Structure and imidization of polyamic acid salt Langmuir-Blodgett films

Polyimide Langmuir-Blodgett (LB) films were prepared with a Pyromellitic dianhydride-4, 4' oxydianiline precursor, and the properties of the polyamic acid salt monolayer characterized by different methods. The pi-A relationship revealed that the precursor monolayer exhibits anisotropy on the water surface, the Wilhelmy plate being more sensitive to pressure when it is perpendicular to the compression direction. FTIR results showed that polyamic acid salt LB films have lower imidization energy than the corresponding painting films and can be imidized at lower temperature. The molecular arrangement in the LB films was studied by X-ray diffiraction and polarized FTIR, showing that the polyamic acid salt LB film is of Y-type, in which the molecules are highly oriented, with the main chain lying parallel to the substrate and the long fatty acid chains stretching out at a certain angle. (C) 2002 Society of Chemical Industry.