Synthesis and Characterization of a Self-Polycondensation Diazaphthalanone Monomer and Its Polymers from Polycondensation Reactions

Polyether ketone (PEK) plastics are linear thermoplastic polymers connected by at least one ether bond and at least one ketone bond on the aryl group. The reason for their excellent heat resistance, rigidity, and mechanical strength is that their main molecular chain contains plenty of aromatic rings and polar carbonyl groups, and their molecular chain presents a large rigidity and strong intermolecular force. In addition, the main chain contains a considerable number of ether bonds, resulting in a certain toughness. However, polyether ketone materials have the disadvantage of poor solubility because of their excellent rigidity. To improve the solubility of polyether ketone, the preparation method of a novel nitrogenous heterocyclic polyaromatic ether monomer, 2-(4-chlorophenyl)-2,3-dihydrophthalazine-1,4-dione (CDD), was proposed, and its activity of polymerization was studied. The average molecular weight of the poly(aryl ether ketone) containing a nitrogenous heterocyclic polyaromatic ether group obtained by self-polycondensation of CDD was 4.181 × 10³ kg/mol, and the yield was 90.5%. In order to further explore the activity of monomers, novel copolymerized poly(aryl ether ketone) (PBCD) containing a nitrogenous heterocyclic polyaromatic ether structure was prepared by ternary copolymerization with 4,4-difluorobenzophenone (DFBP) and bisphenol fluorene (BHPF) with high activity. The average molecular weight of PBCD was 72.793 × 10³ kg/mol, the molecular weight distribution was 2.344, and the yield was 88.1%. Fourier transform infrared spectroscopy (FT-IR) and ¹H NMR were used to confirm the structure of the obtained polymer. Through thermogravimetric analysis (TGA), the determined weight loss temperature of 5% under nitrogen was higher than 500 °C, indicating excellent thermal stability. Compared with the solubility of the binary copolymer containing fluorenyl poly(aryl ether ketone) (PBD), the polymer showed reasonable solubility in selective solvents such as chloroform and N,N-dimethylacetamide.

New poly(aryl ether ketone)s containing 2,6-diphenylpyridyl units and diphenylphosphinophenyl pendant groups

4-(4-Diphenylphosphino)phenyl-2,6-bis(4-hydroxyphenyl)pyridine, as a new bisphenol monomer, was prepared from 4-(diphenylphosphino)benzaldehyde and 4-hydroxyacetophenone and used in the preparation of several aromatic poly(ether ketone)s (PEKs) containing 2,6-diphenylpyridyl units and diphenylphosphinophenyl pendant groups via a nucleophilic aromatic substitution polycondensation with difluorinated aromatic ketones. The polycondensation proceeded quantitatively in tetramethylene sulfone in the presence of anhydrous potassium carbonate and afforded the polymers with high molecular weights. The resulting PEKs are amorphous and exhibit high glass transition temperatures of 209–255°C and 5% weight loss temperatures of 536–554°C with char yields of 57–62% at 800°C in nitrogen. Their high char yields and good limited oxygen index values ranging from 39 to 43 indicated these polymers exhibited good thermal stability and flame-retardant property. All new PEKs were soluble in common organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and chloroform and could form tough, flexible, and strong films with tensile strengths of 74.6–86.8 MPa, tensile moduli of 2.9–3.6 GPa, and elongations at break of 5–9%.

Synthesis and biological evaluation of pyridinium-functionalized carbazole derivatives as promising antibacterial agents

Various pyridinium-functionalized carbazole derivatives were constructed by coupling the key fragments of carbazole skeleton and pyridinium nucleus in a single molecular architecture. Antibacterial bioassays revealed that some of the title compounds displayed impressive bioactivities against plant pathogens such as Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Xanthomonas axonopodis pv. citri with minimal EC₅₀ values of up to 0.4, 0.3, and 0.3mg/L, respectively. These bioactivities were achieved by systematically tuning and optimizing bridging linker, alkyl length of the tailor, and substituents on the carbazole scaffold. Compared with the bioactivity of the lead compound (AP-10), antibacterial efficacy dramatically increased by approximately 13-, 104- and 21-fold. This finding suggested that these compounds can serve as new lead compounds in research on antibacterial chemotherapy.

Synthesis and characterization of novel high-performance polyarylsulfones with 4-(carbazol-9-yl) triphenylamine moieties

A novel homopolyarylsulfone with 4-(carbazol-9-yl) triphenylamine moieties was synthesized successfully through N–C coupling reactions under similar conditions to the synthesis of polyarylsulfones (PSU). By using this simple method and adjusting the feed ratio between 9-(4-aminobenzene) carbazole (NH2–Ar–Cz) and bisphenol A, a series of high-performance copolymers with high molecular weight, good film-reforming ability, great thermal stability, and excellent photoelectric characteristics were also prepared, which have good application potential in the field of organic optoelectronics.