RAFT inverse miniemulsion periphery polymerization in binary solvent mixtures for synthesis of nanocapsules

•Polymeric nanocapsules are prepared via inverse miniemulsion periphery RAFT polymerization.•The hollow particles have aqueous core suitable for delivery of water soluble drugs.•Nature of continuous phase investigated using toluene/hexane mixtures.•Most well-defined nanocapsules obtained using pure toluene as continuous phase.

Herein we report the synthesis of polymeric nanocapsules with an aqueous core via inverse miniemulsion periphery RAFT polymerization (IMEPP) of styrene/divinyl benzene in binary solvent mixtures using an amphiphilic macroRAFT species comprising N-(2-hydroxypropyl) methacrylamide and styrene as dual steric stabilizer and RAFT agent. Inverse miniemulsions were prepared using various ratios of toluene and n-hexane as the continuous phase. For toluene:hexane volume ratios of 100:0–60:40, hollow polymeric nanocapsules were successfully obtained with average diameters generally well below 300 nm. Issues with poor colloidal stability were encountered using toluene:hexane = 50:50. Moreover, the particle size distributions exhibited the greatest uniformity in pure toluene. It is rationalized that the presence of (excessive) amounts of n-hexane in the continuous phase leads to poor steric stabilization of miniemulsion droplets as well as the formation of solid (non-hollow) particles in the continuous phase.

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