Christopher Henry Such

Control of Particle Morphology in Ab Initio RAFT Mediated Emulsion Polymerization

Recent advances in the use of reversible addition–fragmentation chain transfer (RAFT) polymerization in dispersed phase systems have paved the way for the fine control of the morphology of latex particles that was not possible by conventional free radical polymerization techniques. With this approach, living amphiphilic block copolymers are synthesized that self-assemble to form micelles. The hydrophilic segment is formed from a water-soluble monomer which stabilizes the latex particles as polymerization proceeds and the latex particles grow. The hydrophobic ends of the RAFT diblocks ultimately grow into the polymer that forms the body of the particles. This paper presents examples of ways in which these advances can be used to engineer latex particles with unique morphologies that exhibit specific application properties.

Aqueous Polymeric Hollow Particles as an Opacifier by Emulsion Polymerization Using Macro-RAFT Amphiphiles

A robust polymerization technique that enables the surfactant-free aqueous synthesis of a high solid content latex containing polymeric hollow particles is presented. Uniquely designed amphiphilic macro-reversible addition fragmentation chain transfer (RAFT) copolymers were used as sole stabilizers for monomer emulsification as well as for free-radical emulsion polymerization. The polymerization was found to be under RAFT control, generating various morphologies from spherical particles, wormlike structures to polymer vesicles. The final particles were dominantly polymeric vesicles which had a substantially uniform and continuous polymer layer around a single aqueous filled void. They produced hollow particles once dried and were successfully used as opacifiers to impart opacity into polymer paint films. This method is simple, can be performed in a controllable and reproducible manner, and may be performed using diverse procedures.