Reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of methacrylic monomers in a suitable solvent enables the in situ synthesis of diblock copolymer spheres, worms or vesicles. Polymerization-induced self-assembly (PISA) occurs when using a soluble macromolecular chain transfer agent (macro-CTA) to polymerize a miscible monomer to produce an insoluble second block, thus forming sterically-stabilized diblock copolymer nanoparticles. For a given copolymer, the final morphology is dictated by various parameters, including the mean degree of polymerization (DP) of the stabilizer block, the target DP for the core-forming block and the copolymer concentration. PISA syntheses have been studied using in situ small-angle X-ray scattering (SAXS), which has provided direct evidence for the evolution in copolymer morphology. In the present work, poly(stearyl methacrylate)31-poly(benzyl methacrylate)2000 (PSMA31-PBzMA2000) nanoparticles are targeted in mineral oil. Remarkably, the nascent particles that are formed during the micellar nucleation event are non-spherical (see Figure 1), even though the final copolymer morphology obtained at full conversion comprises well-defined spheres. Similar non-spherical nuclei have been observed for other PISA formulations, suggesting that these findings may be generic.

Time-resolved small-angle x-ray scattering studies of the micellar nucleation event during polymerization-induced self-assembly

253rd National Meeting (2017)

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