SAXS and TEM investigations on thermoplastic nanocomposites containing functionalized silica nanoparticles

Transmission electron microscopy (TEM) and small angle X-ray scattering (SA XS) were used to characterize the morphology of thermoplastic nanocomposite s. These materials were based on a thermoplastic matrix of a copolymer of m ethylmethacrylate (MMA) and 2-hydroxyethylmethacrylate (HEMA) with spherica l 10 nm silica particles as a filler (filler content 2, 5 and 10 vol%, resp ectively). Depending on the surface modification of the particles, it was p ossible to control the aggregation tendency of the primary filler particles . With uncoated particles large aggregates about 100 nm in size could be ob served by TEM. For nanocomposites containing particles coated with methacry loxypropyltrimethoxysilane (MPTS), TEM showed that the particles were bette r dispersed in the polymer matrix only forming aggregates comprised of two or three primary particles. In comparison to the TEM results, the volume we ighted particle size distribution calculated from SAXS for the systems with uncoated particles is monomodal and shows particle sizes in the range of p rimary particles whereas the systems with MPTS coated particles revealed a bimodal size distribution with particle sizes comparable to those measured with TEM. To obtain complete information about the morphology of the nanoco mposites above the critical upper limit of detectable scattering vectors (p article sizes >50 nm) SAXS has to be supported by TEM, whereas in the nanos ize range below the critical limit both methods exhibit an excellent corres pondence.