Nanostructured organic-inorganic polymeric coatings were prepared by UV-initiated cationic polymerization of epoxy resins. The inorganic part was either introduced in the form of silica nanoparticles or generated in situ via the sol-gel process in the presence of an organic precursor (TEOS). In the first case [1] the addition of silica nanoparticles increased the rate of photopolymerization and induced a slight increase on Tg values, together with a clear increase on modulus in the rubbery region. These data suggest a uniform distribution of silica into the epoxy matrix and a good interfacial adhesion between the filler and the matrix. This was confirmed by TEM morphology investigations that showed the silica particles were not highly aggregated and their size distribution ranges from 5 to 50 nm. In the latter case [2] the hybrid system networks were prepared through a dual-curing process, which involves photopolymerization and condensation of alkoxysilane groups. The obtained films were perfectly transparent and amorphous. DMTA analysis revealed a small increase of Tg values for the hybrid system with a broadening of the tan delta peak. The influence of the silica content on the damping peak amplitude suggests that silica is molecularly dispersed in the polymer matrix and that it significantly hinders the segmental motion of the polymer chains. TEM analyses showed the absence of any macroscopic phase separation and the formation of silica phases at a nanometric level.

References: 1. M. Sangermano, G. Malucelli, E. Amerio, A. Priola, E. Billi, G. Rizza, Prog. Org. Coat., 54, 134, 2005. 2. E. Amerio, M. Sangermano, G. Malucelli, A. Priola, B. Voit, Polymer, 46, 11241, 2005.