Synthesis and properties of novel soluble fluorinated polyamides containing pyridine and sulfone moieties

A new diamine containing pyridine and trifluoromethylphenyl groups, 4-(4-trifluoromethylphenyl)-2,6-bis(4-aminophenyl)pyridine, was synthesized and used in the preparation of the fluorinated polyamides containing pyridine and sulfone moieties with inherent viscosities of 0.70–1.06 dL g−1 by the low temperature polycondensation with 4,4′-sulfonyl dibenzoyl chloride, 4,4′-[sulfonyl bis(4-phenyleneoxy)]dibenzoyl chloride, 3,3′-[sulfonyl bis(4-phenyleneoxy)]dibenzoyl chloride and 4,4′-[sulfonyl bis(2,6-dimethyl-1,4-phenyleneoxy)]dibenzoyl chloride in N,N-dimethylacetamide (DMAc) solution containing pyridine, respectively. All the polymers are amorphous and readily soluble in organic solvents such as DMAc, N-methyl-2-pyrrolidinone (NMP), N,N-dimethylformamide, dimethyl sulfoxide, pyridine (Py), and tetrahydrofuran at room temperature. The resulting polymers showed glass transition temperatures between 280 and 318 °C and 10% weight loss temperatures ranging from 485 °C to 516 °C, and char yields at 800 °C higher than 50% in nitrogen. All polymers could be casted into transparent, flexible and strong films from DMAc solutions with tensile strengths of 72–81 MPa, elongations at break of 12–15%, and tensile moduli of 1.8–2.1 GPa. These polymers had low dielectric constants of 3.40–3.51 (1 MHz), low moisture absorption in the range of 1.08–1.28%, and high transparency with an ultraviolet–visible absorption cut-off wavelength in the 374–382 nm range.