Thomas Sottmann

Nature has skillfully harnessed molecular social behavior, such as “co-assembly” and “self-sorting”, to achieve functional intricacy from simple building blocks. However, the rational control of such “social diversity” in synthetic supramolecular systems remains an unresolved problem. The entropy–enthalpy balance in hydrogelator self-assembly is a crucial thermodynamic parameter to control whether low molecular weight gelators (LMWGs) interact or act autonomously in multicomponent hydrogels. Here we propose that a simple inspection of the hydrogelator solubility vs temperature profile, as measured by 1H NMR, allows us to classify and select single-component hydrogelators in order to combine them at will. Thus, we demonstrate our hypothesis through an investigation of three individual LMWGs, with different solubility profiles, and their pairwise combinations to assess their assembly behavior over molecular, mesoscopic, and macroscopic length scales using a range of techniques. Our data show that one binary mixture exhibits co-assembly to form a unified network hydrogel material, whereas the other combinations display self-sorting, whereby each hydrogelator maintains its own structural integrity and intrinsic material properties. Crucially, temperature is used as an external stimulus to control these systems, providing direct and predictable control over material architecture. Our work highlights how simple NMR solubility measurements manifest the entropy–enthalpy balance as a rational approach to design multicomponent supramolecular materials with multifunctionality from simple and accessible molecular building blocks.

Binders play a key role in fabricating efficient gas diffusion electrodes (GDEs), where catalyst layers are sprayed onto hydrophobic gas diffusion layers (GDLs). In a previous work, we investigated the use of a dry‐pressed single‐layer GDE composed of Polytetrafluoroethylene (PTFE) and SnO ₂ supported on carbon black for CO ₂ reduction to formic acid (FA) with high Faradaic efficiencies (FEs) of 80%–90% at current densities of 200 mA cm ⁻² . However, dry‐pressed single‐layer electrodes suffer from progressive electrowetting and flooding during the reduction. To address these limitations, we transferred this approach to catalyst‐coated hydrophobic GDLs, which require suitable binders/ionomers. We examined Nafion, Sustainion, PTFE, and an imidazolium‐based polymeric ionic liquid (PIL), specifically poly(1‐vinyl‐3‐dodecylimidazolium bromide) (PIL1‐d), which was anticipated to provide enhanced performance. The results demonstrated that incorporation of the PIL significantly improved electrode performance for electrochemical CO ₂ reduction (eCO ₂ RR). This improvement was most pronounced for unsupported SnO ₂ and for larger SnO ₂ nanoparticles (>100 nm). Dynamic light scattering measurements indicated that the PIL already stabilized the SnO ₂ dispersion in the catalyst ink during spray coating through interactions with the oxide nanoparticles. An ionomer loading of 5 wt.% PIL in the catalyst layer was optimal, yielding a maximum FE of 92% FA at 200 mA cm ⁻² .

We report self-assembled organic nanorods based on an acyl hydrazide low-molecular-weight gelator (LMWG) that undergo stimulus-triggered dynamic evolution. Nanorod fabrication starts from a bulk hydrogel in which the LMWG is self-assembled into molecular-scale fibrils (2.8 nm), that assemble into polydisperse flexible nanofibres (diameter ca. 11 nm) with lengths > 500 nm. Sonicating the gel with supernatant water induces reorganisation, creating a homogeneous solution of rigid nanorods with relatively well-defined lengths of ca. 100 nm. Although underpinned by the same molecular-scale fibrils, the nanorods have a monodisperse diameter of 22 nm, double the original nanofibres. Remarkably, these nanorods are stable in water for extended periods of time (> 1 month). On addition of Au(III), in situ reduction to gold nanoparticles (AuNPs) occurs, with the nanorod acyl hydrazide being oxidised to a carboxylic acid. At low Au(III) loadings, the nanorods become decorated with AuNPs and remain dispersed, but at higher Au(III) loadings, the pH falls below the pKa of the resulting carboxylic acid, triggering aggregation to yield an AuNP-loaded gel-like material. Changing pH switches between aggregation/dispersion via protonation/deprotonation. The nanorods can be functionalised by reacting the acyl hydrazide, for example with the ketone in doxorubicin (Dox). The bulk gel is modified, and sonication gives Dox-loaded nanorods. In summary, we report stable nanorods based on a simple LMWG that evolve in response to stimuli and can be derivatised with bioactive agents – we anticipate future biomedical applications.

Sustainable biosurfactants, such as rhamnolipids (RL), have been attracting increasing attention because of their enhanced biocompatibility and high biodegradability compared to conventional synthetic surfactants. To enable large-scale application of rhamnolipids, such as cleaning or washing, we studied symmetric, biocompatible microemulsions of the type H2O (KCl brine)–isopropyl myristate (IPM)–di-RL (Rha2C10C10)–alkane-1,2-diol. We present a systematic study on the influence of major formulation parameters, namely temperature, salinity, pH, and co-surfactant chain length, on the phase behavior and nanostructure. At pH = 8.0 ≫ pKa, Rha2C10C10 behaves similarly to double-tail anionic surfactants, including AOT, and does not form oil-continuous microemulsions at low salinities. At higher salinities, a classical fish phase diagram with a three-phase body was observed, implying that the addition of octane-1,2-diol causes an inversion of the amphiphilic film curvature from being curved around IPM to around brine. Lowering the pH to pH = 6.0 ∼ pKa leads to the partial protonation of the di-RL and a more hydrophobic behavior. Longer chain alkanediols substantially improve the solubilization efficiency of the amphiphile mixture. Small-angle neutron scattering (SANS) measurements showed an interaction peak at low q with values of the amphiphilicity factor fa around −0.7, confirming the presence of well-structured microemulsions. Data analysis at high q with a modified Porod law revealed surprisingly low values of blurriness t, in view of the di-RL’s large headgroup, and a geometrical factor a significantly larger than predicted by models of the bicontinuous structure. Both observations might be linked to a scattering contribution of the bulky sugar head groups. Finally, at high pH and low salinity, an additional high-q scattering feature is observed, which could be related to the packing of the rhamnose moieties or to the local segregation of di-RLs and alkane-1,2-diols in the amphiphilic film.

