Modern optics and photonics constantly require break‐through materials and designs in order to achieve miniature, lightweight, highly tunable, and effective optical devices. One of the basic optical components is the diffraction grating (DG), widely used for the dispersion of light, beam steering, etc. This review gathers research efforts on diffractive optical elements based on cholesteric liquid crystal (CLC) materials with a supramolecular helical architecture. All main types and fabrication approaches of periodic diffractive structures from CLCs are classified and described. Key optical properties of DGs, their advantages and drawbacks are considered. Special attention is paid on the tunability of DGs including design principles and prospective chiral materials. The review consists of three parts divided according to the formation mechanism of diffractive structures: i) the spontaneously formed periodic structures from CLCs confined in cells with hybrid or homeotropic boundary conditions; ii) DGs generated by external electric field applied to CLCs layers; iii) light‐generated DGs (e.g., obtained by holography, mask exposure, photoalignment). The review also aims to initiate and gain collaborations between physicists, engineers and organic chemists to combine novel chiral photoswitches and molecular motors with sophisticated optical design paving the way towards novel smart optical materials.
An approach to the synthesis of a new class of liquid crystalline (LC) compounds, dendrimers of regular structure with terminal mesogenic groups, was elaborated. LC dendrimers based on the carbosilane dendritic matrix of first generation were synthesized. Cyanobiphenyl, methoxyphenyl benzoate and cholesteryl groups were used as mesogenic fragments. Individuality and structure of all compounds obtained was proved by GPC together with 1H- and 29Si NMR methods. The mesomorphic behaviour and structure of the LC dendrimers synthesized were investigated. It is argued that different mesophases of the smectic type are realized in all cases. It is shown that the mesophase type of these compounds essentially depends on the chemical nature of the mesogenic groups.
Microporous films of polyolefins, namely, polyethylene and polypropylene, have been prepared using the process based on the extrusion of the melt with the subsequent annealing, uniaxial extension,...