Low-molecular-weight gels show great potential for application in fields ranging from the petrochemical industry to healthcare and tissue engineering. These supramolecular gels are often metastable materials, which implies that their properties are, at least partially, kinetically controlled. Here we show how the mechanical properties and structure of these materials can be controlled directly by catalytic action. We show how in situ catalysis of the formation of gelator molecules can be used to accelerate the formation of supramolecular hydrogels, which drastically enhances their resulting mechanical properties. Using acid or nucleophilic aniline catalysis, it is possible to make supramolecular hydrogels with tunable gel-strength in a matter of minutes, under ambient conditions, starting from simple soluble building blocks. By changing the rate of formation of the gelator molecules using a catalyst, the overall rate of gelation and the resulting gel morphology are affected, which provides access to metastable gel states with improved mechanical strength and appearance despite an identical gelator composition.

Spatial control over the self-assembly of synthetic molecular fibers through the use of light-switchable catalysts can lead to the controlled formation of micropatterns made up of hydrogel structures. A photochromic switch, capable of reversibly releasing a proton upon irradiation, can act as a catalyst for in situ chemical bond formation between otherwise soluble building blocks, thereby leading to fiber formation and gelation in water. The use of a photoswitchable catalyst allows control over the distribution as well as the mechanical properties of the hydrogel material. By using homemade photomasks, spatially structured hydrogels were formed starting from bulk solutions of small molecule gelator precursors through light-triggered local catalyst activation.

Dissipative self-assembly is a process in which energy-consuming chemical reaction networks drive the assembly of molecules. Prominent examples from biology include the GTP-fueled microtubule and ATP-driven actin assembly. Pattern formation and oscillatory behavior are some of the unique properties of the emerging assemblies. While artificial counterparts exist, researchers have not observed such complex responses. One reason for the missing complexity is the lack of feedback mechanisms of the assemblies on their chemical reaction network. In this work, we describe the dissipative self-assembly of colloids that protect the hydrolysis of their building blocks. The mechanism of inhibition is generalized and explored for other building blocks. We show that we can tune the level of inhibition by the assemblies. Finally, we show that the robustness of the assemblies towards starvation is affected by the degree of inhibition.

Hierarchical compartmentalization through the bottom-up approach is ubiquitous in living cells but remains a formidable task in synthetic systems. Here we report on hierarchically compartmentalized supramolecular gels that are spontaneously formed by multilevel self-sorting. Two types of molecular gelators are formed in situ from nonassembling building blocks and self-assemble into distinct gel fibers through a kinetic self-sorting process; interestingly, these distinct fibers further self-sort into separated microdomains, leading to microscale compartmentalized gel networks. Such spontaneously multilevel self-sorting systems provide a “bottom-up” approach toward hierarchically structured functional materials and may play a role in intracellular organization.

Self-assembly provides access to a variety of molecular materials, yet spatial control over structure formation remains difficult to achieve. Here we show how reaction–diffusion (RD) can be coupled to a molecular self-assembly process to generate macroscopic free-standing objects with control over shape, size, and functionality. In RD, two or more reactants diffuse from different positions to give rise to spatially defined structures on reaction. We demonstrate that RD can be used to locally control formation and self-assembly of hydrazone molecular gelators from their non-assembling precursors, leading to soft, free-standing hydrogel objects with sizes ranging from several hundred micrometres up to centimeters. Different chemical functionalities and gradients can easily be integrated in the hydrogel objects by using different reactants. Our methodology, together with the vast range of organic reactions and self-assembling building blocks, provides a general approach towards the programmed fabrication of soft microscale objects with controlled functionality and shape.

Single-walled carbon nanotubes (SWCNTs) are functionalized with a spiropyran derivative, which is attached non-covalently to the SWCNT's sidewall via a pyrene anchor group. Using this non-covalent functionalization strategy, individual SWCNTs can be stabilized in solution without the need for additional surfactants. Bright luminescence confirms the presence of individual tubes in the thus-prepared samples. In these samples, the majority of pyrene-spiropyran molecules are attached to the walls of the SWCNTs. Upon complex formation with the SWCNT, the switching moiety retains its ability to switch, i.e., to undergo reversible transformations between the closed spiropyran and the opened merocyanine form, and is stable over many cycles of operation

A facile, cost-effective synthesis of a Ti3C2T x (MXene) based polyindole nanocomposite has been explored in detail as both, a cathode and anode, for the fabrication of symmetric and asymmetric supercapacitor devices. The morphological analysis confirmed successful intercalation as well as coating of polyindole on MXene nanosheets. The concentration of polyindole was optimized with respect to MXene for optimum electrochemical performance. Surface area analysis confirmed the highest specific surface area for the MXene-Polyindole composite system with a 3:1 ratio of MXene and polyindole. The high specific capacitance of 226.5 F g–1, at 2 A g–1, current density and excellent cyclic stability of 90.5% after 8000 cycles were achieved for this nanocomposite. The designed asymmetric device with this composite as an anode achieved maximum specific capacitance of 117 F g–1 and energy density of 65.3 Wh kg–1. Most importantly, the MXene based composite displayed excellent electrochemical performance as both an anode and cathode in an asymmetric supercapacitor device. Moreover, the device was used to light up LEDs of different colors and power up a mini fan. With these electrochemical properties, this MXene-based hybrid composite can be considered as a potential candidate for next-generation supercapacitor devices.

In situ multicomponent hydrogelator formation enables straightforward chemical functionalisation of supramolecular hydrogels.