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Abstract: Ionic liquids (ILs) offer tunable physicochemical properties but are often limited by their high viscosities. This is commonly addressed by introducing low-viscosity diluents, which increase molecular complexity and frequently lead to nonlinear viscosity–composition relationships. Here, we designed a molecular diluent that mimics the parent IL. We demonstrate that this approach enables viscosity tuning over 3 orders of magnitude while preserving the self-assembled nanostructure of the neat IL across all compositions. This work establishes a new strategy for designing IL–diluent systems and provides a model platform to investigate the role of Coulombic interactions in governing the local structure and macroscopic properties.

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Abstract: Supramolecular soft materials derived from low molecular weight gelators (LMWG) have been widely prepared using pH-switching strategies, in which the method of inducing the pH change plays a critical role in determining material properties and applications. In this thesis, three distinct pH-switching approaches were explored. Although each approach relies on a change in pH, it has been demonstrated that they produce materials with significantly different behaviours, structures, and functionalities. In chapter 2, plasma-induced gelation was investigated as a novel route for the in situ fabrication and 3D printing of supramolecular hydrogels. It was demonstrated that cold atmospheric plasma enables precise spatial and temporal control over gelation, allowing the formation of complex, patterned, and multilayered structures with defined geometries. Studies using Kineticolor showed that gelation is driven by plasma-induced pH changes. It was further demonstrated that this approach can be combined with the in situ formation of gold nanoparticles, enabling the fabrication of composite hydrogels with enhanced functionality. In Chapter 3, transient pH-switching systems were explored by combining a urea/urease reaction with formate hydrolysis in DMSO/H₂O hydrogel systems. The scope of the system was expanded by incorporating a range of LMWGs, and it was demonstrated that variation of the ester component, including methyl, ethyl, and n-propyl formate, allows control over hydrolysis rates and thus temporal behaviour. The effects of temperature and ageing were also investigated, revealing complex, non-linear, and sometimes unpredictable dynamics that are important for practical applications. In chapter 4, these pH triggers were further applied to a lipid-based system, where it was demonstrated that they can induce and control phase transitions in a monoolein-oleic acid mixture. Using flow-through small-angle X-ray scattering transitions, including Pn3m-to-HII, HII-to-Im3m, and HII-to-Im3m-to-HII, were successfully realised. It was shown that these nanoscale structural changes significantly influence the macroscopic properties of the materials, highlighting the versatility of transient pH control across different supramolecular systems. Finally, in chapter 5, electrochemically induced gelation and polymerisation of carbazole-functionalised amino acid-based hydrogels were investigated. In situ electrochemical small-angle X-ray scattering was used to examine the dynamic processes of self-assembly and polymerisation, showing how subtle molecular changes govern structural evolution and material properties. Overall, this thesis demonstrates that the choice of gelation method enables tailoring of material structure, dynamics, and functionality across multiple length scales.

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Abstract: The Grotthuss mechanism is a proton conduction mechanism where proton transports through the hydrogen-bonding network of water molecules. This mechanism enables high ionic conductivity, which is well utilized in nature and some proton-active artificial devices. Since this mechanism requires cleavage and reformation of hydrogen-bonding networks, its activation energy (Ea) is generally in the range of 10–15 kJ mol–1. Aiming to create a new mechanism beyond the Grotthuss mechanism, we focused on the surface proton hopping conduction (SPHC) mechanism, where a proton hops between neighboring sulfonate groups via bound water molecules. Generally, the SPHC mechanism requires a large Ea. Our idea is that constructing densely aligned sulfonate groups should lead to small Ea (≤10 kJ mol–1) and high proton transport efficiency. To realize high-density alignment of sulfonate groups with an average distance of ca. 5 Å, we employed the self-assembly of a liquid-crystalline (LC) discotic molecule TPES. TPES self-assembled into a hexagonal columnar LC structure in the presence of an appropriate amount of water. The TPES/H2O mixtures showed a maximum proton conductivity of 3.5 × 10–1 S cm–1 at 30 °C and a small Ea of 6.0 kJ mol–1 when the water content X = 53 wt %. We confirmed that extremely fast proton conduction and a small Ea were achieved through only bound water. The dynamics of this bound water were quantitatively evaluated by QENS measurement. These results led us to conclude that the high proton conductivity in the columnar LC materials is primarily based on an extremely activated SPHC mechanism.

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Abstract: The formation of chiral structures from achiral building blocks, and the propagation of chirality across length-scales in soft matter are still poorly understood phenomena. Here, we have studied a system revealing an exceptional diversity of spontaneously chiral phases formed by achiral mesogenic dimers linked by spacers with an odd number of atoms. Depending on terminal chain length and temperature, these compounds form a well-known heliconical nematic (NTB) phase and distinct helical smectic phases - ranging from the nanoscale-pitch SmCTB–SH, through the SmCTB–DH phase with ~ 50 nm periodicity, to the newly identified SmCTB–C phase featuring a micron-scale helix. In the SmCTB–C phase heliconical order is preserved even though the interlayer molecular intercalations strongly suppress the azimuthal rotation of the director. Resonant soft X-ray scattering (RSoXS) measurements were performed for the first time across an entire homologous series. Results confirmed the double-helical structure of the SmCTB–DH phase in which a longer helix is superimposed on the short one. The intensity of the resonant signals revealed an anomaly: the non-monotonic temperature evolution is due to the transient passage of the structure from a four-layer helix, through a nearly perfect three-layer clock-like helix, before decoupling of the short and long helices at lower temperatures.

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Abstract: We report a simple design strategy to introduce lithium-responsiveness into N-capped peptide low-molecular-weight gelators by incorporating the FFD tripeptide motif (FF extended with Asp). Asp adds an oxygen-rich carboxylate residue that enables cation-mediated assembly. In high pH aqueous solutions, 2NapFFD shows a pronounced cation selectivity. Li+ generates highly viscous, shear-thinning solutions with birefringent textures, while other Group 1 metals and bulky organic counterions result in low-viscosity and weakly ordered solutions. SAXS and SANS reveal that the addition of Li+ produces substantially extended micellar structures consistent with long cylindrical assemblies, whereas other monovalent cations lead to the formation of short cylindrical objects. The Li+ selectivity is intrinsic to the FFD sequence, with other aromatic caps tuning packing and mesoscale order. Finally, dialysis-driven Li+ exchange induces gelation and enables us to quantify the Li+ uptake by ICP-OES, illustrating potential for selective lithium capture.