Influence of chemical structure on the refractive index of imide-type polymers

Abstract

The influence of different substituents on the optical properties of poly(amide imide)s and polyimides is systematically investigated. All of the polymers exhibit good solubility and film-forming ability, high thermal stability, and glass transition temperatures of 162-209 °C for poly(amide imide)s and of 209-274 °C for polyimides. The optical transmittance of the films at 450 nm is above 80% for all the studied polyimides and poly(amide imide)s containing benzonitrile units linked in the 2,6-position. The values of refractive index for poly(amide imide)s are in the range of 1.623-1.748 and for polyimides in the domain of 1.672-1.768. The influence of various substituents on the refractive index value of two series of imide-type polymers is analyzed. Thus, the effect of the amide unit and the benzonitrile position in poly(amide imide)s and the presence of tetrabromo substituents and of flexible linkages in polyimides series are evaluated. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.