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 °C and 10% weight loss temperatures in excess of 424 °C in nitrogen and 469 °C in air atmosphere. The optical transmittances of the PA films at 450 nm were higher than 85% for the thickness of ∼10 μm. The combination of the thiazole moieties and flexible thioether linkages provided PAs with high average refractive indices (nav) of 1.7414–1.7542 and low birefringences (Δn) of 0.0061–0.0087 at 632.8 nm. In particular, the nav of PA-5 derived from DA and 2,2′-dithiodibenzoic acid exhibited the highest refractive index (1.7542) in the high refractive index PAs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3505–3515