Synthesis and characterization of high refractive index polyimides derived from 4,4'-(p-phenylenedisulfanyl)dianiline and various aromatic tetracarboxylic dianhydrides

Abstract

A series of sulfur-containing polyimides with high refractive indices have been synthesized from an aromatic ulfur-containing diamine, 4,4'-(p- phenylenedisulfanyl)dianiline (2SPDA) and various aromatic tetracarboxylic dianhydrides via a two-step polycondensation procedure. 2SPDA was synthesized by the Williamson reaction of 4aminothiophenol with 1,4-dichlorobenzene in a yield of 75.8%. The flexible and tough polyimide films exhibited good thermal stability with the glass transition temperatures of 214.6-261.6 °C, the 5% weight loss temperatures of 509537 °C, and residual weights of 83-91 % at 550 °C in nitrogen. The films also exhibited the good transmittances of higher than 80% at 500 nm. The average refractive indices (nav) and in-plane/out-of-plane birefringence (△n) measured at 632.8 nm are in the range of 1.7117-1.7356 and 0.0074-0.0119, respectively. The good transparency in the visible region, high nav, and low △n of the PI films are very suitable for optical applications. © 2007 The Society ot Polymer Science.