Synthesis and characterization of novel fluorinated polyamides bearing tetraphenyl imidazole moieties

Abstract

1,2-Bis(4-aminophenyl)-4,5-bis(4-trifluoromethylphenyl)-1H-imidazole, as a new asymmetric aromatic diamine, was synthesized and used for preparation of novel fluorinated polyamides (PAs) containing tetraphenyl imidazole moieties in the main chain by low-temperature polycondensation of the diamine with various aromatic dicarboxylic acid dichlorides. The resulting PAs were amorphous and their weight-average and number-average molecular weight were in the range of 22,500–34,600 and 12,600–16,800 g/mol, respectively. These PAs exhibited low moisture uptake of 0.97–2.15%, and good thermal stability with 10% weight loss temperatures of 445–453 °C and char yields of 57–61% at 800 °C in nitrogen. All obtained PAs showed good flame retardancy with limited oxygen index value of 39.9–41.9, and were readily soluble in a variety of organic solvents such as N,N-dimethyl acetamide, N-methyl-2-pyrrolidinone, dimethylsulfoxide, pyridine, tetrahydrofuran and acetone at room temperature, and formed low-colored and flexible thin films via solution casting. They also exhibited strong UV–vis absorption in the range of 290–320 nm in solution and in films, and their films exhibited high optical transparency with a cutoff wavelength in the 328–365 nm range.