“Janus particles” are defined by controllable topological and chemical anisotropy. In their study, Shutao WANG and colleagues chose a typical oil-in-water emulsion system, styrene (St) and divinyl benzene (DVB) in water emulsion, into which hydrophilic monomer (such as, acrylic acid (AA) or acrylamide (AM) et al. ) were introduced as anchoring molecules. The polymerization was initially designed to occur inside the oil droplet. It turned out, however,
that a particle nucleus produced inside of oil droplts would move toward the oil/water interface. As a result, the hydrophilic anchoring monomers in the external water phase could contact the particle nucleus and be initiated to polymerize, triggering interfacial anchoring polymerization.  Thus, preferential copolymerization of AA, St and DVB occurred along the interface in two directions, resulting in the formation of crescent-moon shaped Janus particles.

CAS news release, June 28, 2017