Thermo-responsive properties of metallo-supramolecular block copolymer micellar hydrogels

Amphiphilic poly(ether urethanes) carrying associative terpyridine side groups with controlled spacing

A synthesis for metallo-supramolecular crosslinkable polyurethanes with uniform vs. random sticker spacings is presented to study how sticker density and distribution affect the mechanical properties of the corresponding gels.

A metalloprotein-inspired thermo-gene for thermogels

Coordinating hydrogels may act as a thermo-gene to endow heat-melting conventional hydrogels with superior thermal stability at temperatures over 80 °C.

Thermo- and redox-responsive dendronized polymer hydrogels

Unique supramolecular coordination of Fe²⁺ with terpyridine afford these hydrogels redox-responsive sol–gel transitions, while characteristic thermoresponsive properties from OEG-based first generation dendronized polymers render these hydrogels thermally-induced macroscopical volume changes and enhanced mechanical properties.

The effect of metal ions on the viscoelastic properties of thermosensitive sol-to-gel reversible metallo-supramolecular hydrogels

Fine-tuning of thermo-induced assembly and rheological behaviour of hydrogels based on a copolymer having two distinct hydrophilic blocks via metal ions.

Synthesis and characterization of metallo-supramolecular polymers from thiophene-based unimers bearing pybox ligands

A series of novel metallo-supramolecular polymers was prepared, based on 2,6-bis(2-oxazolinyl)pyridine chelating groups bridged with thiophene, bithiophene and thienothiophene as a linker, beginning from commercially available (chelidamic) acid.

Orthogonal Control of the Dynamics of Supramolecular Gels from Heterotelechelic Associating Polymers

One of the first examples of supramolecular gels presenting independent dual dynamics is built through a combination of hydrophobic and metal-ligand interactions. The associating building block consists in a water-soluble linear polymer terminated by a short hydrophobic sticker at one end, and a coordinating moiety at the other end. The distinct supramolecular nature of these noninterfering binding motifs allows the dynamics of the hydrogels to be finely tuned in an orthogonal fashion by the application of specific stimuli. Precisely, the solvent-induced plasticization of the hydrophobic associations and the acid-promoted dissociation of the metal-ligand complexes are used to control the network dynamics. By opposition to classically encountered binary gel-sol responses, we demonstrate that the stimuli-induced transition in material properties can be gradual, provided that the material structure is well designed and strong enough.

Supramolecular polymer networks: hydrogels and bulk materials

Supramolecular polymer networks are materials crosslinked by reversible supramolecular interactions, such as hydrogen bonding or electrostatic interactions. Supramolecular materials show very interesting and useful properties resulting from their dynamic nature, such as self-healing, stimuli-responsiveness and adaptability. Here we will discuss recent progress in polymer-based supramolecular networks for the formation of hydrogels and bulk materials.

Sol–gel reversible metallo-supramolecular hydrogels based on a thermoresponsive double hydrophilic block copolymer

A new thermoresponsive double hydrophilic block copolymer bearing a terpyridine moiety formed a hydrogel with a sol–gel thermoreversible transition in the presence of Fe²⁺ ions.

Precise Control over the Rheological Behavior of Associating Stimuli-Responsive Block Copolymer Gels

"Smart" materials have considerably evolved over the last few years for specific applications. They rely on intelligent macromolecules or (supra-)molecular motifs to adapt their structure and properties in response to external triggers. Here, a supramolecular stimuli-responsive polymer gel is constructed from heterotelechelic double hydrophilic block copolymers that incorporate thermo-responsive sequences. These macromolecular building units are synthesized via a three-step controlled radical copolymerization and then hierarchically assembled to yield coordination micellar hydrogels. The dynamic mechanical properties of this particular class of materials are studied in shear flow and finely tuned via temperature changes. Notably, rheological experiments show that structurally reinforcing the micellar network nodes leads to precise tuning of the viscoelastic response and yield behavior of the material. Hence, they constitute promising candidates for specific applications, such as mechano-sensors.

Directional supracolloidal self-assembly via dynamic covalent bonds and metal coordination

An emerging strategy towards the sophistication of supramolecular nanomaterials is the use of supracolloidal self-assembly, in which micelles or colloids are used as building blocks. Binding directionality can produce nanostructures with attractive properties. Herein, we present a new directional supracolloidal self-assembly by virtue of dynamic covalent bonds and metal coordination in water. Conjugation of a ligand precursor to a water-soluble block copolymer through dynamic covalent bonds leads to the dehydration and micellization of the functionalized polymer. Reversible reaction facilitates the permeation of metal ions into core-shell interfaces. Conversely, metal-coordination promotes reaction over the interfaces. Cu(ii)-coordination occurs overwhelmingly inside each isolated micelle. However, Zn(ii)-coordination induced a directional self-assembly whose nanostructures evolve stepwise from nanorods, nanowires, necklaces, and finally to supracolloidal networks scaling-up to several tens of micrometres. Post-reactions of simultaneous dynamic covalent bond conversion and Zn(ii)-coordination over the core-shell interfaces endow these supracolloidal networks with a huge specific surface area for hydrophobic dative metal centres accessible to substrates in water. Water-soluble shells play important roles in directional supracolloidal assembly and in the stabilization of nanostructures. Thus the directional self-assembly provides a versatile platform to produce metallo-hybridized nanomaterials that are promising as enzyme-inspired aqueous catalysts.

Revealing the supramolecular nature of side-chain terpyridine-functionalized polymer networks

Nowadays, finely controlling the mechanical properties of polymeric materials is possible by incorporating supramolecular motifs into their architecture. In this context, the synthesis of a side-chain terpyridine-functionalized poly(2-(dimethylamino)ethyl methacrylate) is reported via reversible addition-fragmentation chain transfer polymerization. By addition of transition metal ions, concentrated aqueous solutions of this polymer turn into metallo-supramolecular hydrogels whose dynamic mechanical properties are investigated by rotational rheometry. Hence, the possibility for the material to relax mechanical constrains via dissociation of transient cross-links is brought into light. In addition, the complex phenomena occurring under large oscillatory shear are interpreted in the context of transient networks.

Self-assembly and disassembly of a redox-responsive ferrocene-containing amphiphilic block copolymer for controlled release

The synthesis and self-assembly of ferrocene-containing block copolymers PEG-b-PMAEFc, and the encapsulation and redox-responsive release of a model molecule (rhodamine B) upon external redox stimuli (H₂O₂).