Novel soluble fluorine-containing polyamides derived from 2-(4-trifluoromethylphenoxy)terephthalic acid and trifluoromethyl-substituted aromatic bis(ether amine)s
A series of new fluorine-containing polyamides were prepared directly by polycondensation of 2-(4-trifluoromethylphenoxy)terephthalic acid with four trifluoromethyl-substituted aromatic bis(ether amine)s in N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride using triphenyl phosphite and pyridine as condensing agents. All the polymers showed excellent solubility in solvents such as NMP, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, pyridine, tetrahydrofuran, and acetone at room temperature. These polymers had inherent viscosities between 0.67 and 1.09 dL/g, and their weight-average molecular weights and number-average molecular weights were in the range of 48,200–68,000 and 29,500–39,400, respectively. The resulting polymers showed glass-transition temperatures between 189 and 214 °C and 10% weight loss temperatures ranging from 475 to 483 °C, and char yields at 800 °C higher than 50% in nitrogen. All polymers were amorphous and could be cast into transparent, flexible, and strong films from DMAc solutions with tensile strengths of 71–115 MPa, elongations at break of 6–9%, and tensile moduli of 2.7–3.2 GPa. These polymers had low dielectric constants of 3.14–3.31 (1 MHz), low moisture absorption in the range of 0.88–1.60%, and high transparency with an ultraviolet–visible absorption cut-off wavelength in the 320–340 nm range.