phase varies from 0.0134 to 0.0163 as the wavelength is changed from 553 nm to 440 nm

Optical-Properties of Spherulites of Cholesteryl-Do-Decyl Carbonate

We report here some very interesting optical textures exhibited by a pure cholesterogenic compound viz., Cholesteryl-do-decyl carbonate. It also exhibits ringed spherulitic texture when crystallized at different temperatures. The observed ring spacing is found to increase with the increase of crystallization temperature and we were also able to determine Avarami's constants by studying the growth rate of these spherulites. Light scattering and optical diffraction studies have been carried out using optical textures exhibited by the sample. The local order parameters corresponding to untwisted nematic structure in the cholesteric layer has been estimated at various temperatures in the cholesteric phase using the measured refractive index and density data