Aliphatic polyurethane-silica nanocomposites prepared by the parallel synthesis: Morphology and mechanical characteristics

Films of aliphatic polyurethane-silica composites containing up to 27.3 mol% of SiO$_2$ nanoparticles have been prepared by the parallel synthesis using the sol-gel technology. It has been revealed that the variations in the mechanical properties of these materials with increasing concentration of nanoparticles exhibit a nontrivial behavior: the ultimate strain gradually increases, whereas the elastic modulus and the yield stress decrease. A correlation of the changes observed in the mechanical characteristics with an increase in the free volume of the material with increasing silica concentration has been established. Atomic-force microscopy has confirmed the existence of a developed system of nanopores with characteristic sizes from 15 to 100 nm in the materials under investigation.