posted on 2020-03-20, 10:29authored byElizabeth Galati, Huachen Tao, Christian Rossner, Ekaterina B. Zhulina, Eugenia Kumacheva
Nanoparticles
(NPs) decorated with topographically or chemically
distinct surface patches are an emerging class of colloidal building
blocks of functional hierarchical materials. Surface segregation of
polymer ligands into pinned micelles offers a strategy for the generation
of patchy NPs with controlled spatial distribution and number of patches.
The thermodynamic nature of this approach poses a question about the
stability of multiple patches on the NP surface, as the lowest energy
state is expected for NPs carrying a single patch. In the present
work, for gold NPs end-grafted with thiol-terminated polymer molecules,
we show that the patchy surface morphology is preserved under conditions
of strong grafting of the thiol groups to the NP surface (i.e., up to a temperature of 40 °C),
although the patch shape changes over time. At higher temperatures
(e.g., at 80 °C), the number
of patches per NP decreases, due to the increased lateral mobility
and coalescence of the patches as well as the ultimate loss of the
polymer ligands due to desorption at enhanced solvent quality. The
experimental results were rationalized theoretically, using a scaling
approach. The results of this work offer insight into the surface
science of patchy nanocolloids and specify the time and temperature
ranges of the applications of patchy NPs.