Combined Emulsion and Phase Inversion Techniques for the Preparation of Catalytic PVDF Microcapsules

Formation of superhydrophobic microspheres of poly(vinylidene fluoride- hexafluoropropylene)/graphene composite via gelation

We report on the spontaneous formation of superhydrophobic poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)/graphene composite microspheres with uniform size via gelation. When the suspension of PVDF-HFP/graphene (0.25 wt. % with respect to PVDF-HFP) in DMF adsorbs water vapor, it changes to a hybrid gel. A dried porous gel is obtained after solvent exchange and freeze drying. Morphology characterization shows that this hybrid gel is composed of PVDF-HFP/graphene microspheres with a diameter of 8-10 μm. In contrast, PVDF-HFP solution gives rise to a cellular microstructure following the same experimental procedures. We further elucidate the formation mechanism on the basis of the characterization by freeze fracture transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry characterizations. Furthermore, contact angle measurements of water on PVDF-HFP/graphene indicates that the hydrophobic nature of PVDF-HFP combined with the micro/nanoscale hierarchical texture creates a superhydrophobic surface. Such superhydrophobic microspheres may have potential applications as water-repellent catalyst-supporting materials.

Formation and size tuning of colloidal microcapsules via host-guest molecular recognition at the liquid-liquid interface

Stimuli-responsive colloidal microcapsules have been fabricated at the oil-water interface using molecular recognition between functionalized gold nanoparticles. Water-soluble beta-cyclodextrin-capped gold nanoparticles and organo-soluble adamantyl-functionalized gold nanoparticles are self-assembled at the water-toluene interface via specific host-guest molecular interactions to provide robust microcapsules. Multivalent interactions of complementary ligands on the nanoparticle surface provide stability to these capsules. Unlike covalently cross-linked microcapsules, the reversible nature of these bridging interactions can be used to manipulate the size of these capsules via introduction of competing adamantane containing amphiphilic guest molecules. Partial disruption of interfacial cross-linking allows microcapsules to coalesce with each other to form larger capsules.