High solubility and optical transparency of novel polyimides containing 3,3′,5,5′-tetramethyl pendant groups and 4-tert-butyltoluene moiety

A series of novel polyimides (3a-d) were prepared from 3,3',5,5'-tetramethyl-4,4'-diaminodiphenyl-4 ''-tert-butyltoluene (1) with four aromatic dianhydrides via a one-step high-temperature poly-condensation procedure. The obtained polyimides showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most amide polar solvents and chlorinated solvents. Their films were nearly colorless and exhibited high optical transparency, with the UV cutoff wavelength in the range of 322-350 nm and the wavelength of 80% transparency in the range of 395-414 nm. They also showed low dielectric constant (2.72-2.91 at 1 MHz) and low water absorptions (0.37-0.62%). Moreover, these polyimides possessed high glass transition temperatures (T-g) (above 321 degrees C) and good thermal stability with 10% weight loss temperatures in the range of 526-547 degrees C in nitrogen atmosphere. In comparison with the analogous polyimides non-containing 3,3' 5,5'-tetramethyl pendant groups, the resultant polyimides 3a-d showed better solubility, higher optical transparency and lower dielectric constant. (c) 2009 Elsevier Ltd. All rights reserved.