We have synthesized a fully soluble and low-temperature processable polyimide-based gate insulator (PI-H1) through one-step polymerization of the monomers 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 1,5-naphthalenediamine. Fully imidized PI-H1 was found to be completely soluble in common organic solvents such as cyclohexanone. Thermal gravimetric analysis (TGA) exhibited that PI-H1 is stable up to 523 degrees C with only 5% weight loss. Thin films of PI-H1 could be fabricated at only 130 degrees C and a pentacene thin-film transistor (TFT) with PI-H1 as a gate dielectric was found to exhibit a field effect mobility of 0.13 cm(2)/Vs. When even thin films of PI-H1 gate dielectric were thermally stressed up to 400 degrees C, almost no TFT performance drop was observed. Our new low-temperature processable and excellent heat resistance PI-H1 shows promise as a gate dielectric for TFT. (c) 2010 Elsevier B.V. All rights reserved.