Access to Metastable Gel States Using Seeded Self‐Assembly of Low‐Molecular‐Weight Gelators

Abstract

Here we report on howm etastable supramolecular gels can be formed through seeded self-assembly of multicomponent gelators.Hydrazone-based gelators decorated with non-ionic and anionic groups are formed in situ from hydrazide and aldehyde building blocks,a nd lead through multiple self-sorting processes to the formation of heterogeneous gels approaching thermodynamic equilibrium. Interestingly,the addition of seeds composing of oligomers of gelators bypasses the self-sorting processes and accelerates the selfassembly along ak inetically favored pathway,r esulting in homogeneous gels of whichthe network morphologies and gel stiffness are markedly different from the thermodynamically more stable gel products.I mportantly,o ver time,t hese metastable homogeneous gel networks are capable of converting into the thermodynamically more stable state.This seedingdriven formation of out-of-equilibrium supramolecular structures is expected to serve as as imple approach towards functional materials with pathway-dependent properties.

The Power of Confocal Laser Scanning Microscopy in Supramolecular Chemistry: In situ Real‐time Imaging of Stimuli‐Responsive Multicomponent Supramolecular Hydrogels

“…Notably, van Esch et al. successfully visualized the phase‐separated compartmentalized structure in supramolecular hydrogels of tris‐hydrazone gelators that formed from a soluble hydrazide, neutral and anionic aldehydes (Figure a) . By mixing three building blocks in a phosphate buffer, a turbid gel was produced.…”

Biomimetic Strain‐Stiffening Self‐Assembled Hydrogels

“…For this purpose, besides the addition of A , an anionic aldehyde ( A − ) is added to the system to induce the formation of a mixture of gelators consisting of NGs and charged gelators ( CGs : HA 2 A − , HAA − 2 , HA − 3 ) (Figure a) . Charged fibers ( CFs ) are obtained through a seeding‐driven co‐assembly of NGs and CGs (Figure b) . We find that homogeneous hydrogels composed of CFs are formed.…”

“…The total concentration of aldehydes ( A + A − ) was constantly kept at six times higher than H to achieve a complete conversion of H into tris‐hydrazone gelators. To initiate the co‐assembly of NGs and CGs , seeds composed of 1.0 m m NGs were added (see the Supporting Information) . An aldehyde functionalized fluorescein derivative ( A‐FL ) (green, Figure S3) was used to label all the self‐assembled structures; and a cationic dye, Hoechst 33 342 (blue, Figure S3), was used to label the CFs .…”

“…CLSM (green channel) showed that the dimensions of the crosslinked gel fibers were effectively reduced with the content of A − , varying from large clusters with 0 mol % A − to thin bundles with 20 mol % A − (Figure S5), and further to completely homogeneous gel networks with 30 mol % A − of which the microscopic structures cannot be resolved by CLSM (Figure a). Cryo‐TEM studies revealed that such a homogeneous gel network was composed of nano‐sized thin fibers with a diameter of circa 5.8 nm (Figure b), which is comparable to the single hydrazone fibers . In the blue channel of CLSM, we found that the intensity of blue fluorescence increased with the content of A − , indicating the increase in the content of charges of the fibers (Figure S5).…”

“…For the gels prepared with 30 mol % A − , a completely homogeneous blue fluorescence was observed (Figure S5), which therefore demonstrates that the thin fibers are CFs . Indeed, the electrostatic interactions between CFs would effectively prevent the occurrence of bundling, thereby resulting in the homogeneous gel networks …”