The immobilization of molecular catalysts in confined geometries of mesoporous support materials has been shown to selectively control catalytic performances. An additional in-crease in yield and selectivity of the catalytic reaction is expected by the combination of the spatial confinement of the pores with an ionic liquid thin film at the pore surface. Small angle X-ray scattering (SAXS) can provide an important contribution to the structural characterization of such materials. Here we investigate the structure of unfilled and EMIM-PF6-filled porous SFB-15 produced via true liquid crystal templating using SAXS. In particular, the focus of this work was set on mesoporous silica materials with cylindrical mesopores ordered in a two-dimensional hexagonal lattice and pore radii of rpore = 3.7 nm. Taking into account the scattering contributions from the silica grain surfaces, as well as meso- and micropores, the combination of appropriate form and structure factor models allowed to determine essential structural parameters, such as the lattice parameter, the pore radius as well as the thickness and correlation length of a microporous corona. Finally, the growth of the EMIM-PF6 liquid film induced by the loading of the porous materials with EMIM-PF6 could be monitored by systematic SAXS measurements. By knowing the relationship between filling degree, i.e. EMIM-PF6 pore volume fraction φ_IL and film thickness, it is now possible to set the optimal EMIM-PF6 film thickness required for SILP catalysis.

Sustainability has become essential in addressing the substitution of depleting fossil‐based resources with bio‐renewable alternatives, including products active at interfaces, such as surfactants. Enhancing their efficiency reduces both ecological and economic impact. Here, we present amphiphilic poly(ethylene glycol)‐ b ‐poly(terpenyl glycidyl ether) diblock copolymers synthesized via anionic ring‐opening polymerization from two terpenyl glycidyl ethers (TGE) based on the naturally occurring terpenoid farnesol, farnesyl glycidyl ether (FarGE), and its hydrogenated derivative hexahydrofarnesyl glycidyl ether (HHFarGE). Using poly(ethylene glycol) monomethyl ether (mPEG ₁₁₄ ) as a macroinitiator resulted in controlled molecular weights (5600 – 8400 g·mol ⁻¹ ) with low dispersities Đ (1.04–1.07). Fluorescence spectroscopy and light scattering revealed low critical micelle concentrations with a systematic decrease with increasing TGE block size due to the hydrophobic effect. The addition of small amounts of mPEG ₁₁₄ ‐ b ‐PTGE _m to microemulsions leads to a significant increase of the solubilization efficiency not limited to conventional H ₂ O/NaCl – n ‐decane – tetraethylene glycol monodecyl ether microemulsions, but also in sustainable H ₂ O – isopropyl myristate – n ‐octyl β‐D‐glucopyranoside – farnesol formulations, serving as model systems for cosmetic applications. Using SANS, we observed that adsorption of the copolymer at the amphiphilic film leads to an increased structural order of bicontinuous microemulsions due to a higher film bending rigidity.

High-pressure SANS shows that the influence of pressure on the nanostructure of application-relevant bicontinuous microemulsions is amplified in the presence of propane, where a notably lower structural order than in n -decane microemulsions is found.

Poly((−)-dihydrocarvide) is synthesized via yttrium-mediated ring-opening polymerization. Block copolymerization and functionalization yield semi-crystalline and brush polymers, highlighting its versatility in copolymer design.

We address the structure of homogeneous mixtures of equal volumes of water and oil rendered miscible by the addition of amphiphilic molecules. Specifically, we study the pathway from regular ternary solutions to structured microemulsions with increasing amphiphilic chain length, i.e., increasing i and j for alkyl polyglycol ether surfactants (C_iE_j) from C₃E₀ (i.e., propanol) to C₅E₂, using contrast variation small angle neutron scattering (SANS). The bulk-contrast SANS pattern of the symmetric system water – cyclohexane – (2-propanol/1-propanol) with nearly horizontal tie-lines matches Ornstein-Zernike behavior with characteristic q^-2 decay, implying critical composition fluctuations occurring predominantly in the water-oil ratio. Weak scattering signals were detected in film-contrast SANS possibly due to the existence of the nearby tricritical point (TCP). After passing the TCP, the increasing the amphiphilic strength leads to the gradual build-up of well-defined amphiphilic interfaces stabilizing water- and oil-rich domains of colloidal dimensions, as evidenced by the well-known q^-4 behavior observed in bulk-contrast SANS pattern at large q. The amphiphilicity factor fa ranging from +1.15 to -0.60 reveals the crossing of the disorder line, the Lifshitz line, and the wetting to non-wetting transition. Precursors of structuring in those mixtures with compositions, where the lamellar phase appears for even longer-chain amphiphiles, are also borne out by the experiments.