Selective DNP Signal Amplification To Probe Structures of Core–Shell Polymer Hybrid Nanoparticles

An efficient approach for the characterization of core–shell polymer hybrid nanoparticles is presented. Selective signal amplification by dynamic nuclear polarization (DNP) is employed to shed more light on the molecular structure of surface sites and shell of the particles. DNP-enhanced 29Si solid-state NMR is used to clearly prove the core–shell structure of the nanoparticles as well as the success of their functionalization with low amounts of trimethylsiloxy groups. By combination of DNP-enhanced 1H → 29Si and 1H → 13C cross-polarization magic-angle-spinning experiments, differently substituted alkoxysilane moieties, namely, methacryloxypropyltriethoxysilane, 3-methacryloxypropyltriisopropoxysilane, and 3-methacryloxypropyltris(methoxyethoxy)silane, are investigated, revealing various cross-linking capabilities of the particle shell. This knowledge about efficiency of surface functionalization and cross-linking sites strongly influences the application and properties of the core–shell polymer hybrid particles, for instance, as materials for photonic crystals, particle film formation, and coatings. This is of high importance for the design of tailor-made core–shell particle architectures.