Tunable Fluorophobic Effect Determines Nanoparticle Dispersion in Homopolymers and Block Polymers

The controlled placement of nanoparticles (NPs) within homopolymers and block polymers is of broad interest for functional nanomaterials. This manuscript focuses on small molecule-stabilized NPs that bring a large fraction of functionality. For such NP mixtures with block polymers, the overwhelming focus to date has been the use of attractive interactions to localize hydrophilic NPs within the hydrophilic portion of block polymers. Related lipophilic approaches often place NPs at the block polymer interface. Here, a new modality for block polymer-NP control is developed that rather relies upon repulsion via the fluorophobic effect. Fluorinated species strongly associate via repulsion from nonfluorinated media. Here, fluorinated NPs are made with ligand mixtures for granular control over the strength of the fluorophobic effect. Small-angle X-ray scattering data reveal that all F-NPs readily phase separate from polystyrene whereas increasing fluorophobic strength enables dispersions within a fluorinated homopolymer. Next, the F-NP placement within diblock polymers is investigated as a function of the fluorophobic strength. Weakly fluorophobic F-NPs are found predominantly near the diblock interface whereas strongly fluorophobic F-NPs are found to disperse throughout the fluorinated block. The controlled placement of NPs is an emerging way to self-assemble materials.