| The formation of mobile and surface-bound electric charges in aqueous environments has been widely studied; by contrast, charge formation in nonpolar media is far from understood. The existence of charged mobile species and significant surface charging in nonpolar solutions of ionic surfactants are well documented, but there is no consensus about the mechanisms of charging, and very few studies acknowledge that even nonionic, non-dissociable surfactants can promote charging in nonpolar liquids. The present work primarily aims at expanding our understanding of surfactant mediated electric charging in nonpolar liquids. This task is approached by comparing the electrostatic effects of an ionic and nonionic surfactant that form very similar micelles. The surfactants’ ability to raise the conductivity in low dielectric media is analyzed first. Next, the tendency of both types of surfactants to impart surface charges on polymer particles in nonpolar liquids is studied by electrophoresis for particles of different material and surface functionalization. Independent evidence both for particle charging and for the formation of screening ions in solution is obtained by analyzing the pair interaction energy of suspended polymer particles. The results of this study provide valuable clues about the mechanisms of charge separation in the nonpolar liquid bulk and on particle surfacesat surfactant concentrations above and below the critical micelle concentration.;Besides the fundamental understanding the charging phenomena in nonpolar oils associated with surfactants, self-assembled spherical reverse micelles are described as a novel tool to synthesize nano-sized hydrogel particles, highly crosslinked networks of water-soluble polymers. In order to achieve good reproducibility and particle size control, the hydrophilic cores of reverse micelles/microemulsions are utilized as templates for the polymerization process. More excitingly, copper-free Click chemistry is introduced in synthesizing nanogels templated by swollen reverse micelles. This nanogel synthesis allows for even better control of the particle size while avoiding metal catalysts and free radicals that are considered hazardous for most biomedical applications. |
