Polarized resonant soft X-ray scattering reveals local chain orientation in polymer-grafted nanoparticles

Polymer-metal nanocomposites that are based on blends of metal NPs and matrix polymers face numerous design limitations and processing challenges. Polymer-grafted nanoparticles (PGNs) are of interest for applications ranging from structural to photonic and electrical. Many of the potential applications (coatings, adhesives, membrane separators, energy storage, etc.) necessitate co-optimization of functional performance with yield stress and toughness. An understanding of how the micro-architecture determines plasticity and failure modes in PGN assemblies is incomplete largely due to lack of tools to fully characterize the microstructure including local interfacial orientation. Here we show the measurement of local chain orientation in a PS-Au PGN system using polarized resonant soft X-ray scattering. The scattering anisotropy was observed at X-ray energies where the anisotropic contrast was affected by the Carbon K-edge 1s-π* resonance of the polystyrene phenyl group. Simple models of the particle geometry with forward simulation of the scattering pattern are consistent with phenyl ring orientation being ‘face on’ relative to the particle.