Acheiving highly ordered nanoparticle structures in polymer solution without chemical grafting

Nanoparticle arrays with highly ordered structures have drawn great attention based on their potentials to improve the physical properties compared to the randomly oriented structures. However, it is often difficult to disperse nanoparticles in order in a neat polymer matrix keeping the liquid-like processability, thus requiring complicated and time expensive laborious procedures. In this work, we report that nanoparticles can be highly ordered by simply dispersing them in poly(ethylene glycol) derivative solution. Without chemical grafting, the strong hydrogen bonding between nanoparticles and the PEG complex could retain the superstructures in the liquid-phase with excess amount of water. The systematic investigation is carried out by varying molecular weight/concentration of polymers/nanoparticles and temperature with small-angle X-ray scattering and oscillatory rheometry experiments.