Photo-Reactive Polyimides and Poly(siloxane imide)s as Reversible Polymeric Interfaces

Polyimides and poly(siloxane imide)s containing photo-active cyclobutane diimide units were developed as reversible adhesives for temporary bonding in micro-fabrication processes. Poly(amic acid) formation in dipolar aprotic solvents and subsequent chemical or thermal solution imidization yielded the corresponding organic soluble polyimides. Incorporation of nonplanar (alicyclic or bicyclic) structures and poly(dimethyl siloxane) blocks into the main chain improved the solubility. The synthesized poly(siloxane imide)s afforded tough and ductile films, which exhibited a rubbery plateau in the storage modulus, as observed using dynamic mechanical analysis. This plateau was attributed to the microphase-separation of the poly(dimethyl siloxane) segments and the polyimide segments. Spin-coated thin films on silicon substrates were photo-degraded with ultraviolet-C (UVC) light (254 nm). Nuclear magnetic resonance (NMR) spectroscopy demonstrated a growth in the proton resonance corresponding to the formation of maleimide functionality upon photo-cleavage. This observed photo-cleavage suggests possible applications as temporary structural adhesives.