Probing the Heteroepitaxial Seeded Growth and Self-Sorting Processes of Segmented Co-Micelles with Chemically Distinct Crystalline Cores

Abstract

The ability to produce uniform micellar nanoparticles with controlled dimension and spatially controlled functionality is a key challenge in nanoscience. Living crystallization-driven self-assembly (CDSA) of block copolymers (BCP) has emerged as an effective approach to generate uniform size-tunable core-shell micellar nanoparticles; however, most core-shell micelles generated via CDSA consist of a continuous crystalline core from BCPs with the same core-forming block. Herein, we perform insightful studies of heteroepitaxial CDSA process from chemical distinct core-forming poly(ferrocenyldimethylgermane) (PFDMG) and poly(ferrocenyldimethylsilane) (PFDMS) based BCPs to produce segmented block comicelles. The heteroepitaxial growth process produced micelles with kinetically trapped crystalline cores that are thermodynamically less stable than the materials formed via spontaneous nucleation. This was rationalized by determining the previously unknown core lattice of PFDMG micelles, self-assembly experiments, and theoretical lattice energy calculations, providing an insight into the energetic penalty associated with heteroepitaxial growth. These methods for determining the theoretical core lattice energies in these BCP systems could provide a way to screen BCP candidates that can undergo heteroepitaxial growth. Furthermore, by using our newfound understanding of these micelle systems, we achieved the formation of micelles with crystalline cores that undergo self-sorting, driven by self-seeding from fragmented triblock comicellar structures.