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Summary: Titania‐containing coatings were prepared by cationic photopolymerization of an epoxy resin either by dispersion of preformed TiO2 nanoparticles or by their in‐situ generation through a sol‐gel dual‐cure process. The kinetics of photopolymerization was evaluated by real‐time FT‐IR, studying the effect of the TiO2 concentration. The properties of cured films were investigated, showing an increase of hydrophilicity on the surface of the coatings with increasing TiO2 content. TEM analysis demonstrated that it is possible to achieve a significantly better control of the dispersion of the inorganic particles within the organic matrix by in‐situ generation of TiO2, thus completely avoiding macroscopic phase separation and obtaining homogeneous, transparent coatings.Bright‐field TEM micrograph for TIP20 dual‐cured film.imageBright‐field TEM micrograph for TIP20 dual‐cured film.

Two different kinds of HBPs were used in the preparation of nanocomposite materials based on TiO 2 nanoparticles. One of the HBPs was characterized by the presence of free OH end groups in its structure, while the other one was obtained via a partial modification reaction which allowed to introduce some alkoxysilane functional groups. The TiO 2 particles were prepared in situ in the polymer solution by means of a sol-gel process starting from Ti(iOPr) 4 as precursor. The polymer/TiO 2 mixture, subsequently coated and cured in the presence of diisocyanate, gave rise to a hard coating. TiO 2 was found to be dispersed on nanometer scale inside the final coatings obtained from both the polymers, and the TiO 2 nanocomposite coatings were also characterized by improved thermal and hardness properties compared to TiO 2 free systems. Still the two different kinds of HBPs showed a different interaction with the TiO 2 particles, and it has been evidenced that the modification is required to achieve a better dispersion of the particles in the matrix and better properties for the final coating. Thus, by applying the modified HBP, TiO 2 could be dispersed and stabilized in the polymer matrix as individual nanoparticles of only 6 nm in diameter.

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