Letter Cite This: ACS Macro Lett. 2017, 6, 1223-1227
pubs.acs.org/macroletters
Temperature-Directed Assembly of Stacked Toroidal Nanorattles Zhongfan Jia, Valentin A. Bobrin, and Michael J. Monteiro* Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane QLD 4072, Australia S Supporting Information *
ABSTRACT: Here, we have developed a new methodology to obtain a pure population of well-defined and new kinetically trapped structures directly in water, inaccessible by other self-assembly techniques. We have exemplified this method through the synthesis of stacked toroidal micelles trapped into a nanorattle with multiple and orthogonal surface chemical functionality. These unique polymer nanorattles result from a water-surrounded inner core (or yolk) of stacked toroidal micelles encapsulated by a shell of stacked toroids. The nanorattles were monodispersed and could be freeze-dried and rehydrated without a change in the nanorattle structure. Confirmation of the kinetically trapped nanorattle structure was through the release of the individual stacked toroids using a plasticizer. Our approach provides a strategy for the synthesis of unique nanostructures that have the potential to be coupled with biological molecules and probes capable of performing multiple tasks and functions.
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One block consists of a thermoresponsive polymer and when the spheres are cooled below its lower critical solution temperature (LCST), the now amphiphilic block copolymers self-assemble within the restricted 3D confined sphere to the nanorattle. This structure is different to the few examples of onion-like nanorattles made through the self-assembly of surfactants,10 amphiphilic dendrimers11,12 or block copolymers13,14 in water. We confirm that the toroidal nanorattles are kinetically trapped by triggering the release of individual toroidal micelles from the nanorattle. Our group developed the temperature directed morphology transformation (TDMT)15−18 method to synthesize a wide range of nanostructures, ranging from spheres, worms, rods, vesicles, donuts, lamellae, and recently tadpoles.18 All these structures could be freeze-dried and rehydrated in water without altering their original nanostructure. Here, we report the synthesis of chemically multifunctional stacked toroid nanorattles directly in water (Scheme 1) at a high weight fraction of polymer (∼10 wt %) and with a narrow particle size distribution. We employ in all emulsion polymerizations a MacroCTA with an adamantane end-group (i.e., MacroCTA2; see Scheme 1). This group not only lowers the LCST to 19 °C (see Figure S5 in SI), but plays an important role in producing a monodisperse particle size distribution during polymerization (see Table 1) due to “superswelling”.19 When heated with the other MacroCTAs to form seed particles stabilized by SDS, the polymerization with styrene (STY) at 70 °C produced low disperse diblock copolymers with monodisperse spherical particles of ∼100 nm in diameter (Dh,DLS) found by dynamic light scattering (DLS). The multifunctional chemical groups
anostructures can be generated with three-dimensional shape and ordering through the assembly of well-defined molecules1,2 and amphiphilic block copolymers3−5 in water. The ability to control these structural features has the potential to produce advanced materials in biological,6 photonics,7 and chemical8 applications. The spontaneous self-assembly of amphiphilic block copolymers (at
