Competitive Self-Assembly Kinetics as a Route To Control the Morphology of Core-Crystalline Cylindrical Micelles

Nucleated self-assembly in selective solvents of core-crystalline block copolymers (BCPs) is a special case of living supramolecular polymerization, leading to rodlike micelles of controlled and uniform length. For the crystallization-driven self-assembly of PFS-containing BCPs (PFS = polyferrocenyldimethylsilane), the formation of block comicelles by sequential addition of different BCPs is well-established. But there are only a few examples of living copolymerization, the simultaneous addition of pairs of BCPs with different corona-forming chains. At present, relatively little is known about the competitive kinetics of different BCPs crystallizing on a common seed. Here we report a systematic study of the competitive seeded growth kinetics of pairs of linear PFS-containing BCPs and show that one can manipulate the kinetics to control the morphology of the comicelles. We found that the seeded-growth kinetics of the individual BCP unimer dominates the coassembly behavior and thus the morphology of the corona. Patchy comicelles with microphase-segregated corona chains are formed when the epitaxial growth rates of the two different BCPs on the common seed are similar. In contrast, factors that lead to dissimilar growth rates (long corona-forming blocks or introduction of charges on corona-forming chains) promote large-scale separation of the corona blocks, leading to block comicelles. Because the termini of the comicelles remain living, they can further direct the growth of unimers, resulting in hierarchical block comicelles with patchy blocks and single-component (homo) blocks. Furthermore, the patchy comicelles can be loaded with either gold or platinum nanoparticles, generating organic-inorganic hybrid materials with potential application in catalysis.