In this work, we report for the first time on the influence of polyhedral oligomericsilsesquioxanes (POSS) on the structure and properties of liquid crystalline polyurethane (LCPU). LCPU/POSS hybrids were synthesized via a two-step method. In the first step, 4,4′-methylenephenyl diisocyanate (MDI) and polytetramethylene ether glycol (PTMG) reacted with functionalized trisilanolphenyl POSS (TSP-POSS) bearing three hydroxyl groups. In the second step, the growing chain was extended with 4,4′-bis(hydroxyhexoxy)biphenyl (BHHBP). FTIR measurements confirmed the chemical bonding between the POSS and LCPU matrix and showed the influence of the silsesquioxane modification on the intensity of hydrogen bonds. The DSC and POM techniques confirmed the formation of liquid crystalline phases. The incorporation of silsesquixanes into the LC matrix leads to higher melting and isotropization temperatures along with the broadening phase transition effect. Scanning electron microscopy showed a good distribution of POSS moieties, both in the bulk and on the surface of the liquid crystalline PU matrix, whereby wide-angle X-ray diffraction (WAXD) patterns revealed halos from both the liquid crystalline and unmodified polyurethane matrix. The stress at the breaking points for LCPU/POSS hybrids containing 50% and 60% of elastic segments is greater than the stress at the breaking point of the reference material (LCPU), what is due to good dispersion of POSS in less elastic matrix. Thermal properties of the LCPU/POSS materials obtained, determined by TGA, revealed that the char residue increased with the amount of POSS for 40% of elastic segments materials.

Four chiral dopants exhibiting smectic LC phases themselves were prepared and their helical twisting power (HTP) and thermal phase behaviour in mixtures with four various LC hosts were studied. The influence of host liquid crystal on HTP was evaluated and generally higher values were found for hosts with high birefringence. Unexpectedly, high enhancement was found for an LC-chiral dopant pair, both having a similar aromatic core – biphenyl ring substituted with polar group. All studied chiral dopants exhibited limited compatibility with the LC hosts in twisted nematic phase at room temperature. For one of the studied mixtures, it was able to obtain single twisted nematic phase with selective light reflection band with maximum at wavelength about 1.0 µm. Carboxylic acid-type dopants exhibited total compatibility with the studied host in single twisted nematic phase at elevated temperatures, allowing preparation of mixtures with reflection band in the visible range. In case of the carboxylic acid dopants, blue phases for optimised compositions were observed. Intermolecular hydrogen bonding between carboxylic acid proton and pyridine nitrogen of chiral dopants was found. Doping the LC host with these dopants led to slight enhancement of HTP value and higher solubility in the LC host. Graphical abstract

Electron beam patterning is an important technology in the fabrication of miniaturized photonic devices. The fabrication process conventionally involves the use of radiation sensitive polymer-based solutions (called resists). We propose to replace typical polymer resists with eco-friendly solvent-free room temperature ionic liquids (RTILs), which are polymerized in situ and solidified by an electron beam. It is demonstrated that the shapes of polymerized structures are different for high-viscous Cl-based RTILs and low-viscous NTf2-based RTILs. Due to the the satisfactory quality of the polymerized spatial microstructures and their light transmission properties, the RTIL-derived microstructures are potentially attractive as photonic elements for near-infrared.

Formation of gratings upon alternating electric field in compositions of highly birefringent liquid crystal (LC) with novel chiral ionic liquid (CIL) enclosed in 10-µm-thick cells is studied. The compatibility of two organic components of the mixture is investigated. The grating is formed in 1–5% CIL mixtures and causes significant changes of the transmission of polarised light through the cells. Transmission of polarised λ = 633 nm light through the 5% CIL sample is studied with respect to frequency (1 Hz–3 MHz) and amplitude (up to 10 V) of alternating voltage and the results are used for sketch a voltage–frequency phase diagram. Two possible ways of formation of the gratings with perpendicular orientation to that formed from initial state are presented. Two twisting axes in the molecular alignments of the cholesteric LC gratings with perpendicular directions are proposed. Optical switch based on four different states of LC including two gratings with perpendicular directions is proposed. Moreover, behaviour of the rotation of a grating induced by AC field in hybrid planar-homeotropic cell is studied in two frequency regimes and rotation by more than 90° upon change of the AC field amplitude is observed. GRAPHICAL ABSTRACT