Fabrication of a stable poly(vinylpyrrolidone)/poly(urushiol) multilayer ultrathin film through layer-by-layer assembly and photo-induced polymerization

The fabrication of a stable poly(vinylpyrrolidone)/poly(urushiol) multilayer film was achieved through the UV irradiation of layer-by-layer self-assembled multilayer film consisting of poly(vinylpyrrolidone) and urushiol monomer. The assembling process, the driving force for construction, the thickness and hardness, and the morphological/structural changes of the multilayer film were investigated by Fourier transform infrared (FT-IR) spectroscopy, UV-vis spectroscopy, X-ray reflectometry (XRR), and atomic force microscopy (AFM), respectively. The structure of the multilayer film changed from sandwich to semi-interpenetrating networks (s-IPN) after photopolymerization. This resulted in great improvement in hardness while without destroying the well-defined layered structure of the film. The surface of the multilayer film is smooth and defect-free.