Rational design and synthesis of transition layer-mediated structured latex particles with poly(vinyl acetate) cores and poly(styrene) shells

The synthesis of structured latex particles containing hydrophilic poly(vinyl acetate) (PVAc) cores and hydrophobic poly(styrene) (PS) shells mediated by a controllable transition layer was reported. A transition layer was fabricated onto PVAc cores by introducing a coupling monomer and butyl acrylate (BA), prior to polymerization of second-stage St-based monomer mixture. While such structured PVAc/PS latex particle obtained was thermodynamic non-equilibrium, straightforward synthetic route of the transition layer can be optimized so that the particle morphology is kinetically achievable. Analysis by transmission electron microscopy shows that the particle morphology is highly influenced by both the transition layer composition and PS-based polymer composition. Two-phase particle morphology without transition layer was an inverted acorn-like structure with single PS core wrapped by PVAc shells. The particle morphology mediated by transition layer varied from that of a broken egg shell-like structure with PS-based coating, over intermediate structures in which uniform PS protuberances surrounded PVAc cores, to core/shell structure with single PVAc core. This general approach may offer a number of possibilities for design and synthesis of kinetically controllable phase-separation morphologies for a variety of applications.