Anomalous small-angle X-ray scattering characterization of bulk block Copolymer/Nanoparticle composites

We demonstrate the versatility of anomalous small-angle X-ray scattering (ASAXS) to investigate the morphology of bulk multicomponent composites comprising poly (stryrene-b- 2- vinylpyri dine) (PS-PVP) and An nanoparticles. Contrast variation near the L-3 absorption edge of Au enables the separation of the partial scattering functions of the polymer and nanoparticle phases. Theoretical and experimental methodologies developed for our ASAXS analysis of the composites will be useful for the investigation of other such multicomponent systems with heavy elements. This study shows that at 8.8% Au loading the An nanoparticles remain well dispersed in the lamellar polymer matrix, while at 27.0% Au loading the polymer morphology transforms to a hexagonal packed cylinder phase due to the change in the curvature caused by the higher concentration of the dispersed nanoparticles in the PS domain. In the case of 27.0% An nanocomposite we also observe strong concentration fluctuations of nanoparticles in the polymer phase, with a hierarchical structure containing mass fractal aggregates and particle -particle correlation as evidenced by the Q(-2.4) power law scattering in the low Q and a liquid-like peak at the high Q regions of the scattering signal from the nanoparticles.