Synthesis and Characterization of Soluble Polyimides Derived from the Polycondensation of 2,6-bis(4-amino-2-trifluoromethylphenoxy-4'-benzoyl)pyridine with Some Aromatic Dianhydrides

Abstract

A new aromatic diamine monomer containing both pyridine and fluorine, 2,6-bis(4-amino-2-trifluoromethylphenoxy-4 '-benzoyl)pyridine (BAFP), was successively synthesized by the nucleophilic substitution reaction of 2,6-bis(4,4'-dihydroxybenzoyl)pyridine with 2-chloro-5-nitro-trifluoromethylbenzene in the presence of k2CO 3 in N, N-dimethylacetamide, and followed by reduction with SnCl2 and HCl in ethanol. The polycondensation of BAFP with four aromatic dianhydrides afforded a series of novel aromatic polyimides containing both pyridine and fluorine. The reaction was conducted by the one-step thermal imidization method. The resulting polyimides were characterized for inherent viscosity, solubility, and thermo-oxidative stability. The polyimides exhibited excellent solubility in various solvents such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO) and chloroform. The glass-transition temperatures ( Tg) were in the range of 206—227°C. The polyimides displayed good thermal stability, e.g. the temperatures at the 5% weight loss range were at 487—543°C in nitrogen and 463—521°C in air, respectively. Wide-angle X-ray diffraction measurements revealed that the polyimides were predominantly amorphous.