Structure and mechanical properties of mesostructured functional hybrid coatings based on anisotropic nanoparticles dispersed in poly(hydroxylethyl methacrylate)

Colored hybrid coatings with efficient mechanical properties have been elaborated by introducing goethite ((alpha-FeOOH) nanorods and maghemite (gamma-Fe2O3) nanospheres in a poly(hydroxyethyl methacrylate) (PHEMA) matrix. The resulting hybrid coatings have been characterized with regard to the dispersion state of the particles, the swelling behavior of the PHEMA matrix, and the mechanical properties of the coatings. From a mechanical point of view, both goethite nanorods and maghemite nanospheres lead to a strong reinforcement effect of PHEMA, even at low volume fraction. The origin of such reinforcement is attributed to the existence of strong interactions at the iron oxide-PHEMA interface combined with a homogeneous dispersion of the particles. The nature and the strength of these interactions and evidence of their influence on the mechanical behavior of the nanohybrid coatings are reported. Moreover, the goethite-based hybrid coatings exhibit interesting birefringent properties associated with the stabilization inside the organic matrix of a liquid crystal-type organization resulting from the self-assembly of goethite nanorods.