(490a) Impact of Janus Particle Amphiphilicity on the Rheological Properties of the Air/Water Interface

Studies on nanoparticles with anisotropic surface properties, i.e., Janus particles, have gained significant attention due to the possibility of novel applications such as assembling functional structures, design of active nanomotors, and biological sensing and imaging. Janus particles are also of interest for interfacial applications, as they can bind to interfaces stronger than homogeneous particles and their surfaces can be tuned to serve added functionalities. Interfaces can be subjected to deformations that produce compression/expansion and shear stresses. Therefore, it is important to understand the impact that the Janus character brings to interfaces. Specifically, the characteristics of both faces are important as those control how the particles are interacting at the interface, which ultimately affects the resulting interfacial microstructure. In addition to nanoparticles, surfactants can be also present in the solution, which adds to the complexity of interfacial interactions. In this study, we fabricated 1μm Janus particles with a hydrophilic silica core and a thin (10nm thick) gold cap. The particles are further modified with different thiols to achieve a varying degree of Janus amphiphilicity. We analyze the impact of the Janus degree of amphiphilicity on the interparticle interactions at the air/water interface, and the response of such particle-laden interfaces to applied stresses. Furthermore, we look into how the presence of anionic surfactants (sodium dodecyl sulfate) on the water phase affects the behavior observed. Our results show that by controlling the degree of amphiphilicity, one can drastically change the resulting microstructure, which in turn affects the response to different stresses.