Highly refractive and organo-soluble poly(amide imide)s based on 5,5′-thiobis(2-amino-4-methyl-thiazole): Synthesis and characterization

A new thioether-bridged diimide-diacid (DIDA) monomer was synthesized from the condensation of 5,5′-thiobis(2-amino-4-methyl-thiazole) (DA) and trimellitic anhydride at 1 : 2 molar ratio. A series of novel organic-soluble poly(amide imide)s (PAIs) bearing flexible thioether linkages and heteroaromatic thiazole groups were synthesized from DIDA with various commercially available aromatic diamines (1–5) via a direct polycondensation method with triphenyl phosphite and pyridine. The resulting polymers were obtained in high yields and possessed inherent viscosities in the range of 0.47–0.91 dL g^–1. All of the polymers were amorphous in nature, showed good solubility and could be easily dissolved in amide-type polar aprotic solvents (e.g., N-methyl-2-pyrrolidone, dimethyl sulfoxide, and N,N-dimethylacetamide), and even dissolved in less polar solvents (e.g., pyridine and tetrahydrofuran). They showed excellent thermal stability with glass transition temperatures between 233–269°C and 10% weight loss temperatures in excess of 480°C in nitrogen and 450°C in air atmosphere. The flexible structure endowed the PAI films with good optical transparency. The optical transmittances of the PAI films at 450 nm were higher than 80% for the thickness of approximately 10 μm. Moreover, the thiazole moieties and flexible thioether linkages in the molecular chains of the PAIs provided them with high refractive indices of 1.7329–1.7509 and low birefringences of 0.0065–0.0098. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012