Tuning micellar morphology and rheological behaviour of metallo-supramolecular micellar gels

Abstract

Well-defined polystyrene-block-poly(tert-butylacrylate) diblock copolymers end-functionalized by a terpyridine ligand (PS-b-PtBA-[) were synthesized by nitroxide mediated polymerization (NMP) in the presence of an initiator bearing a terpyridine moiety. These materials were then hierarchically organized over two levels of self-assembly to yield metallo-supramolecular micellar gels. The first level of self-assembly is the formation of micelles in the dilute regime. Spherical or cylindrical micelles were obtained depending on the block copolymer composition as well as the method of preparation. The second level of self-assembly was triggered upon addition of Ni(II) ions to the concentrated micellar solutions. Rotational rheometry was used to probe the impact of the micellar morphology and the presence of a co-solvent on the mechanical properties of the gel.

Hydrogen Bonding in Aprotic Solvents, a New Strategy for Gelation of Bioinspired Catecholic Copolymers with N‐Isopropylamide

“…NaOH shows typical elastic gel behavior ( G′ ( ω ) >> G″ (ω), d G′ (ω)/d ω ≈ 0). The loss modulus G″ (ω) exhibits a clear frequency dependency, suggesting fast segmental relaxations typical of supramolecular polymers . At low frequencies, G ″ ( ω ) is low ( δ = 1.2–1.5°), suggesting a quasi ‐permanent network within experimental range, supporting 1 H NMR.…”

“…At high ω, segmental motions, especially dangling ends, increase G″ (ω), being characteristic of supramolecularly bonded networks …”

Structure of Metallo‐Supramolecular Micellar Gels

“…[23][24][25] This copolymer was dissolved in deuterated ethanol, a selective solvent for the PtBA block and a nonsolvent of the PS block. The characteristic features of the resulting micellar solutions in the dilute regime were fi rst investigated by DLS at a concentration of 0.05 g L − 1 .…”

“…[ 21 , 22 ] In this context, we have recently described an original method to trigger the hierarchical self-assembly of block copolymers using metal-ligand interactions. [23][24][25] Firstly, a polystyrene-block -poly( tert -butylacrylate) diblock copolymer bearing a terpyridine moiety at the chain end (PS-b -PtBA-tpy) was dissolved in ethanol, a selective solvent of the PtBA block, to yield micelles composed of a PS core and PtBA coronal chains bearing a terpyridine ligand at their extremity. The second level was then triggered by addition of metal ions resulting in attractive interactions leading to fl ower-like micelles in dilute solutions, [ 23 ] and micellar gels in the concentrated regime.…”

“…Besides the impact of metal ions, our group has recently demonstrated that the morphology of micelles also directs the mechanical properties of the micellar gels. [ 25 ] Interestingly, the possibility to break those metal-ligand complexes holding the micelles together was achieved either by addition of competing ligands or, in a reversible way, by mechanical stresses, leading to materials exhibiting self-healing properties. [ 24 ] Until now, light scattering was used to determine the typical sizes of those micelles in the dilute regime, [ 23 ] while rheology enabled us to probe the mechanical properties of the micellar gels obtained in the concentrated regime.…”