Morphologies of Multicompartment Micelles Formed by ABC Miktoarm Star Terpolymers

Abstract

Several new multicompartment micellar structures have been identified by cryogenic transmission electron microscopy (cryoTEM) from the aqueous self-assembly of mu-[poly(ethylethylene)][poly(ethylene oxide)][poly(perfluoropropylene oxide)] (mu-EOF) miktoarm star terpolymers. This work extends our previous studies, in which it was found that, upon decreasing the length of the hydrophilic block (O), the resulting micelles evolved from "hamburger" micelles to segmented worms and ultimately to nanostructured bilayers and vesicles. In the terpolymers examined here segmented ribbons and bilayers were found at an intermediate composition between segmented worms and nanostructured bilayers, provided that the fluoropolymer (F) was the minority component in the micelle core. On the other hand, when the F block exceeded the chain length of the hydrocarbon block (E), the superhydrophobic F block imposed a "double frustration" on the self-assembly of the mu-EOF(2-9-5) terpolymer; while F prefers to minimize its interfacial contact with the O corona, it must occupy the majority of the micellar core. Therefore, a richer variety of multicompartment micelles, including well-defined segmented worms, raspberry-like micelles, and multicompartmentalized worms, were formed from one terpolymer, as revealed by cryoTEM. Despite the complexity and variety of the observed aggregate morphologies, a small number of common structural elements can be invoked to interpret the observed micelles and to relate a given structure to the terpolymer composition.