Intramolecular Charge Transfer In Aromatic Polyimides

Abstract

ABSTRACTThe use of polyimides in integrated circuits to planarize complex topography and the need to decrease the dimensions of electronic devices have motivated us to gain a better understanding of the details of the polymer microenvironment. UV/Vis absorption experiments suggest that intramolecular charge transfer (ICT) exists and therefore might utilized as intrinsic, nonperturbing probes. The transfer of charge is believed to occur upon exposure of ultraviolet light as a result of donation from the phenyl ring (from the diamine fragment) to the adjacent imide ring. Furthermore, the transfer of charge should be a function of the torsional angle between the planes of the donor and acceptor segments.In this study, we first investigate the nature of the ICT by conducting UV/Vis absorption measurements on a series of model compounds. A comparative analysis of 10−5 M solutions of the models in dioxane provides evidence that intramolecular charge transfer occurs when the compounds are exposed to 264 nm (ultraviolet) light. Similarly, a comparison of an analogous series of polyimides demonstrates that the same phenomenon occurs in the more complex polymeric systems when spin-cast films are exposed to 326 nm (ultraviolet) light