Nanoparticle layer via UV-induced directional migration of iron-doped titania nanoparticles in polyvinyl butyral films and superior UV-stability

The migration of nanoparticles in polymer matrix is significant for the structure and performance of polymer nanocomposites after the initial formation. However, the understanding and controlling of migration of nanoparticles in polymer matrix remains a challenge. Herein, we report using ultraviolet (UV) light to perform the directional migration of inorganic nanoparticles in polymer film, generating an ultrathin (100–200 nm) nanoparticle layer on the light exposure surface of the film. The prepared iron-doped titania nanoparticles (Fe–TiO2) are initially uniformly dispersed into polyvinyl butyral (PVB) film, and homogeneous distribution remains unchanged even after thermal treatment. However, the UV irradiation induces the directional migration of nanoparticles towards the illuminated surface. The mechanism indicates that the directional migration of nanoparticles is related with the increase of interfacial energy and conformational entropic effect between Fe–TiO2 and PVB upon UV irradiation. The formed nanoparticle layer endowed the PVB/Fe–TiO2 film with superior UV-stability. Our work extends the study of controlling migration of nanoparticles in polymer matrix by applying external stimuli, and provides a novel strategy for the functionalization of polymer nanocomposite materials.