Amphiphilic
derivatives of fullerene C60 are attractive
from viewpoints of supramolecular chemistry and biomedicine. The establishment
of relationships among the molecular structure, aggregation behavior
and properties such as scavenging radicals of the amphiphilic C60 derivatives is the key to push these carbon nanomaterials
to real applications. In this work, six monosubstituted C60 derivatives were synthesized by a one-step quaternization of their
neutral precursors, which bear Percec monodendrons terminated with
oligo(poly(ethylene oxide)) (o-PEO) chain(s). The main difference
among the C60 derivatives lies in the number and substituted
position of the o-PEO chain(s) within the Percec monodendron. Derivative
with a 4-substitution of the o-PEO chain still showed limited solubility
in water. Other derivatives possessing two or three o-PEO chains exhibited
much improved solubilities and rich aggregation behavior in water.
It was found that the formation of aggregates is regulated both by
the number and the substituted pattern of the o-PEO chains. Typical
morphologies include nanosheets, nanowires, vesicles, nanotubes, and
nanorods. Although the structures of the C60 derivatives
are different from those of traditional surfactants, their aggregation
behavior can be also well explained by applying the theory of critical
packing parameter. Interestingly, the capabilities of the C60 derivatives to scavenge the hydroxyl radicals (OH·
–) followed the same order of their solubility
in water, where the compound bearing three o-PEO chains with a 2,3,4-substitution
got the champion quenching efficiency of ∼97.79% at a concentration
of 0.15 mg·mL–1 (∼0.11 mmol·L–1).