What are "patchy particles"?
They are simply particles with non-uniform surface compositions
such that particle-particle interactions become directional, allowing
assembly of different types of colloidal crystal structures.
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Applications include:
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* Directed Colloidal Assembly (Photonic Crystals) * Catalysis
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* Interface Stabilizers * Drug Delivery
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Large scale synthesis remains an obstacle since colloidal lithography, where particles are deposited on a surface then modified, produces limited quantities.
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Theoretical simulations predict surface phase separation occurs spontaneously for both small molecule and polymer ligands when the particle size decreases down to the nanoscale, allowing for the bulk synthesis of patchy nanoparticles. In the case of mixed polymer ligands, the following structures are predicted:
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Characterizing nanoscale surface phase separation is a challenge - we recently developed a solid state NMR approach that allows measurement of the domain sizes and morphology.
Guzman-Juarez, B., Abdelaal, A. B., & Reven, L.. NMR Characterization of Nanoscale Surface Patterning in Mixed Ligand Nanoparticles. ACS nano (2022) 16, 20116.
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In the case of mixed polymer ligands, control over the ligand composition is challenging such that most studies have been theoretical, as shown above We overcame this barrier by using a simple exchange method to attach two different types of polymer chains to inorganic nanoparticles with control over a wide range of compositions.
Depending on the ratio of the two polymers, the nanoparticles will assemble into spherical micelles or vesicles upon exposure to a non-solvent for one of the polymers:
Through advanced solid-state NMR, we can characterize the phase separation of the polymer chains on the nanoparticle surfaces for comparison with theoretical predictions.
Current Projects
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Effect of particle size and shape on surface phase separation
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Extend our approach to surface and solid-state assembly to create highly ordered 2D and 3D polymer nanocomposites with different types of nanoparticles and polymers:
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Chen et al. "Hierarchical superstructures assembled by binary hairy nanoparticles."
ACS Macro Letters 5 (2016): 718-723.
