Mechanical Behavior of Functional Hybrid Coating Based on Anisotropic Iron Oxide Nanoparticles

Abstract

ABSTRACTFunctional hybrid coatings have been elaborated from a polymer matrix incorporating iron oxide nanoparticles. Stable aqueous suspensions of goethite (α-FeOOH) nanorods, obtained by controlled precipitation of Fe3+ ions, were introduced in 2-hydroxyethyl methacrylate (HEMA). The films were spin-coated on glass substrates from the solutions prior to a UV light induced free radical polymerization step. Nanoindentation tests were carried out to investigate the mechanical properties of the hybrid coatings. Swelling measurements and Fourier Transformed Infrared Spectroscopy (FTIR) were used to characterize the interface between the iron oxide nanoparticles and the PHEMA matrix. Cross-sectional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was performed to evaluate the dispersion state of the iron oxide particles through the matrix. From a mechanical point of view, iron oxide nanorods yield to a strong reinforcement effect of PHEMA (increase in modulus and hardness by a factor 2 with 5%vol goethite nanoparticles). Origins of such reinforcement are attributed to the existence of highly favourable interactions at the goethite-PHEMA interface combined with a homogeneous dispersion of the particles. The nature of these interactions and evidences of there influence on the mechanical behaviour of the nanohybrid coatings are reported.