Interfacial Basicity-Guided Formation of Polydopamine Hollow Capsules in Pristine O/W Emulsions – Toward Understanding of Emulsion Template Roles

In this article, alkane-in-water emulsions have been utilized as templates for polymerization of 3,4-dihydroxyphenylethylamine (dopamine) and l-3,4-dihydroxyphenylalanine (l-dopa). The resulting polymer structures are clearly dependent on the concentration of OH ions, i.e., pH, on the surfaces of the oil droplets, while show little dependence on the electrostatic or hydrophobic interactions between the resulting polymers and the surfaces of the oil droplets. Pristine alkane droplets, stabilized solely by OH ions, have templated formation of hollow capsules due to selective oxidation and self-polymerization of the monomers on the OH ion-rich surfaces of the pristine oil droplets. In contrast, macroporous structures have been obtained when either cationic or anionic surfactants were used to stabilize alkane droplets to lower the concentration of OH ions on the droplet surfaces.