Adhesion behavior of PDMS-containing polyimide to glass

The effect of the incorporation of poly(dimethyl siloxane) (PDMS) segments into a poly[N,N'-(p,p'-oxydiphenylene) pyromellitimide] (PMDA-ODA) polyimide backbone on the adhesion between PMDA-ODA polyimide and glass was investigated using X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, contact angle measurements, and the peel test. The peel energy of PMDA-ODA polyimide to glass was significantly improved when low molecular weight PDMS (248.5 g/mol) was incorporated, while little improvement was observed for the incorporation of high molecular weight PDMS (900 or 1680 g/mol). Exposure to air resulted in a considerable deterioration in the peel energy for the pure PMDA-ODA polyimide, while no deterioration was observed for the PDMS-containing polyimides. The improvement in peel strength was successfully achieved by the incorporation of very small quantities of PDMS such as 2 wt%. Based on XPS, IR spectroscopy, and contact angle measurements, it is suggested that the incorporated PDMS segments migrated from the bulk polyimide to the polyimide/glass interface and chemically bonded to the glass surface, which resulted in enhancement of the peel energy. However, a weak boundary layer was formed between the bulk polyimide and glass when a high molecular weight PDMS (900 or 1680 g/mol) was incorporated and thus the peel energy deteriorated.