Synthesis and Structural Characterization of Pyridine-2,6-dicarboxamide and Furan-2,5-dicarboxamide Derivatives

Derivatives based on pyridine-2-6- and furan-2,5-dicarboxamide scaffolds reveal numerous chemical properties and biological activities. This fact makes them an exciting research topic in supramolecular and coordination chemistry and in discovering new pharmacologically-active compounds. This work aimed to obtain a series of symmetrical pyridine-2-6- and furan-2,5-dicarboxamides through a condensation reaction of the appropriate acyl chlorides and aromatic amides. Successful syntheses were confirmed with NMR spectroscopy. We solved their crystal structures for seven compounds; two pyridine and five furan derivatives. Based on our crystallographic studies, we were able to indicate supramolecular features of the crystals under investigation. Additionally, Hirshfeld surface analysis allowed us to calculate a distribution of intermolecular contacts in the dicarboxamide crystals.

Preparation and Property of Bio-Polyimide/Halloysite Nanocomposite Based on 2,5-Furandicarboxylic Acid

Bio-based polyimide (PI)/halloysite nanotube (HNT) nanocomposites based on 2,5-furandicarboxylic acid were prepared by in situ polymerization. The pristine HNTs were modified by tetraethoxysilane (TEOS) and 4,4′-oxybisbenzenamine (ODA). The bio-based PI/HNT nanocomposite film exhibited lower moisture absorption than pure bio-based polyimide, showing that the water resistance of the bio-based polyimide film was improved. The thermal stability and glass transition temperature (Tg) of PI/HNTs nanocomposites were improved with the addition of modified HNTs. Both the tensile strength and Young’s modulus of bio-based PI/HNTs nanocomposite films were enhanced. A 37.7% increase in tensile strength and a 75.1% increase in Young’s modulus of bio-based PI/HNTs nanocomposite films, with 1 wt% of the modified HNTs, were achieved. The result confirmed that 2,5-furandicarboxylic acid could replace the oil-based material effectively, thus reducing pollution and protecting the environment. Finally, a preparation mechanism to prepare bio-based PI/HNTs nanocomposite is proposed.

Polyimides from 2,5-bis[4-(4-aminophenoxy)benzoyl]furan and their thermal crosslinking reaction

Several polyimides were prepared via two-step polycondensation from novel 2,5-furandicarboxylic acid–based diamine, 2,5-bis[4-(4-aminophenoxy)benzoyl]furan, with commercial dianhydrides. The chemical structures of the monomers and polymers were characterized by FT-IR and NMR in detail, respectively. The polyimides exhibited high performances with 5 wt% weight loss temperatures of over 410 oC, glass transition temperatures of over 214 oC, and tensile strengths and Young’s moduli of up to 130 MPa and 3.2 GPa, respectively. The thermal crosslinking mechanism was studied by FT-IR, Raman spectroscopy, and model reaction analysis, which showed the Diels–Alder reaction between the furan group and diphenylethylene group was the main reaction. The crosslinked polyimide films showed improved solvent resistance, and thermal and mechanical properties.

Morphology-Controlled Self-Assembly and Synthesis of Biopolyimide Particles from 4-Amino-l-phenylalanine

Self-assembling polyimides (PIs) having diketopiperazine (DKP) components were synthesized by polycondensation of a 4-amino-l-phenylalanine (4APhe) dimer, an aromatic diamine newly designed in this study. The amino acid-derived PIs showed high thermal resistance, with a 10% weight loss temperature (T _d10) of 432 °C at the maximum, and did not show any glass transition below the thermal decomposition temperature. The poly(amic acid) (PAA) precursors formed nanospheres upon reprecipitation over dimethylacetamide into water. The nanospheres were then added to solvents with different polarities and sonicated to induce deformation of the spherical forms into spiky balls, flakes, or rods. The PAA particle morphologies were retained in the PIs after the two-step imidization. Finally, the PI particles with self-assembling DKP moieties were formed, and their morphologies were fine-tuned using different mixed solvents.

Enzymatic Polymerization of Dimethyl 2,5-Furandicarboxylate and Heteroatom Diamines

Previously, we have synthesized a diverse range of 2,5-furandicarboxylic acid (FDCA)-based semiaromatic polyamides via enzymatic polymerization. This novel class of polymers are biobased alternatives to polyphthalamides, which are petrol-based semiaromatic polyamides. From a commercial perspective, they have interesting properties as high-performance materials and engineering thermoplastics. It is even more appealing to explore novel FDCA-based polyamides with added functionality, for the development of sustainable functional materials. Here, a set of FDCA-based heteroatom polyamides have been successfully produced via Novozyme 435 (N435)-catalyzed polymerization of biobased dimethyl 2,5-furandicarboxylate with (potentially)heteroatom diamines, namely, 4,9-dioxa-1,12-dodecanediamine (DODA), diethylenetriamine, and 3,3-ethylenediiminopropylamine. We performed the enzymatic polymerization in solution and bulk. The latter approach is more sustainable and results in higher molecular weight products. Among the tested heteroatom diamines, N435 shows the highest catalytic activity toward DODA. Furthermore, we find that all obtained FDCA-based heteroatom polyamides are amorphous materials with a relatively high thermal stability. These heteroatom polyamides display a glass-transition temperature ranging from 41 to 107 °C.