Pickering emulsions stabilized by metal-organic frameworks, graphitic carbon nitride and graphene oxide

Investigation of Composite Protective Coatings Coregulated by Core-Shell Structures and Graphene Oxide Interfaces

The construction of multiple microstructures is a significant measure in improving the protective performance of composite polymer coatings. In this paper, a novel polystyrene acrylate-highly hydrophobic polysiloxane composite emulsion was fabricated by innovatively integrating the core-shell emulsion method and Pickering emulsion method through the interfacial stabilization and molecular polymerization regulation of graphene oxide, achieving a significant improvement in the compatibility of the thermoplastic core with a thermoset shell. The bonding degree between the polystyrene acrylate (PSA) component and the siloxane component is significantly improved in the synthesized composite emulsions, achieving the dual protection of the cementitious substrate with surface shielding and internal crystalline hydrophobicity. The capillary water absorption of the concrete treated with Pickering emulsions is reduced by over 98.3% with high hydrophobicity and low permeability. Meanwhile, the absolute ζ-potential and impedance of composite membranes reach over 45 mV and 10⁹ ohms, respectively, giving the cementitious substrate excellent resistance to ionic attack and acid/alkaline corrosion. In addition, the composite membranes have excellent resistance to tensile cracking and physical erosion, maintaining a favorable adhesion level and plastic deformation under acid/alkaline attack and thermal aging, respectively.

Pickering Emulsions Stabilized by Mesoporous Nanoparticles with Different Morphologies in Combination with DTAB

The morphology of nanoparticles plays a significant role in the properties and applications of Pickering emulsions. Oil-in-water (O/W) Pickering emulsions were prepared using spherical, rod-like, and thread-like mesoporous silica nanoparticles (MSNPs) in combination with the cationic surfactant dodecyltrimethylammonium bromide (DTAB) as a stabilizer. The effects of nanoparticle morphology on the stability and stimuli-responsive properties of Pickering emulsions were investigated. For spherical and rod-like MSNP systems, stable Pickering emulsions were obtained at DTAB concentrations above 0.2 mmol·L^-1. Stable Pickering emulsions containing thread-like MSNPs were produced at lower DTAB concentrations of approximately 0.1 mmol·L^-1. The droplets with thread-like MSNPs were extremely large with an average diameter around 700 μm at DTAB concentrations of 0.1-0.3 mmol·L^-1, which were approximately 20 times larger than those of conventional droplets. Scanning electron microscopy (SEM) images showed that all three types of MSNPs were located at the O/W interfaces. Irrespective of the morphology of the MSNPs, all the stable Pickering emulsions retained their original appearance for more than 6 months. By adding NaOH and HCl alternatively, the Pickering emulsions containing spherical and rod-like MSNPs could be switched between unstable and stable states more than 60 times. The Pickering emulsions containing thread-like MSNPs, by contrast, could have their droplet size switched between large and small more than 10 times without any obvious phase separation. The high anisotropy of thread-like MSNPs contributed to the low interface curvature of the droplets. This study revealed the relationship between the morphology of MSNPs and the characteristics of Pickering emulsions. These results enrich our knowledge about the formulation of Pickering emulsions and expand their applications.