Abstract
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.
Highlights
The bare Ludox CL silica nanoparticles (SNps) are characterized by the presence of aluminol groups on their surface, conferring them a positive charge of about +44 mV and 47.8 mV at pH = 4.5 and 3.5, respectively [48,50]
As soon as VBS was added to the water phase at pH = 5, it adsorbed onto the nanoparticles’ surface via its anionic sulfonate group through electrostatic interactions, inducing a variation in the SNps’ hydrophilicity
It can react with the other monomers, due to its vinyl group, and on the other hand, it adsorbs onto the cationic silica nanoparticles
Summary
Great industrial and academic interests are focused on the design of hybrid nanocomposite materials because they exhibit fascinating properties when inorganic and organic nascent compounds are ingeniously combined [1,2,3,4,5]. These hybrid materials can be engineered in such a way that could bring about electrical, optical, magnetic, or mechanical properties [6,7,8,9] while displaying various morphologies, including spherical, raspberry-like, snowman-like, or hollow microspheres [10,11,12,13]. These materials are successfully used in diverse application fields such as electronics, optics, biomedicine, catalysis, cosmetics, adsorption, and separation processes [14,15,16]
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