Synthesis and properties of polyamides containing high contents of thioether units

Two kinds of monomers containing the thioether units 4,4′-thiodibenzoyl chloride (T-DC) and 4,4′-bis(4-chloroformylphenylthio)benzene (BPB-DC) were synthesized in two steps and were reacted with diamine-containing thioether (–S–) and sulfone units to prepare a polyamide containing high contents of thioether groups. The intrinsic viscosities of the polyamides were 0.81–0.93   dl/g. These polymers had good optical properties , including an optical transmittance of the aromatic polyamide film at 450   nm that was higher than 90%. Additionally, the high quantity of thioether units provided the polymers with high refractive indices of 1.710–1.716 and low birefringences of 0.007–0.009. These polyamides also had excellent thermal properties, with glass transition temperatures ( T g ) of 230–246   °C and initial degradation temperatures ( T d ) of 477–473   °C. Finally, they showed improved solubility in polar aprotic solvents .