Molecularly Controlled Coagulation of Carboxyl-Functionalized Nanoparticles Prepared by Surfactant-Free Miniemulsion Polymerization

Abstract

We present the synthesis of molecularly controlled “CO₂-switchable” polystyrene nanoparticles by surfactant-free miniemulsion polymerization using a carboxyl-functionalized surface-active monomer, which acts as comonomer and stabilizer at the same time. The obtained nanoparticles are about 100 nm in size and show a small size distribution, confirmed by dynamic light scattering (DLS) and electron microscopy. Under ambient conditions, the latex particles form a stable suspension that can be coagulated by bubbling CO₂. The redispersion of the coagulated particles can be easily achieved by ultrasonication. The reversibility of the coagulation is confirmed after several coagulation/redispersion cycles (CO₂ bubbling and ultrasonification) from DLS and zeta potential measurements