Deep eutectic solvents
(DES) are potentially greener solvents obtained
through the complexation of simple precursors which, among other applications,
have been investigated in recent years for their ability to support
the self-assembly of amphiphilic molecules. It is crucial to understand
the factors which influence surfactant solubility and self-assembly
with respect to the interaction of the surfactant molecule with the
DES components. In this work, small-angle neutron scattering (SANS)
has been used to investigate the micellization of cationic (C
n
TAB) and anionic (SDS) surfactants in a ternary
DES comprising choline chloride, urea, and glycerol, where the hydrogen
bond donors are mixed in varying molar ratios. The results show that
in each case either globular or rodlike micelles are formed with the
degree of elongation being directly dependent on the composition of
the DES. It is hypothesized that this composition dependence arises
largely from the poor solubility of the counterions in the DES, especially
at low glycerol content, leading to a tighter binding of the counterion
to the micelle surface and giving rise to micelles with a high aspect
ratio. This potential for accurate control over micelle morphology
presents unique opportunities for rheology control or to develop templated
syntheses of porous materials in DES, utilizing the solvent composition
to tailor micelle shape and size, and hence the pore structure of
the resulting material.
Iron oxide nanoparticle formation in DES was studied in situ across multiple length scales. Initial chloride-containing iron complexes react to form oxygen-rich species which precipitate. Morphology and growth time are defined by solvent composition.
Understanding and manipulating micelle morphology are key to exploiting surfactants in various applications. Recent studies have shown surfactant self-assembly in a variety of Deep Eutectic Solvents (DESs) where both the nature of surfactants and the interaction of the surfactant molecule with the solvent components influence the size, shape, and morphology of the micelles formed. So far, micelle formation has only been reported in type III DESs, consisting solely of organic species. In this work, we have explored the self-assembly of cationic surfactant dodecyl trimethylammonium nitrate/bromide (C12TANO3/C12TAB), anionic surfactant sodium dodecyl sulfate (SDS), and non-ionic surfactants hexaethylene glycol monododecyl ether (C12EO6) and octaethylene glycol monohexadecyl ether (C16EO8) in a type IV DES comprising metal salt, cerium (III) nitrate hexahydrate, and a hydrogen bond donor, urea, in the molar ratio 1:3.5. C12TANO3, C12TAB, C12EO6, and C16EO8 form spherical micelles in the DES with the micelle size dependent on both the surfactant alkyl chain length and the head group, whereas SDS forms cylindrical micelles. We hypothesize that the difference in the micelle shape can be explained by counterion stabilization of the SDS headgroup by polycations in the DES compared to the nitrate/bromide anion interaction in the case of cationic surfactants or molecular interaction of the urea and the salting out effect of (CeNO3)3 in the DES on the alkyl chains/polyethoxy headgroup for non-ionic surfactants. These studies deepen our understanding of amphiphile self-assembly in this novel, ionic, and hydrogen-bonding solvent, raising the opportunity to use these structures as liquid crystalline templates to generate porosity in metal oxides (ceria) that can be synthesized using these DESs.
Deep eutectic systems are currently under intense investigation to replace traditional organic solvents in a range of syntheses. Here, indole in choline chloride-malic acid deep eutectic solvent (DES) was studied as a function of water content, to identify solute interactions with the DES which affect heterocycle reactivity and selectivity, and as a proxy for biomolecule solvation. Empirical Potential Structure Refinement models of neutron diffraction data showed [Cholinium] + cations associate strongly with the indole π-system due to electrostatics, whereas malic acid is only weakly associated. Trace water is sequestered into the DES and does not interact strongly with indole. When water is added to the DES, it does not interact with the indole πsystem but is exclusively in-plane with the heterocyclic rings, forming strong H-bonds with the -NH group, and also weak H-bonds and thus prominent hydrophobic hydration of the indole aromatic region, which could direct selectivity in reactions.
Owing to their large surface area and good solvent processability, polymers of intrinsic microporosity (PIMs) have been widely investigated for gas storage and separation processes. In this article, we show how chemically modifying the polymers can fine-tune their properties for specific, targeted applications. We find that converting the archetypal microporous polymer PIM-1 into a polycarboxylate salt enhances its separation capabilities for H2/CO2 mixtures (relevant to hydrogen production), whereas appending multiple amine groups significantly improves gas separation properties for N2/CO2 mixtures (relevant to flue gas treatment). Adsorption-based separation processes have received less attention than size-sieving processes in porous polymeric materials, however they could provide a suitable alternative technology to energy-intensive separation processes such as cryogenic distillation. We also report the hydrogen storage properties of the modified polymers, which we find to depend on the chemical modification carried out. By coupling the simplicity of the proposed chemical modifications with the scalability and porous properties of PIMs, we provide a blueprint to create new multifunctional materials with adapted properties for targeted applications.
Topical administration of various therapeutic factors at different stages of healing has the potential to enhance wound healing rates and reduce pain of chronic wounds. Here, the potential of utilising therapeutic fibres as wound dressings and/or sutures, is demonstrated by wet-spinning graphene oxide (GO) and aspirin adsorbed GO with polyvinyl alcohol, into drug eluting composite fibres. By varying the load of GO in the composite fibres it was possible to tailor strength, stiffness and stretchability. GO loadings of 5 wt.% resulted in fibres five times stronger than polyvinyl alcohol alone. Low loadings of GO 0.2–0.4 wt.% produced super-stretchable fibres. The drug loaded composite fibres exhibited a slow release of aspirin over a period of 3 d which is attributed to the π–π interactions between the GO and aspirin. These composite fibres demonstrate promise for incorporating other biological factors using GO as a vector, as well as creating textiles that can deliver therapeutics in a sustained manner, leading to flexible wearable therapeutics and sutures in the future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.