The tough microcapsules of acrylic acid–styrene–isoprene–styrene quadrablock copolymer shell via Pickering emulsion technique

Pickering emulsion technique has been demonstrated a simple method to fabricate the microcapsules. However, the resulted microcapsules are often fragile. This limits their applications. Here, we report that the microcapsules with the nanostructured shell of poly(acrylic acid‐ b ‐styrene‐ b ‐isoprene‐ b ‐styrene) (ASIS), which is of high toughness and elasticity, could be fabricated via Pickering emulsions using ASIS nanoparticles as stabilizing particles. The surfactant‐free ASIS latex (with theoretical molecular weight for each block: 1.5k–15k–55k–10k) was synthesized by reversible additional fragmentation transfer (RAFT) emulsion polymerization using amphiphilic macro‐RAFT agent [poly(acrylic acid) 20 ‐ b ‐polystyrene 5 trithiocarbonate] as both reactive surfactant and polymerization mediator. It was found that the ASIS nanoparticles were able to self‐assemble on oil/water interface to stabilize Pickering emulsion of hexadecane in the pH range from 8 to 12. The droplet diameter was finely tuned from 17 to 5 µm by increasing the ASIS particle levels from 0.13 to 12 wt % based on the mass of the ASIS aqueous dispersions. With toluene as a coalescing aid, the capsules with a coherent and nonporous shell were obtained with the dispersed phase volume percentage as high as 50%. The toluene treated capsules were so mechanically strong to survive the utrasonic treatment. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 46700.