In the present mini-review are discussed the findings reported in the last five years on the ion-conducting composites of polymers and molecules of nematic liquid crystals (NLCs), as well as their applications at present and in the future. Nowadays, free-standing and flexible thin films of such organic composite electrolytes synthesized from plastics and nematic soft matter are among the technically important materials and components for use in energy storage and conversion devices and in organic soft electronics, sensorics, and mechatronics. Although the physicochemical mechanisms and effects in the ion-conducting polymer/NLCs composites are well understood, the possibility to find additional ways for improving their electrical conductivity and dielectric and mechanical properties is a challenge. The efforts in this research direction are important for the development of novel ion-conductor materials and further diversification of their applications. This mini-review is focused on the key characteristics of ion-conducting polymer/NLCs composites and the new trends in their fabrication. With relevant examples, the vast research opportunities, some proposed improvements, and the creative ideas associated with these advanced materials and their intelligent use are outlined.

The stable and efficient photochromic and photoswitchable molecular systems designed from spirooxazines are of increasing scientific and practical interest because of their present and future applications in advanced technologies. Among these compounds, chelating spironaphthoxazines have received widespread attention due to their efficient optical response after complexation with some metal ions being of biomedical interest and environmental importance, as well as their good cycle performance and high reliability, especially by metal ion sensing. In this mini-review, we summarize our results in the design of novel photoswitchable chelating spironaphthoxazines with specific substituents in their naphthoxazine or indoline ring systems in view of recent progress in the development of such molecular systems and their applications as metal ion sensors. The design, synthesis methods, and photoresponse of such spirooxazine derivatives relevant to their applications, as well as quantum-chemical calculations for these compounds, are presented. Examples of various design concepts are discussed, such as sulfobutyl, hydroxyl, benzothiazolyl, or ester and carboxylic acid as substituents in the chelating spironaphthoxazine molecules. Further developments and improvements of this interesting and promising kind of molecular photoswitches are outlined.

The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness $10–25\mathrm{\mu m}$ and droplet size up to $50\mathrm{\mu m}$ exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He–Ne laser ($\lambda =633\mathrm{nm}$), an electrically commanded phase shift as large as $\pi /2$ can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light.

The electrically and spatially controllable coherent light diffraction by single-layered polymer-dispersed liquid crystal (PDLC) films is studied. Particularly, a wedge-formed thin film of E7/NOA65 microscale PDLC is examined. The PDLC single layer of thickness varying from a few micrometers to 25 μm contains liquid crystal (LC) droplets with double-truncated spherical shapes and a linear-gradient size distribution along the film length. The single-layer arrangement and compact packing of the micrometer-sized PDLC structure render the ellectrically-commanded coherent light diffraction controlled by LC/polymer interface.

Thin films (25 μm) of nanocomposites formed from nematic liquid crystal (LC) pentylcyano-biphenyl (5CB) doped with 0.5% wt. silver (Ag) nanospheres with a mean diameter ~ 10 nm were characterized by electrical measurements and dielectric spectroscopy in the frequency range from 1 mHz to 100 kHz. By using LC cells in which the electrodes are stripes of 1.2 mm width separated by a distance of 50 μm, it was possible to study the properties of Ag-5CB nematic nanocomposites by applying the external electric field either in the plane or perpendicular to the plane of the films. The results were compared with those obtained for undoped nematic 5CB in identical configurations of the experiments.