Defined micelles: A completely uniform and structurally precise micelle spontaneously formed by exactly seven amphiphilic dendro‐calixarene molecules in aqueous solution has been determined by cryo‐TEM and 3D reconstruction techniques. The picture shows seven calixarene head groups, which have been fit visually into the reconstructed density map of the micelle.
Exactly eight amphiphilic fullerene dendrimer molecules form a globular micelle spontaneously in aqueous solution. This supramolecular organization can be turned on and off by an external stimulus (pH). Owing to the remarkable structure persistence of the micelles, their three‐dimensional structure could be determined from cryogenic transmission electron micrographic images and the molecular architecture was subsequently modeled (see picture).
Bolaamphiphiles (“bolas”) containing two secondary amide groups at the ends of an oligomethylene
chain and two amino acid type headgroups were synthesized. The structures of crystals, of noncovalent
fibers, and of surface monolayers on gold strongly depended on odd−even effects. In the crystal structures
of alanine−alanine dipeptides with C11- and C12-α,ω-amino acid linkers, helical (even number of methylene
groups in the chain) or sheetlike (odd) arrangements of the headgroups were found. Bolas containing two
different amino acid end groups, namely, d- or l-alanine and l-lysine, connected by the same C11- and C12
linkers did not crystallize. Only the even-numbered bolas gave fibers. l- and d- configurations of alanine
headgroups affected the curvature of the fibers. Diamido bolas with terminal SH-groups self-assembled
on gold. Only those with even-numbered chains gave rigid monolayers. Simple stereochemical arguments
concerning the fitting of amide hydrogen bond chains on both ends of the bolas are given to explain the
observed differences in crystals, fibers, and monolayers.
A new class of non‐ionic dendronized multiamphiphilic polymers is prepared from a biodegradable (AB)n‐type diblock polymer synthesized from 2‐azido‐1,3‐propanediol (azido glycerol) and polyethylene glycol (PEG)‐600 diethylester using Novozym‐435 (Candida antarctica lipase) as a biocatalyst, following a well‐established biocatalytic route. These polymers are functionalized with dendritic polyglycerols (G1 and G2) and octadecyl chains in different functionalization levels via click chemistry to generate dendronized multiamphiphilic polymers. Surface tension measurements and dynamic light scattering studies reveal that all of the multiamphiphilic polymers spontaneously self‐assemble in aqueous solution. Cryogenic transmission electron microscopy further proves the formation of multiamphiphiles towards monodisperse spherical micelles of about 7–9 nm in diameter. The evidence from UV–vis and fluorescence spectroscopy suggests the effective solubilization of hydrophobic guests like pyrene and 1‐anilinonaphthalene‐8‐sulfonic acid within the hydrophobic core of the micelles. These results demonstrate the potential of these dendronized multiamphiphilic polymers for the development of prospective drug delivery systems for the solubilization of poorly water soluble drugs.
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