Polyamides containing thiadiazole units: Synthesis and optical properties

Highly refractive and transparent polyamides containing thiadiazole units have been developed. These polymers were prepared by a polycondensation reaction of 4,4′-(1,3,4-thiadiazole-2,5-thio) bis(methylene) dibenzoyl chloride (TDTBM-DC) and diamine which contained thioether (-S-) and sulfone units. They showed good thermal stabilities such as a relatively high glass transition temperature of 206–233 °C and a 5% weight-loss temperature (T _5%) of 376–395 °C. The optical transmittance of the polymer at 450 nm is higher than 83%. The heterocycle units and plural -S- linkages provide the polymer with a high refractive index of 1.716–1.725 at 633 nm and a low birefringence of 0.003–0.004. Also they showed improved solubility in polar aprotic solvents and could form moderate strength films with tensile strength of 72.8–83.1 MPa and storage modulus of 1.0–1.8 GPa (at 200 °C).