(133f) Nanocomposites with Enhanced Mechanical Properties Through Optimized Particle-Polymer Interface and Processing

The embedding of nanoparticle fillers into a polymer matrix facilitates an enhancement of mechanical or optical properties as well as the introduction of novel functions, even when only small amounts of fillers are introduced. The fabrication of such nanocomposites however involves more than just mixing the two components, but needs to be carefully planned and studied. Whilst many applications demand for a homogeneous distribution of nanoparticles in the matrix, due to their high specific surface area they tend to instantly agglomerate when mixed with polymers.
In this paper, we present the fabrication of optically transparent nanocomposites with enhanced mechanical properties. Thereby, it is a prerequisite to have a highly homogeneous distribution of the nanoparticles in the matrix, without any significant agglomeration. This is achieved using metal oxide nanoparticles with sizes below 10 nm that are subjected to a controlled chemical modification using small organic molecules (with molecular mass < 350 g/mol). Through this surface modification, highly stable and concentrated nanoparticle dispersions could be obtained, which were then used for the preparation of nanocomposites by mixing with epoxy resins. The effect of different types of surface modification on the mechanical and optical properties of the fabricated nanocomposites was investigated. It is shown that the physical and chemical interactions within the particle-polymer interface and thus the mechanical properties could be varied by employing different ligands. Additionally, the influence of different ways of processing is presented, showing that optimum properties were only achieved after an additional step to remove excess organics from the nanoparticle surface. Different analytical techniques such as IR and NMR spectroscopy and small-angle X-ray scattering (SAXS) were utilized for characterization.