Spontaneous phase separation has been detected in mixed ligand shells of nanoparticles for both low molecular weight and polymeric ligands. Although there is growing interest in such “patchy nanoparticles”, the majority of the studies have been theoretical rather than experimental due to difficulties in preparing significant quantities of nanoparticles with controlled ligand compositions. [1] Experimental validation has also lagged to due to the lack of appropriate tools to detect nanoscale phase separation. Here we apply NMR methods developed for characterizing heterogeneities in complex materials on different length scales to nanoparticles with polymer and low molecular weight mixed ligand shells. The mixed ligand shells consisted of different ratios of aromatic (polystyrene or phenyl) and aliphatic (polyethylene oxide or dodecyl) phosphonic acids on 4 nm ZrO2 nanoparticles. The results for 1H NOESY, 1H double quantum MAS, 1H spin diffusion and 1H-13C HETCOR NMR experiments on the nanoparticles with polymer versus small molecule ligand shells were compared. In the case of the low molecular weight mixed ligand shells, model systems consisting of Janus particles or physical mixtures of nanoparticles functionalized with only one ligand were studied to calibrate the 1H spin diffusion experiments originally developed for polymeric materials.

Detection of nanoscale phase separation in nanoparticles with mixed ligand shells

255th National Meeting (2018)

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