Mechanical Stability of Polystyrene and Janus Particle Monolayers at the Air/Water Interface

Abstract

The compressional instability of particle-laden air/water interfaces is investigated with plain and surface-anisotropic (Janus) particles. We hypothesize that the amphiphilic nature of Janus particles leads to both anisotropic particle-particle and particle-interface interactions that can yield particle films with unique collapse mechanisms. Analysis of Langmuir isotherms and microstructural characterization of the homogeneous polystyrene particle films during compression reveal an interfacial buckling instability followed by folding, which is in good agreement with predictions from classical elasticity theory. In contrast, Janus particle films exhibit a different behavior during compression, where the collapse mode occurs through the subduction of the Janus particle film. Our results suggest that particle-laden films comprised of surface-anisotropic particles can be engineered to evolve new material properties.

Collapse mechanisms and extreme deformation of particle-laden interfaces

“…Experiments and simulations show that monolayers of spherocylinders buckle for small aspect ratio of the particles, while flipping of individual particles and bilayer formation is observed for large aspect ratio [57]. For particles with anisotropic surface chemistry, a comparison of homogenous polystyrene particles with gold-polystyrene Janus colloids of the same size reveals that while the homogeneous particles form monolayers that buckle upon compression, the Janus particles form bilayers upon monolayer collapse due to the anisotropic particle-particle and particle-interface interactions [55]. Monolayer collapse can be an undesirable phenomenon in the application of nanoparticle monolayers to advanced functional materials, for instance made from gold nanoparticles [58], or graphene and graphene oxide sheets [59].…”

“…Buckling of planar monolayers of particles has been reported for a variety of systems [50,51,52,53,54,55] and the effective surface tension has often been found to be non-zero at buckling. Monolayers of gold nanoparticles capped with dodecanethiol ligands were found to form local folds and then transition to a trilayer; the wavelength of the wrinkles allowed to extract the bending modulus of the monolayers and trilayers from elasticity theory [53].…”

Assembling semiconducting molecules by covalent attachment to a lamellar crystalline polymer substrate

“…When exceeding a certain packing density, particles jam [ 17 ], which may impede rearrangements. Further compression may not be possible without expelling of nanocrystals from the monolayer [ 18 ] or without buckling of the film [ 19 ].…”

Janus nanoparticles inside polymeric materials: interfacial arrangement toward functional hybrid materials

“…113 Further extensive theoretical simulations and experimental observations indicate that the interfacial activity of the Janus NPs can vary depending on several parameters, including the shape, size, morphology, and distribution of the spatial domains, and that the Janus NPs show an enhanced interfacial activity compared to the corresponding homogeneous particles, regardless of the synthesis and interfacial activity characterization methods. [114][115][116][117][118][119][120][121][122][123][124][125][126][127][128] In analogy to the emulsification of fluid mixtures, Janus NPs are also expected to strongly attach to the interface inside polymer matrices, either in polymer blends or in block copolymers, which will be discussed in sections 3 and 4, respectively. A thorough study of the interfacial behavior of Janus NPs at the fluid-fluid interface is not only essential for further practical application of Janus NPs as solid stabilizers, but also helpful for fundamentally understanding how Janus NPs interact with polymeric interfaces, even though polymer interfaces cannot be simply understood as a fluid-fluid interface.…”