Pickering emulsion polymerization kinetics of styrene: Comparison of bare and surface modified SiO2nanoparticles

Silica-Supported Styrene-Co-Divinylbenzene Pickering Emulsion Polymerization: Tuning Surface Charge and Hydrophobicity by pH and Co-Aid Adsorption

In this work, polymerizations of styrene (St) in the presence of divinylbenzene (DVB) as a crosslinking agent and sodium 4-vinylbenzenesulfonate (VBS) have been performed in Pickering emulsions, using silica nanoparticles (SNps) as stabilizing agents and ammonium persulfate as a hydrophilic initiator. In oil-in-water Pickering emulsions with alkaline continuous phase (pH = 9) at 1, 2, and 3 wt% DVB (relative to St), polydisperse spheroid copolymer submicronic nanoparticles were obtained. Comparatively, polymerizations performed in Pickering emulsions with acidic continuous phase (pH = 5) allowed preparing St-co-DVB microspheres with core–shell structures at 1 wt% DVB and St-co-DVB hybrid monoliths with bi-continuous morphologies at 2 and 3 wt% DVB. It is noteworthy that this work reports Pickering emulsion polymerization as a new strategy for preparing hybrid percolated scaffolds with bi-continuous porosity. The proposed mechanisms originated by pH, DVB, and VBS and the drastic impact caused on the final morphology obtained, either hybrid particles or monoliths, are discussed herein.

Synthesis of cellulose nanocrystals-armored fluorinated polyacrylate latexes via Pickering emulsion polymerization and their film properties

Cellulose nanocrystals-armored fluorinated polyacrylate latex particles with the core-shell spherical shape were prepared by a facile and efficient strategy based on Pickering emulsion polymerization using the modified cellulose nanocrystals, poly(2-(dimethylamino) ethyl methacrylate)-g-cellulose nanocrystal-g-poly(2,2,3,4,4,4-hexafluorobutyl acrylate) (PDMAEMA-g-CNC-g-PHFBA) as a sole Pickering stabilizer. The TEM result indicated that PDMAEMA-g-CNC-g-PHFBA effectively anchored on the outside of latex particles and improved the performance of emulsions, demonstrating the important role of the PDMAEMA-g-CNC-g-PHFBA in the Pickering stabilization process. The influences of the type of Pickering stabilizers and the PDMAEMA-g-CNC-g-PHFBA amount on the emulsion polymerization were investigated. The size of latex particles could be adjusted by PDMAEMA-g-CNC-g- PHFBA amount. XPS result showed that the fluorine-containing groups tended to enrich at the air-film interface of latex film during the heat process, leading to the decrease of surface free energy. The water-oil repellent and mechanical properties of the film could be improved as the content of PDMAEMA-g-CNC-g-PHFBA increased. In addition, thermal analysis showed an enhancement of the thermal properties of latex film upon increasing the PDMAEMA-g-CNC-g-PHFBA content.