Anomalous Small-Angle X-ray Scattering Characterization of Bulk Block Copolymer/Nanoparticle Composites

Abstract

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-vinylpyridine) (PS-PVP) and Au 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 Au 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% Au 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.

Analysis of engineered nanomaterials in complex matrices (environment and biota): General considerations and conceptual case studies

“…Anomalous small-angle X-ray scattering uses an X-ray source tuned to just below the absorption energy of the element of interest and thus helps to obtain element-specific information. It has been used to obtain element-specific data in heterogeneous samples containing Ag ENMs but has not been applied extensively to environmental samples containing ENMs [98]. The main issue concerning SAXS is the detection limit; an attractive feature of SAXS is the time-resolved monitoring of the evolution of the structure.…”

Protection of organic carbon in soil microaggregates via restructuring of aggregate porosity and filling of pores with accumulating organic matter

“…We should also point out that the method we are using here is really only another application of the contrast matching technique used extensively in small angle neutron studies to analyze multicomponent systems (Avdeev, 2007) or anomalous small angle X-ray scattering studies (Kirby et al, 2007;Lee et al, 2007;Pranzas et al, 2007); each of these studies employed these routinely applied neutron contrast methods, In analyses of multiphase systems with a complicated small angle scattering profile, the contrast of one phase is changed and the difference in scattering data is attributed to the change in the contrast of that phase. This phase is then analyzed using a two-phase approximation.…”

Anomalous small-angle X-ray scattering from charged soft matter

“…In other studies involving block copolymers, Lee et al [42] performed contrast variation close to the gold L 3 -edge in order to reveal the morphology of bulk block copolymer/inorganic nanoparticle composites. They developed an analysis method to derive the partial scattering functions of the polymer and the nanoparticle phases which could be also suitable for other composite materials.…”