Tuning the aggregation of polyimide thin films by modification of their molecular interactions

Thin films of an organo-soluble polyimide based on 1,4-(3,4-dicarboxyphenox y)benzene dianhydride (HQDPA) and 2,2'-dimethyl-4,4'-methylene dianiline (D MMDA) have been studied. A prism coupler was used to measure the refractive indices. The average refractive indices of thin films prepared by annealin g at different temperatures and times were chosen to characterize the conde nsation states of thin films. Thin films annealed at 200 degrees C show irr eversible changes in physical properties, eg solubility. FTIR spectroscopy showed that the chain structures of the above thin films remained unchanged . It is proposed that specific molecular interactions induce the irreversib le changes revealed by fluorescence spectroscopy. (C) 2000 Society of Chemi cal Industry.