Poly(amidoamine) and Poly(propyleneimine) Dendrimers Show Distinct Binding Behaviors with Sodium Dodecyl Sulfate: Insights from SAXS and NMR Analysis

Hierarchical self-assembly of zwitterionic dendrimer-anionic surfactant complexes into multiple stimuli-responsive dynamic nanotubes

Zwitterionic materials attract a wide range of attention due to their unique molecular structures and properties, which make them an interesting candidate to solve multiple problems e.g. in biological and industrial applications. Here, we show that the incorporation of zwitterions into supramolecular assemblies of ionic building blocks can be an effective way to design responsive nanostructures with well-defined morphologies. We report the hierarchical assembly of stimuli-responsive nanotubes with tunable diameters in aqueous solutions via the selective attachment of anionic surfactants to dendrimers with uniquely engineered zwitterionic peripheries. We found that the packing number of the dendrimer-surfactant hybrids can be reversibly controlled, which will trigger their assembly into tubular-like structures. These tubes can grow up to the micro-scale, their diameter is responsive to the ionic strength of the solution, and they can reversibly assemble/disassemble with a change in pH. To the best of our knowledge, this is the first example of dynamic nanotubes formed through controlled ionic interactions involving zwitterionic dendrimers in solution. This not only provides a bottom-up method to make stimuli responsive and dynamic tubes but also introduce a pathway to design complicated nanostructures by controlling the electrostatic interactions of building blocks using zwitterionic functionalities.

Spatial Distributions of Guest Molecule and Hydration Level in Dendrimer-Based Guest-Host Complex

Using the electrostatic complex of G4 poly(amidoamine) (PAMAM) dendrimer with an amphiphilic surfactant as a model system, contrast variation small angle neutron scattering (SANS) is implemented to resolve the key structural characteristics of dendrimer-based guest-host system. Quantifications of the radial distributions of the scattering length density and the hydration level within the complex molecule reveal that the surfactant is embedded in the peripheral region of dendrimer and the steric crowding in this region increases the backfolding of the dendritic segments, thereby reducing the hydration level throughout the complex molecule. The insights into the spatial location of the guest molecules as well as the perturbations of dendrimer conformation and hydration level deduced here are crucial for the delicate design of dendrimer-based guest-host system for biomedical applications.

Conformational transition of a non-associative fluorinated amphiphile in aqueous solution

A non-associative fluorinated amphiphile was synthesized. Instead of self-association at high concentrations, this amphiphile undergoes conformational transition in which the hydrophilic tails wrap around the fluorocarbon core to shield it from water, bearing certain similarity to protein folding in a crowded environment.