Abstract
Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as proteins. While there are numerous computer studies, there are few experimental realizations due to a lack of means to produce such colloids with a well-controlled variable Janus balance. Here, we report a simple scalable method to precisely vary the Janus balance over a wide range and selectively functionalize one patch with DNA. We observe, via experiment and simulation, the dynamic formation of diverse superstructures: colloidal micelles, chains, or bilayers, depending on the Janus balance. Flexible dimer chains form through cooperative polymerization while trimer chains form by a two-stage process, first by cooperative polymerization into disordered aggregates followed by condensation into more ordered stiff trimer chains. Introducing substrate binding through depletion catalyzes dimer chains to form nonequilibrium rings that otherwise do not form.
Highlights
Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as proteins
Previous experimental work with hydrophobic patches on otherwise hydrophilic Janus particles suggests that kinetic trapping can select nonequilibrium structures over equilibrium ones, so the ability of structures to anneal and equilibrate can play a role in structure formation
Our experimental and computational observations reveal the dynamical processes that lead to the formation of colloidal chains at different patch ratios, as well as a new dynamical process of surfacecatalyzed ring formation of dimer chains[19,20,21]
Summary
Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as proteins. One of the simplest systems exhibiting complex structures due to chemical heterogeneity is the self-assembly of Janus colloids with one attractive patch, with the rest of the particle being repulsive. The different structures they form depend on the interaction strength ε of the attractive patch and the Janus balance, defined as the fractional area χ of the attractive patch. Our experimental and computational observations reveal the dynamical processes that lead to the formation of colloidal chains at different patch ratios, as well as a new dynamical process of surfacecatalyzed ring formation of dimer chains[19,20,21]
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