Polyampholytic hybrid Janus nanoparticles comprising an inorganic silica core and a shell consisting of compartmentalized poly(acrylic acid) and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) grafted polymer chains have been prepared. The synthesis of the nanoparticles was accomplished via a multi-step process commenced by a styrene/methanol Pickering emulsion using amine-functionalized silica nanoparticles (D - 100 nm) as the stabilizer, followed by the free radical polymerization of the styrene droplets to obtain silica nanoparticle stabilized polystyrene colloidosomes. Two different polymers, poly(tert-butyl acrylate) poly(t-BA) and PDMAEMA, were grown from the opposite sides of initiator-modified Janus silica nanoparticles by a two-step surface-initiated atom transfer radical polymerization (ATRP). Following acid hydrolysis of the t-butyl ester groups, the polyampholytic bicomponent particles were obtained. The asymmetric polymer decoration of the silica nanoparticles was verified by scanning electron microscopy, whereas the aqueous solution properties of the hybrid nanoparticles were investigated by potentiometric titration, zeta-potential measurements and dynamic light scattering. Studies on the size of the polyampholytic nanoparticles as a function of the solution pH revealed the presence of individual Janus nanoparticles with a symmetric V-shape change in their size signifying the absence of interparticle aggregation upon ionization of the compartmentalized oppositely charged polyelectrolyte chains. (C) 2017 Elsevier Ltd. All rights reserved.