Aliphatic Polybenzimidazoles: Synthesis, Characterization and High-Temperature Shape-Memory Performance.

A series of aliphatic polybenzimidazoles (PBIs) with methylene groups of varying length were synthesized by the high-temperature polycondensation of 3,3'-diaminobenzidine (DAB) and the corresponding aliphatic dicarboxylic acid in Eaton's reagent. The influence of the length of the methylene chain on PBIs' properties was investigated by solution viscometry, thermogravimetric analysis, mechanical testing and dynamic mechanical analysis. All PBIs exhibited high mechanical strength (up to 129.3 ± 7.1 MPa), glass transition temperature (≥200 °C) and thermal decomposition temperature (≥460 °C). Moreover, all of the synthesized aliphatic PBIs possess a shape-memory effect, which is a result of the presence of soft aliphatic segments and rigid bis-benzimidazole groups in the macromolecules, as well as strong intermolecular hydrogen bonds that serve as non-covalent crosslinks. Among the studied polymers, the PBI based on DAB and dodecanedioic acid has high adequate mechanical and thermal properties and demonstrates the highest shape-fixity ratio and shape-recovery ratio of 99.6% and 95.6%, respectively. Because of these properties, aliphatic PBIs have great potential to be used as high-temperature materials for application in different high-tech fields, including the aerospace industry and structural component industries.

Hydrothermal Synthesis of N-Doped Graphene for Supercapacitor Electrodes.

N-doped graphene based on graphene oxide and 3,3',4,4'-tetraaminodiphenyl oxide (TADPO) was obtained using a one-step hydrothermal process. The resulting materials were fully characterized using elemental analysis, infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron micrographs, and transmission electron microscopy. The findings reveal that benzimidazole rings were formed during the reaction, and the mass content of nitrogen in the obtained material varied from 12.3% to 14.7%, depending on the initial concentration of TADPO. Owing to the redox activity of benzimidazole rings, the new N-doped graphene materials demonstrated a high specific capacitance, reaching 340 F g-1 at 0.1 A g-1, which was significantly higher than that of the sample of reduced graphene oxide obtained under similar conditions without the use of TADPO (169 F g-1 at 0.1 A g-1). The resulting material also exhibited good cyclic stability after 5000 cycles.

From Aggregates to Porous Three-Dimensional Scaffolds through a Mechanochemical Approach to Design Photosensitive Chitosan Derivatives.

The crustacean processing industry produces large quantities of waste by-products (up to 70%). Such wastes could be used as raw materials for producing chitosan, a polysaccharide with a unique set of biochemical properties. However, the preparation methods and the long-term stability of chitosan-based products limit their application in biomedicine. In this study, different scale structures, such as aggregates, photo-crosslinked films, and 3D scaffolds based on mechanochemically-modified chitosan derivatives, were successfully formed. Dynamic light scattering revealed that aggregation of chitosan derivatives becomes more pronounced with an increase in the number of hydrophobic substituents. Although the results of the mechanical testing revealed that the plasticity of photo-crosslinked films was 5⁻8% higher than that for the initial chitosan films, their tensile strength remained unchanged. Different types of polymer scaffolds, such as flexible and porous ones, were developed by laser stereolithography. In vivo studies of the formed structures showed no dystrophic and necrobiotic changes, which proves their biocompatibility. Moreover, the wavelet analysis was used to show that the areas of chitosan film degradation were periodic. Comparing the results of the wavelet analysis and X-ray diffraction data, we have concluded that degradation occurs within less ordered amorphous regions in the polymer bulk.