Controlled Fabrication of Uniform Digital Nanorods from Precise Sequence-Defined Amphiphilic Polymers in Aqueous Media

Compared with spherical micelles, rod/worm-like micelles not only have extended blood circulation duration, but also exhibit favorable cellular uptake behavior, which is promising for next-generation nanomedicine and biomaterials. However, the controllable fabrication of narrowly dispersed nanorods in aqueous media is still challenging. Herein, the methodology of thermal annealing was developed for the fabrication of helical nanorods as well as a series of nanorods with different lengths. The thermal annealing process generally consisted of adding a percentage of organic solvent (10%(V/V) or 20%(V/V)) to the digital micellar aqueous dispersion, followed by heating at 90 °C for 1 h, then cooling naturally to room temperature, and dialyzing against water to remove the organic solvent. Right-handed helical nanorods were afforded by the treatment of 45 nm digital micelles in the presence of 10%(V/V) dioxane, while left-handed helical nanorods were obtained in the presence of 20%(V/V) dioxane. Meanwhile, the controlled growth of rod-like digital micelles was achieved after thermal annealing in the presence of different types of organic solvents, and the length of the annealed nanorods was correlated with the types of organic solvent. Furthermore, no matter the size of initial digital micelles, they all exhibited similar trend of rod growth in the presence of a certain amount of organic solvent, allowing for controllable formulation of narrowly dispersed nanorods. In addition, supramolecular self-assembly by amphiphilic dendritic oligourethane readily fabricated diverse uniform nanorods in aqueous media. Overall, this work provided an attractive methodology to fabricate uniform digital nanorods.