Sunday, April 10, 2016

Superlattices Patterned by Polymers

Scientists have shown that self-assembled superlattices, made up of nanoparticles with polymer chains grafted onto their surfaces (“hairy nanoparticles,” or polymer “brushes”), can be tailored to exhibit desired characteristics for applications ranging from nano- to biotechnology. Such multicomponent polymer-nanoparticle composites represent an important class of materials that exhibit emergent properties arising from their mesoscale structure.
The use of extended polymeric ligands on the nanoparticles’ surfaces (as opposed to the shorter ligands native to the nanoparticles) offers distinct advantages, as they allow for precise tuning of the effective size of the composite particles and of the “softness” of the interactions between them through changes in the polymer’s molecular weight, chemical nature, architecture, stiffness, and solvent.
With the help of grazing-incidence small-angle x-ray scattering (GISAXS) measurements at Beamline 7.3.3, the scientists developed a set of modular building blocks—the aforementioned polymer-grafted nanocrystals—in which the inorganic core and the organic ligand shell play complementary and equally important roles in dictating the structure and function of the final assembled phase.
They demonstrated the formation of a diverse array of self-assembled binary superlattices with both two- and three-dimensional ordering. The study will open up new and exciting opportunities for the bottom-up design of functional inorganic-organic hybrid materials with controlled nanoscale interfaces and mesoscale ordering.
Scanning electron microscopy image (left) and GISAXS pattern of AB-type two-dimensional superlattices (right). 
Left inset: Schematic illustration of nanoparticles end-grafted with polymer brushes.

Work performed at Beamline 7.3.3.
Xingchen Ye, Chenhui Zhu, Peter Ercius, Shilpa N. Raja, BoH, Matthew R. Jones, Matthew R. Hauwiller, Yi Liu, Ting Xu, and A. Paul Alivisatos, “Structural diversity in binary superlattices self-assembled from polymer-grafted nanocrystals," Nature Communications 6, 10052 (2015).

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