Two Robust Strategies toward Hydrogels from Quenched Block Copolymer Nanofibrillar Micelles

Abstract

While the formation of (tri)block copolymer hydrogels has been extensively investigated, such studies mostly focused on equilibrium self-assembling whereas the use of preformed structures as building blocks such as out of equilibrium, quenched, nanofibrillar micelles is still a challenge. Here, we demonstrate that quenched, ultralong polystyrene-b-poly(ethylene oxide) (PS-b-PEO) micelles can be used as robust precursors of hydrogels. Two cross-linking strategies, (i) thermal fusion of micellar cores and (ii) chemical cross-linking of preformed micellar coronas were studied. The gelation process and the structure of the micellar networks were investigated by in situ rheological measurements, confocal microscopy and transmission electron microscopy. Direct observation of core fusion of preformed quenched micelles is provided validating this method as a robust gelation route. Using time sweep rheological experiments, it was found for both cross-linking methods that these 3D “mikado” gels are formed in three different stages, containing (1) initiation, (2) transition (growth), and (3) stabilization regimes.

Structural Evolution of a Polystyrene-Block-Poly(Ethylene Oxide) Block Copolymer in Tetrahydrofuran/Water Cosolvents

“…Our system is different from the previous studies − because the sticky gel that contains PS 317 -b-PEO 307 in the THF/water (1/0.22) cosolvent does not display the prominent features corresponding to the scattering of core–shell micelles. Instead, a Bragg peak is displayed, together with power-law intensity decays.…”

“…The aggregation of the patchy micelles usually forms fractal networks, which further freezes the liquid. − In fact, patchy micelles of various morphologies are frequently reported . Similar to fractal networks of patchy micelles, fibrillar networks (also called worm-like micelles or branched cylinders) are frequently obtained for gels or viscous solutions. − …”

“…The gelation observed in this study is different from the gelation of patchy micelles and cylindrical micelles. Previous studies have demonstrated that the gelation of BCP solutions relies on micellar morphologies (i.e., patchy micelles − and cylindrical micelles − ). Obtaining patchy micelles or cylindrical micelles needs fine controls over several morphological factors, such as molecular weight and volume fraction, of BCPs. − ,− Nevertheless, the gel observed in this study was independent of volume fractions of constituent PS and PEO blocks.…”

Spatial Manipulation and Integration of Supramolecular Filaments on Hydrogel Substrates towards Advanced Soft Devices

“…It should be noted that with the aim of immobilizing the micelles on DexMA hydrogel, the PS-b-PEO micelles used here were partially functionalized with methacrylate (denoted as PS-b-PEO(MA)) through ac o-assembly approach. [17] Briefly,amixture of methacrylated PS-b-PEO block copolymers (PS-b-PEO-MA) and pristine PS-b-PEO block copolymers was used in the evaporation-induced self-assembly process.T hrough copolymerization with DexMA in the laser illuminated region (Figure 1c-2), PS-b-PEO(MA) micelles were capable of bonding onto DexMA hydrogel. This was confirmed by the formation of ahybrid structure that micellar filaments were embedded on the surface of hydrogels (Figure 1c-3).…”

Polymeric Nanowires for Diagnostic Applications

“…Furthermore, it has been shown that quenched micelles, containing a glassy core, exhibit such a length without branching. Zhang et al [27] presented such micelles, with lengths of up to 250 μm. The amphiphilic nature of the building blocks opens up many options when it comes to integration of different molecules into the core while keeping the solubility in a solvent unimpeded.…”