Thermotropic mesogens typically exist as liquid crystals (LCs) in a narrow region of high temperatures, making lowering their melting point with the temperature expansion of the mesophase state an urgent task. Para-substituted benzoic acids can form LCs through noncovalent dimerization into homodimers via hydrogen bonds, whose strength and, consequently, the temperature region of the mesophase state can be potentially altered by creating asymmetric heterodimers from different acids. This work investigates equimolar blends of p-n-alkylbenzoic (kBA, where k is the number of carbon atoms in the alkyl radical) and p-n-alkyloxybenzoic (kOBA) acids by calorimetry and viscometry to establish their phase transitions and regions of mesophase existence. Non-symmetric dimerization of acids leads to the extension of the nematic state region towards low temperatures and the appearance of new monotropic and enantiotropic phase transitions in several cases. Moreover, the crystal–nematic and nematic–isotropic phase changes have a two-step character for some acid blends, suggesting the formation of symmetric and asymmetric associates from heterodimers. The mixing of 6BA and 8OBA most strongly extends the region of the nematic state towards low temperatures (from 95–114 °C and 108–147 °C for initial homodimers, respectively, to 57–133 °C for the resulting heterodimer), whereas the combination of 4OBA and 5OBA gives the most extended high-temperature nematic phase (up to 156 °C) and that of 6BA and 9OBA (or 12OBA) provides the existence of a smectic phase at the lowest temperatures (down to 51 °C).

For the first time, a laboratory technology has been developed for preparing poly(naphthoylene benzimidazole) incombustible nonwoven material by electrospinning from a solution of the precursor polymer, polyaminonaphthoyleneimide, through the thermal transformation stage. The influence of polymer concentration in solution and the voltage applied to the injection nozzle and collecting device on the properties of the resulting material was studied. The morphology of the new material was investigated, its mechanical, thermal, and thermomechanical characteristics were examined, and the limiting oxygen index was assessed. The optimal key operational parameters for electrospinning were determined, which constitute the essence of the laboratory technology for producing the new material.

Continuous hollow fibers have been obtained for the first time from solutions of poly(2,5(6)-benzimidazole) in phosphoric acid. The rheological behavior of the solutions has been studied, and the kinetics of precipitation of the dope solution with water and 40% NaOH solution has been investigated. It has been shown that water is a soft precipitant, whereas the concentrated alkali leads to hard coagulation and the formation of vacuole defects. The operating parameters of the fiber spinning, such as the ratio between the volumetric flow rate of the internal precipitant to the flow rate of the polymer solution and the nature of the internal precipitant have a decisive influence on the morphology of the resulting fibers. As a result, a laboratory technology for spinning of hollow fibers of poly(2,5(6)-benzimidazole) with a monolithic and asymmetric structure has been elaborated, their thermal properties have been investigated, the residual solvent content in the fiber has been estimated, and the value of the limiting oxygen index has been determined. It has been shown that the hollow fibers of poly(2,5(6)-benzimidazole) have a great potential for use in high-temperature membrane separation.