Study of the morphology and texture of poly(3caprolactone)/polyethylene oxide blend films as a function of composition and the addition of nanofillers with different functionalities

Films of a blend of semi-crystalline polymers, namely poly(3-caprolactone) (PCL) and poly(ethylene oxide) (PEO), are prepared by casting drops of ethyl lactate (EL) polymer solutions onto a glass substrate. The goal of this work is to assess how the surface structure of the blend films can be controlled by: (i) varying the relative amounts of the polymeric components, and (ii) adding inorganic nanoparticles (NPs) with different functionality. Specifically, four types of NPs are used here: bare and silanized titanium dioxide, hydroxyapatite and aluminum-magnesium layered double hydroxide. All the films exhibit a segregated surface morphology, characterized by either PEO-rich domains dispersed in a PCL continuous phase or discrete PCL domains embedded in a PEO-rich phase, depending on the composition of the blend. Phase inversion occurs within the 30-40% range of PEO weight fraction. The incorporation of NPs to the starting polymeric solution is found to significantly affect the final blend morphology, leading to either a coarsening or a refinement of the polymer phases mainly according to the chemical affinity between the NPs and the suspending medium.