Solution processable polyamides containing thiazole units and thioether linkages with high optical transparency, high refractive index, and low birefringence

A series of new organic-soluble polyamides (PAs) bearing flexible thioether linkages and heteroaromatic thiazole units were synthesized from a novel thioether-bridged diamine monomer (DA) and various commercially available aromatic dicarboxylic acids (1-5) via a direct polycondensation method. The resulting polymers were obtained in high yields and possessed inherent viscosities in the range of 0.41-0.80 dL g(-1). All of the polymers were amorphous in nature, exhibited good solubility and could be easily dissolved in amide-type polar aprotic solvents and even dissolved in less polar solvents (e.g., tetrahydrofuran, pyridine, and acetone). They showed excellent thermal stability with glass transition temperatures between 207 and 239 degrees C and 10% weight loss temperatures in excess of 424 degrees C in nitrogen and 469 degrees C in air atmosphere. The optical transmittances of the PA films at 450 nm were higher than 85% for the thickness of approximate to 10 m. The combination of the thiazole moieties and flexible thioether linkages provided PAs with high average refractive indices (n(av)) of 1.7414-1.7542 and low birefringences (n) of 0.0061-0.0087 at 632.8 nm. In particular, the n(av) of PA-5 derived from DA and 2,2-dithiodibenzoic acid exhibited the highest refractive index (1.7542) in the high refractive index PAs. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3505-3515