Synthesis and characterization of new alkali-soluble polyimides and preparation of alternating multilayer nano-films therefrom

New alkali-soluble aromatic polyimides were prepared by a direct one-step polycondensation of 3,6-di(4-carboxyphenyl)pyromellitic dianhydride with common aromatic diamines in the presence of isoquinoline at 170 °C. The obtained polymers with inherent viscosities of the 0.62–1.01 g/dl range were all amorphous and highly soluble in dilute aqueous NaOH and tetramethylammonium hydroxide. Upon heating in TGA, the carboxylic acid groups degraded away at lower temperatures and the chain backbone did at higher temperatures. In DSC, no glass transition could be detected before decomposition. The alternating multilayer nano-films from the polyimides and poly(ethyleneimine) were prepared by the molecular self-assembly method and characterized by ellipsometry and X-ray reflectivity.