A series of pH-responsive methacrylic triblock copolymer vesicles were prepared in water from precursor diblock copolymer vesicles via RAFT seeded emulsion polymerization. More precisely, a poly(glycerol monomethacrylate) macromolecular chain transfer agent (PGMA macro-CTA) was chain-extended with 2-hydroxypropyl methacrylate (HPMA) via RAFT aqueous dispersion polymerization to prepare a large batch of PGMA-PHPMA diblock copolymer vesicles. Aliquots of these PGMA-PHPMA vesicles were subsequently chain-extended using varying amounts of 2-(diisopropylamino)ethyl methacrylate (DPA) via RAFT seeded emulsion polymerization to prepare a series of PGMA58-PHPMA300-PDPAXtriblock copolymers, where x was systematically varied from 86 to 460. As far as we are aware, this is only the second report of pH-responsive nanoparticles to be prepared by polymerization-induced self-assembly (PISA). Microphase separation between the two membrane-forming blocks produces vesicles with a distinctive framboidal morphology (see Figure below), whose surface roughness increases when targeting higher x values. TEM, DLS and SAXS studies confirm that these framboidal vesicles remain intact at neutral pH, but undergo irreversible dissociation on addition of acid. At neutral pH, the vesicles have a mean hydrodynamic diameter of around 400 nm and possess anionic character. At low pH, protonation of the tertiary amine groups leads to vesicular dissociation: the particle diameter is dramatically reduced (see Figure below) and aqueous electrophoresis indicates cationic character for the ill-defined colloidal remnants.

pH-responsive framboidal vesicles prepared using polymerization-induced self-assembly via RAFT aqueous dispersion polymerization

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.