Controlling Interfacial Interpenetration of Polymer Waveguide Deposited on Plasma Treated Flexible Substrate

The structural integrity of polymeric interfaces has been critical in enabling microelectronic applications. This paper demonstrates a systematic approach in investigating the strengthening of the polymeric interface between a thinly deposited polysiloxane optical cladding deposited onto flexible substrate. The surface of the polyimide substrate was modified with plasma treatment. Surface properties were analyzed with contact angle measurement, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Dynamic secondary ion mass spectrometry (SIMS) was used to characterize the interpenetration of the polysiloxane into the plasma-modified polyimide surface. The depth profile between the pristine and treated interface was verified with interfacial strength measurement using the double cantilever beam approach (DCB). We find that increasing the interphase width enhances the interfacial strength, resulted from a possible mechanism of enhanced entanglements between the polymer chains in the interface.