The curing behaviour of the composition of a liquid-crystalline diepoxy monomer (LCEM) with the central triaromatic mesogenic group was studied using differential scanning calorimetry, conventional DSC and temperature-modulated TMDSC and nuclear magnetic resonance ¹H-NMR spectroscopy. The stoichiometric amount of primary aromatic diamine, 4,4′-diaminodiphenylmethane (DDM), was used as a curing agent. TMDSC TOPEM^® allowed the separation of the thermal effects related to reversible processes (e.g. phase transitions) from irreversible processes (cross-linking reaction) and determining that irreversible curing reaction occurs at the same time as reversible transition of the LCEM from crystal to the liquid-crystalline nematic phase. Additionally, ¹H-NMR analysis of the LCEM/DDM mixture preheated to a temperature from the temperature range of complex thermal changes was conducted. The obtained spectrum clearly showed the presence of partially cured products in the investigated samples and additionally proved that during the endothermic phase transition of the LCEM monomer an exothermic cross-linking reaction was occurring.

Reactive octahedral silsesquioxanes of rod-like [octakis(3-chloropropyl)octasilsesquioxane – T₈(CH₂CH₂CH₂Cl)₈] and spherical [octavinyloctasilsesquioxane – T₈(CHCH₂)₈] structure can undergo reversible thermally induced phase transitions in the solid state. The phase behaviour has been studied with differential scanning calorimetry (DSC, including temperature modulated DSC), X-ray diffraction, dielectric relaxation spectroscopy (DRS), and nuclear magnetic resonance spectroscopy in the solid state (SS NMR), as well as positron annihilation lifetime spectroscopy (PALS) and polarized optical microscopy (POM). The mechanisms involving fitting the molecules into most symmetrical crystal lattices vary for species of different structure. Thermal energy can be used to expand the crystal lattice leading to thermochromism in the case of T₈(CHCH₂)₈ or conversely to an unusual negative thermal expansion of crystals of T₈(CH₂CH₂CH₂Cl)₈ that results in their self-actuation. The complex behaviour is reflected in unusual changes in the capacitance and fractional free volume of the material. These phenomena can be used for molecular design of advanced well-defined hybrid materials capable of reversible thermally induced structural transformations. The findings present a new perspective for POSS-based flexible metal–organic frameworks (MOF) of cooperative structural transformability via entropy-based translational sub-net sliding.

The properties of two pairs of recently synthesised compounds with mesogenic unit were compared. The four compounds consist of a central segment (based on biphenyl or phenylbenzoate) with symmetric carbon chains ended with vinyl or epoxy groups. Typical measurement techniques (including microscopic observations, differential scanning calorimetry and wide-angle X-ray scattering and dielectric studies) were used to examine phase transitions in the studied materials. The phase transition sequences were determined for all materials. A liquid crystalline phase appeared in some cases. It was observed that replacing the functional group in the tails visibly changes the temperatures and sequences of phase transitions.

In this paper we investigate the dielectric response of cured epoxy resins based on biphenyl group. We chose two monomers, which were earlier synthesised, containing the same mesogen but with long and short symmetric tails. They were cured with standard amines (DDM, DMAP). Firstly we optimised conditions of the curing process by dielectric and optical observation in situ. Small differences in the dynamics of the curing process were observed in different mixtures. For the four selected products we made dielectric measurements in a wide range of frequency and temperature. Although, generally, dielectric response is similar in all the cured materials, differences can be seen in the details. At lower temperatures, quite strong relaxation process is seen in all products, its low activation energy points towards a β-process, which appears in many polymers. The Havriliak-Negami formula was fitted to the data and characteristic parameters of the observed relaxation processes were compared in detail. In some cases the α-process also appears. We conclude how the longer spacer and the type of curing process influence the electrical properties of the resin.