Determination of Nucleation Process and Spherical Micelle Growth by Time‐Resolved SAXS During PISA: Evidence from Liquid Crystalline Spherical Nanoparticles

ABSTRACT Polymerization‐induced self‐assembly (PISA) has emerged as a versatile and scalable approach for producing block copolymer nanoparticles with precisely controlled, narrow size distributions. However, the mechanism by which PISA via reversible addition–fragmentation chain transfer (RAFT) polymerization achieves narrow particle size distributions despite potentially broad polymer molecular weight distributions remains unclear, likely reflecting the influence of its process control. Time‐resolved small‐angle X‐ray scattering (TR‐SAXS) provides a means to monitor PISA in real‐time. In this study, PISA was applied to the synthesis of liquid crystalline spherical micelles, allowing detailed observation of nucleation and particle growth. Variations in the macromolecular chain transfer agent (macro‐CTA) concentration modulated early‐stage reaction conditions, influencing the structural evolution of the core‐forming block in pre‐existing nuclei from interdigitated to partially and fully non‐interdigitated conformations. These findings advance the mechanistic understanding of process control in PISA for potential applications including but not limited in optical and biological fields, particularly with respect to nucleation and particle growth.