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Certain nematic liquid crystals, for example, those formed by banana-shaped molecules, can exhibit a low-temperature twist-bend nematic (Ntb) phase. Upon addition of chiral dopants, a chiral version of the twist-bend phase (N*tb) can be observed below the conventional chiral nematic (N*) phase, while under electric field the N* phase is transformed into a specific state known as 'oblique helicoidal cholesteric'. In this work, we have studied the well-known Ntb-forming system CB7CB:CB6OCB with addition of 5CB and chiral dopants (ChDs) using optical microscopy, differential scanning calorimetry (DSC), and measurements of temperature-dependent optical transmission using optical microscopy. Effects of 5CB and different chiral dopants (of steroid or non-steroid nature) upon thermal stability of Ntb phase were analysed, and selective reflection in the visible range could be observed in the N* phase with a sufficiently high ChD content. As a peculiar feature, sharp unwinding of the cholesteric helix was observed at lower temperatures when approaching the N*tb phase, which appears to be similar to the helix unwinding close to the smectic-A transition. [ABSTRACT FROM AUTHOR]

Zeolite IPC-3 - which is isostructural with the extra-large pore germanate zeolite ASU-16 - and its Si, Al and Ti forms were synthesized using 1,6-diaminohexane as the template. It was established that the Si atoms occupy the tetrahedral positions in the IPC-3 framework, the Al atoms occupy the octahedral or tetrahedral positions and the Ti atoms the octahedral positions. The germanate zeolite IPC-3 and Si-, Al- and Ti-IPC-3 are stable up to 200-300°C. Despite the presence of the template, which stabilizes the framework of IPC-3, the adsorption capacities of samples previously degassed at 200°C were up to 0.13 cm3/g. [ABSTRACT FROM AUTHOR]

Abstract: Porous magnetic composites were prepared by the synthesis of molecular sieve MCM-41 in the presence of Fe3O4 nanoparticles with average diameter of 15nm. Nanoparticles were captured by porous silica matrix MCM-41, which resulted in their incorporation, as it was confirmed by TEM, SEM and X-ray diffraction. The materials possessed high surface area (392–666m2 g−1), high pore volume (0.39–0.73cm3 g−1) along with high magnetic response (M S up to 28.4emug−1 at 300K). Calcination of samples resulted in partial oxidation of Fe3O4 to α-Fe2O3. The influence of nanoparticles content on sorption and magnetic properties of the composites was shown. No hysteresis was found for the samples at 300K; at 5K, H C was in the range 370–385G for non-calcinated samples and 350–356G for calcinated ones. [Copyright &y& Elsevier]