Stepwise Synthesis of a Well-Defined Silicon (Oxide)/Polyimide Interface

Self-assembly of 1-bromo-16-(trichlorosilyl)hexadecane leads to highly ordered bromide-terminated monolayer films on silicon (oxide) substrates. The bromides were converted to azides by treatment with sodium azide and then reduced to corresponding amines using lithium aluminum hydride. Protonation of these amine surfaces was difficult to reverse and rendered them unreactive toward electrophiles. The unprotonated form, however, reacted with molten phthalic anhydride to form the corresponding imide. These chemical transformations were characterized by ellipsometry, attenuated total reflectance infrared spectroscopy, contact angle goniometry, and X-ray photoelectron spectroscopy. Spin-coating of a polyamic acid, the precursor of poly-N, N-(4,4′-oxydiphenylene)pyromellitide, onto the pure amine-terminated surface, followed by curing (up to 350 °C), resulted in covalent linkages between the substrate and the polymeric coating. The success of this curing was confirmed by infrared spectroscopy. Adhesion test results showed that this amine-terminated monolayer enhanced the adhesion of polyimide films to these substrates.