Fig. 3
Mechanism of the hierarchically axial growth of the micelles. After neutralizing the aqueous solution and removing the by-products before dialysis, all the samples are prepared from the neutralized aqueous solution unless otherwise noted. a TEM images showing the self-assembled evolution of POSS-SS-(PEG)8 with the concentration of 1 mg/mL in pH 8 solutions for various times. Insets are the correspondingly schematic structures. b AFM and c Cryo-TEM images of the short cylindrical formations at 2 h. Scale bars: 50 nm. d DLS results of the nanoparticles for various times. e The possible self-assembled mechanism of nanostructural axial growth. In this process, the thiol–disulfide exchange reaction makes the disperse unimolecules quickly aggregate and interlink by the disulfides, thus forming many oligomer-linked cylinders from the pre-micelles with the hierarchical self-assembly behaviors. The low kinetic barrier at both ends, due to the steric hindrance areas from POSS-embedded domains and the swollen layers from stretched PEG shells, furnishes these cylinders with higher reactive points at the micellar ends and drives the subunits to connect together. The orange cube represents the POSS core, the red ellipsoid represents the disulfide linkage and the cyan chain represents the PEG shell
