The long-range orientational order of liquid crystals from homologous series of 4-n-alkyl-4 -cyanobiphenyl, 4-n-alkoxy-4 -cyanobiphenyl, trans-4-n-alkyl(4 -cyano-phenyl)-hexane, and 4-(trans-4 -n-alkylcyclohexyl)--isothiocyanato-benzene was studied by means of classical methods of optical spectroscopy: absorption of the polarized light, fluorescence depolarization, and Raman scattering depolarization. The absorption, emission, and Raman scattering spectra of linearly polarized light were recorded as a function of temperature in the whole range of the mesophase. On the basis of these spectra the order parameters P2 and P4 as well as the orientational distribution function were determined. The results obtained for members of various series with the same number of carbon atom in the alkyl chain were compared. It was found that the orientational order of liquid crystal molecules depends on the structure of the rigid core, on the kind of the terminal group as well as on the alkyl chain length. The odd-even effect for the order parameters, explained as the alteration of interaction between alkyl chains, was observed.

Smart, functional, or intelligent materials are no longer just theoretical systems; they now have applications in different fields of everyday life. One example of this class of materials with the potential for use in a wide range of applications is organic ionic gel (OIG) electrolytes, also known as gel electrolytes or ionogels. The functionality of OIGs arises from the thermally reversible solidification of electrolytes or ionic liquids and their superior conductivity properties. The performance of a series of ionogel samples made from a low molecular weight organic gelator (LMWG) and a quaternary ammonium salt electrolyte solution was studied by means of conductometry, thermal analysis, and microscopic observation. The solidification process was based on the sol-gel technique with controlled gelation temperature. The use of thermal scanning conductometry (TSC) allowed for in situ studies of the conductivity properties, reversibility, and reproducibility of the ionogel system in gel-sol-gel-sol phase transition cycles. As a result, the best chemical composition of the recoverable OIG system based on methyl-4,6-O-(p-nitrobenzylidene)-α-D-glucopyranoside (1) and tetramethylammonium bromide (TMABr) was determined in terms of its thermal and conductivity properties.

Langmuir and Langmuir-Blodgett (LB) films formed of some fluorescent dyes, derivatives of 4-aminonaphthalimide, and their binary mixtures with the liquid crystal 4-heptyl-4 -cyanobiphenyl (7CB) have been studied. Surface pressure versus mean molecular area isotherms for Langmuir films have given information about the alignment of molecules in a monomolecular layer at the air/water interface. The absorption and fluorescence spectra of LB films have revealed the occurrence of aggregates among dye molecules. In the ground electronic state some fraction of aggregates of J-type have appeared, while in the excited state the excimers have been created. The latter statement has been confirmed by additional absorption and fluorescence measurements performed for dyes dissolved in 7CB and placed in sandwich cells of 10 µm in thickness.

A general expression for the Poisson's ratio (PR) of square or 2D cubic materials is discussed in terms of the elastic moduli ratios, X=G/K and Y=G/W, where G and W are the shear moduli, and K is the bulk modulus. The entire XY‐plane is partitioned into nonauxetic, partially auxetic, and auxetic regions by two straight lines. A representation of the XY‐plane with the elastic constant ratio λ=C12/C44 is exploited to investigate 2D square materials under nonzero hydrostatic pressure. It is demonstrated that 2D square materials with λ>0 can be auxetic only under negative pressure. Similarities and differences between the corresponding descriptions of auxetic behavior of cubic 3D materials are pointed out.