Synthesis of high refractive index polyamides containing thioether unit

Two kinds of aromatic dibenzoyl chloride monomer containing thioether unit 4,4'-Bis(4-chloroformylphenylthio)benzophenone (BP-DC) and 4,4'-thiodibenzoyl chloride (T-DC) were synthesized with two steps, which was reacted with diamine monomer containing thioether and amide unit to prepare a new kind of polyamide containing high quantity thio-ether group. The intrinsic viscosity of the polyamides was 0.76-0.90 dl/g obtained with optimum synthesis conditions. The polymers were found to have good optical properties: the optical transmittance of the aromatic polyamide film at 450 nm is higher than 80%, meantime the high quantity thio-ether unit provided the polymer with a high refractive index ranging from 1.691 to 1.696 and low birefringence of 0.007-0.008. At the same time the polymers had excellent thermal performance with glass transition temperature (T(g)) of 226 A degrees C-278 A degrees C, initial degradation temperature (T(d)) of 427 A degrees C-439 A degrees C. They showed improved solubility in polar aprotic solvents.