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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