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 TiO2 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.