Synthesis and Characterization of Organosoluble Aromatic Polyimides Containing POSS in Main Chain Derived from Double-Decker-Shaped Silsesquioxane

Preparation of low dielectric constant polyimides containing double-decker-shaped silsesquioxane (DDSQ) in the main chain with high molecular weights (η inh = 0.61 dL/g) is reported. Double-decker-shaped silsesquioxane aromatic tetracarboxylic dianhydride (DDSQDA) was prepared by reaction of DDSQ aromatic diamine and pyromellitic dianhydride through functional group conversion method. The polyimides were synthesized from DDSQDA and several aromatic diamines by a one-step high temperature solution method. Introduction of DDSQ unit in polyimides endowed properties such as solubility in organic solvents, 10% weight loss temperatures ( T d10 ) up to 570 °C in nitrogen, the glass transition temperatures ( T g ) higher than 300 °C, good mechanical properties (tensile strengths of 72.3–82.1 MPa, initial modulus of 1.8–2.6 GPa, and elongation at breakage of 8.0–15.9%), transmittances over 80% at 400 nm, and a dielectric constant of 2.43 at 1 MHz. The polyimides were soluble in organic solvents such as DMAc, chloroform, THF, and acetone.