Plasma polymer films of tetravinylsilane modified by UV irradiation

As-deposited plasma polymer films of tetravinylsilane were modified by UV irradiation at ambient conditions. Surface and bulk spectroscopic techniques confirmed significant changes in chemical composition and structure that resulted in increased mechanical constants (Young's modulus, hardness) and density of the material due to the formation of a stronger polymer network with higher cross-linking. A decrease of the refractive index and extinction coefficient of the UV-irradiated material was caused by UV-induced chain scission and subsequent oxidation of the plasma polymer network. The surface morphology (RMS roughness) and wettability (surface free energy) of films can be controlled by UV exposition time. The most intensive aging effect was observed for the as-deposited film; in contrast, the 1000-min-UV-irradiated film appeared stable over 134 days. UV treatment can be characterized as an effective tool for additional tailoring of plasma polymer films according to their applications.