In situ small-angle X-ray scattering studies of sterically-stabilized diblock copolymer nanoparticles formed during polymerization-induced self-assembly in non-polar media

摘要: Reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) is utilized to prepare a series poly(stearyl methacrylate)–poly(benzyl methacrylate) (PSMA–PBzMA) diblock copolymer nano-objects at 90 °C directly in mineral oil. Polymerization-induced self-assembly (PISA) occurs under these conditions, with the resulting nanoparticles exhibiting spherical, worm-like or vesicular morphologies when using relatively short PSMA13 macromolecular agent (macro-CTA), as confirmed by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies. Only kinetically-trapped spherical are obtained longer macro-CTAs (e.g. PSMA18 PSMA31), higher mean degrees (DPs) for PBzMA core-forming block simply producing progressively larger spheres. SAXS used first time monitor various morphological transitions that occur situ during RAFT BzMA targeting either spheres vesicles final morphology. This powerful characterization technique enables evolution particle diameter, aggregation number, number chains per unit surface area (Sagg) distance between adjacent core–shell interface (dint) be monitored function monomer conversion Moreover, gradual morphology PISA unequivocally, approximate ‘lifetimes’ assigned intermediate pure sphere worm PSMA13–PBzMA150 vesicles. Within vesicle phase space, membrane thickness (Tm) increases monotonically DP. Furthermore, combination dynamic light (DLS), TEM post mortem studies indicate lumen volume reduced while overall dimensions remain essentially constant. Thus constrained grow inwards, recently reported an aqueous formulation. suggests universal growth mechanism all formulations.