Structural effects of TiO2 nanoparticles in photocurable ladder-like polysilsesquioxane nanocomposites

Ladder-like polysilsesquioxanes (LPSQs) are characterized by a double-stranded siloxane backbone, whose chemical and structural properties depend on both the synthesis parameters and the nature of the organic side-chains. In the case of ladder-like (methacryloxypropyl) polysilsesquioxanes (LPMASQ), polymer matrices can be produced by exploiting the presence of photocurable methacrylate groups. Consequently, they can be used to prepare functional nanocomposites (NCs), either by blending with organic polymers such as polybutadiene or exploiting the inorganic fillers' dispersion. Since the properties of LPMASQ-based NCs are strongly related to their structure, the structural changes of polymerized LPMASQ were investigated upon addition of low loadings of TiO2 nanoparticles (up to 3 wt%) by solid state nuclear magnetic resonance and X-ray diffraction. The filler addition leads to the reduction of the polymerization capacity of the LPMASQ organic side-chains. Moreover, a different organization of ladder chains has been highlighted, ascribable to the increase in fully condensed linear ladder units at the expenses of folded chains and defective structures. The methodological approach here adopted can be extended to other composite systems and may help to describe the properties at the filler-matrix interface, offering valuable hints for a better design of these materials.[GRAPHICS].