Temperature‐Directed Formation of Anisotropic Kettlebell and Tadpole Nanostructures in the Absence of a Swelling‐Induced Solvent

• Published in: Angewandte Chemie 2022-03, Vol.134 (11), p.n/a
• Main Authors: Chen, Sung‐Po R., Bobrin, Valentin A., Jia, Zhongfan, Monteiro, Michael J.
• Format: Article
• Language: English
• Subjects: Anisotropic Nanoparticles; Anisotropy; Asymmetric Structures; Chemistry; Emulsion Polymerization; Glass transition temperature; Juveniles; Nanoparticles; Polymers; RAFT Polymerization; Solvents; Swelling; TDMT; Transition temperatures
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202113974

Anisotropic Janus (“snowman”) nanoparticles with a single protrusion are currently made via the solvent swelling‐induced method. Here, we demonstrate without the aid of toxic solvents a generally applicable method for the formation of anisotropic polymer nanoparticles directly in water by controlling polymer mobility through tuning its glass transition temperature (Tg). Spherical structures, formed immediately after the emulsion polymerization, transformed into uniform tadpoles (with head diameter ≈60 nm and tail length ≈130 nm) through the protrusion of a single cylindrical tail when cooled to a temperature above the Tg of the polymer. Cooling the spheres to below the Tg produced kinetically trapped kettlebell structures that could be freeze‐dried and rehydrated without any structural change. These unique kettlebells could transform into uniform tadpoles by heating above the Tg, representing a triggered and on‐demand structural reorganization. Anisotropic kettlebell and tadpole polymer nanostructures formed through a single protrusion from spheres. This method obviates the commonly used solvent swelling‐induced method to form anisotropic particles by driving tail assembly through enhanced chain mobility by tuning the glass transition temperature of the polymer core. Further, the kettlebells could be isolated and transformed to tadpoles on‐demand with temperature.