Introducing Chirality into Nonionic Dendritic Amphiphiles and Studying Their Supramolecular Assembly

Abstract

Chiral head groups have been introduced into water-soluble hydroxyl-terminated nonionic amphiphiles and the impact of the head group stereochemistry on the supramolecular ultrastructures has been studied. Enantiomeric isomers were compared with the achiral meso form and the racemic mixture by means of cryogenic transmission electron microscopy and circular dichroism spectroscopy. Structurally, all amphiphiles are composed of the first-generation hydrophilic polyglycerol head group coupled to a single hydrophobic hexadecyl chain through an amide linkage and diaromatic spacer. The enantiomers aggregate to form twisted ribbons with uniform handedness, whereas the meso stereoisomer and racemic mixture produce elongated assemblies, namely, tubules and platelets, but without a chiral ultrastructure. Simulations on the molecular packing geometries of the stereoisomers indicate different preferential assembly routes that explain the individual supramolecular aggregation behavior.

Controlled self-assembly of stomatosomes by use of single-component fluorinated dendritic amphiphiles

“…In fact, in the absence of fluorinated tail segments, i.e. for the related dendritic amphiphiles with pure alkyl tails as investigated in our former studies, [3][4][5] branched micelles or perforated vesicles have never been observed.…”

“…2 In previous studies we could demonstrate that amphiphiles with dendritic oligoglycerol head groups, including chiral derivatives, are promising for the construction of structurally defined supramolecular assemblies with low polydispersity. [3][4][5][6] This type of molecule with extended multifunctional head groups lies at the boundary of classical surfactants and amphiphilic polymers. Their multifunctionality makes them advantageous over classical amphiphiles with linear head groups (e.g.…”

“…comprised of ethoxylate units) as they were proven to produce structurally persistent nanostructures. 3,[7][8][9] The dendritic amphiphiles studied so far [3][4][5][6] combined non-ionic dendritic oligoglycerol head groups of different generations ([G1]-[G3]) with long alkyl chains as lipophilic tail segments, comprising aromatic or non-aromatic linker groups. On the other hand we knew from previous investigations of amphiphilic block copolymers 10 that amphiphiles with fluorinated segments tend to aggregate in aqueous solution into structures of lower curvature as compared to their hydrocarbon analogues.…”

‘Frustrated’ hydrogen bond mediated amphiphile self-assembly – a solid state study

“…1,2 In recent times supramolecular principles have been effectively utilised in the design of novel amphiphiles, giving rise to a new generation of bespoke self-associated nanostructures. [2][3][4][5][6] This has included work by Zhao and co-workers who have shown that low molecular weight, supramolecular-inspired amphiphiles are able to produce self-associated, hydrogen bonded nanocarriers with potential uses as novel drug or gene delivery systems. 7 Work such as this highlights the need to extend our fundamental knowledge of hydrogen bonded network formation within self-associated systems.…”

Stereochemistry‐Controlled Supramolecular Architectures of New Tetrahydroxy‐Functionalised Amphiphilic Carbocyanine Dyes

“…Only homochirality can be detected unambiguously by means of CD spectroscopy. Examples include the non‐chiral cyanine dye C8O3 or the generation of a [1.0] polyglycerol amphiphile reported by Kumar et al . In the latter case, chiral ultra‐structuring of the self‐assembled tubes was detected by CD only in the case of the meso form.…”