Hyperbranched polymer/TiO₂ hybrid nanoparticles synthesized via an in situ sol-gel process

Two different kinds of HBPs were used in the preparation of nanocomposite materials based on TiO₂ 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 TiO₂ 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/TiO₂ mixture, subsequently coated and cured in the presence of diisocyanate, gave rise to a hard coating. TiO₂ was found to be dispersed on nanometer scale inside the final coatings obtained from both the polymers, and the TiO₂ nanocomposite coatings were also characterized by improved thermal and hardness properties compared to TiO₂ 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, TiO₂ could be dispersed and stabilized in the polymer matrix as individual nanoparticles of only 6 nm in diameter.