Colloidal glass formation in polymer nanocomposites

The microstructure of 44 nm diameter silica particles in a polyethylene oxide (PEO) melt are assessed through the experimental measurement of interparticle structure factors S(q,phi). Measurements are made using side bounce ultra small angle x-ray scattering (SBUSAXS) of intermediate to highly filled PEO melts. Results show an increase in the effective particle size by a shift in the first peak of S(q,phi) to lower q when compared to theoretical S(q,phi) based solely on particle volume exclusion. The shift is attributed to an increase in the effective particle size due to adsorbed polymer chains giving a larger excluded volume per particle. Suspension flow properties are observed to obey theories based on volume exclusion when assuming the adsorbed polymer adds 3.1R(g) to the particle diameter. As the particle concentration is increased, a new state appears that displays glassy characteristics.