Synthesis and application of new core-shell structure via Pickering emulsion polymerization stabilized by graphene oxide

Abstract

Pickering structures significantly improve the compatibility and stability of composite polymer emulsions by virtue of their unique nanoparticle interfaces. An innovative application of Pickering structures to the synthesis of core-shell emulsions is proposed in this paper, two Pickering emulsions containing polystyrene acrylate-polysiloxane core-shell structures stabilized by graphene oxide (GO) were designed. The synthesized Pickering emulsions have excellent dispersibility and physical stability, while its particle size distribution is uniform and below 120 nm. The Pickering structure improves the grafting proportion between the PSA and polysiloxane components to over 87.8%. The GO interface gives the core-shell structure a desirable molecular configuration and high crosslinking degree, facilitating the formation of complete shielding films and stable hydrophobic layer on the cement hydrates. With a contact angle of over 130° and surface energy of below 15 mJ/m2, the capillary water absorption of the concrete decreased by 98.3% with the Pickering emulsions. Meanwhile, the Pickering coatings have the high corrosion potentials under chloride and sulfate attack, weakening the formation of Friedel's salts, gypsum, and ettringite in the cement substrates. Furthermore, the Pickering coating films are resistant to attack by aggressive ions and free radicals under acid/alkaline corrosion and photo-oxidative aging, effectively inhibiting the degradation of polymer molecules and adhesion failure on the cementitious materials.