Surface defect formation in polyimide film via ion migration from glass substrate

Abstract Migration of ions such as sodium from a glass surface to organic materials in contact is critical for the use of glass as a supporting material for film casting. In this study, we report the surface defect formation of annealed poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PMDA-ODA) film after detaching the film from soda-lime glass via ion migration. The defect was porous and sodium was observed as one of the major impurities in the defect. We propose that these defects form as a result of the ion migration from glass and thermal decomposition of PMDA-ODA. The ions released from glass at a sufficiently high temperature form hydroxide compounds during the floating of the film on water and readily attacks the imide ring at the glass-film interface. The ionic bonds are broken by thermal annealing and spread out and finally form defects by both segregation of ions to the film surface and PMDA-ODA decomposition.