Asymmetric Polymer Particles with Anisotropic Curvatures by Annealing Polystyrene Microspheres on Poly(vinyl alcohol) Films

Abstract

Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self-assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.

Thermal-Annealing-Induced Self-Stretching: Fabrication of Anisotropic Polymer Particles on Polymer Films

“…From the experimental results, we speculate that the PVA/air interfaces are preferred to be replaced by the PS/air interfaces during the annealing and stretching process. As the PS particles are immersed into the PVA films, the additional interfacial energies between PS and PVA also play a critical role in the morphology transformation, as discussed in our previous work by annealing PS microspheres on PVA films …”

“…PS microspheres and PVA films are chosen as the model materials because of their well known chemical and physical properties and commercial availability. Instead of embedding the PS microspheres in the PVA films, the PS microspheres are spin-coated on the PVA films, giving asymmetric interfaces (air/PS and PS/PVA) for the PS microspheres. − The PS/PVA composite films are bound with metal clips to confine the PVA films on both sides. After thermal annealing in an oven, the PS microspheres sink into the PVA films and are stretched to form anisotropic particles because of the stretching and squeezing forces exerting on the PVA films and the PS particles.…”

Replication of Mesoscale Pore One-dimensional Nanostructures: Surface-induced Phase Separation of Polystyrene/Poly(vinyl alcohol) (PS/PVA) Blends

“…Various transformation and phase separation behaviors of polymer nanomaterials in AAO templates and other atmospheres using chemical solvent and thermal annealing methods have been investigated [22,23,24,25,26,27,28,29,30,31,32,33]. Furthermore, similar polymer phase separations and transformation behaviors at the microscale have also been observed [34,35,36,37,38]. Because of the success of the AAO templating method, many publications have explored various AAO applications such as thermal and physical properties of polymer nanostructures under nanoconfinement conditions, fabrication of higher−order nanostructures, polymerization and crystallization in AAO templates, and the double infiltration nanoencapsulation process [39,40,41,42,43,44,45,46,47,48,49].…”

Polymeric Janus Nanoparticles: Recent Advances in Synthetic Strategies, Materials Properties, and Applications

“…As compared with inorganic materials based Janus system, polymeric Janus particles possess some unique features because of the soft behavior of the polymer backbone and the ease to fine tune the asymmetric structures comparing with inorganic Janus particle. These uniqueness allow for further development of polymeric Janus particles with well‐defined size and controllable physicochemical properties . For instance, in a selected solvent or heating condition, polymeric Janus particles can aggregate into complex superstructures with hierarchical structure .…”