Figure 1.

TEM images obtained for PMAA₅₆–PHBMA_y diblock copolymer nanoparticles prepared at 20% w/w solids via RAFT aqueous emulsion polymerization at 70 °C. Polymerization-induced self-assembly (PISA) leads to the formation of small spherical nanoparticles for (a) PMAA₅₆–PHBMA₅₀ and (b) PMAA₅₆–PHBMA₁₃₀. Synthesis of (c) PMAA₅₆–PHBMA₁₅₀ produces a distinctive “monkey nut” morphology. However, targeting a mean degree of polymerization for the PHBMA block of either (d) 300 or (e) 1000 only leads to the formation of relatively large spheres. (f) PISA syntheses conducted using a purified batch of HBMA monomer also produce a “monkey nut” morphology when targeting PMAA₅₆–PHBMA₁₅₀, clearly indicating that this unusual morphology is not simply the result of in situ cross-linking as a result of the dimethacrylate impurity in the HBMA monomer.