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[Display omitted] Nonionic surfactant aerosols play a crucial role in many industries, but they can cause acute irritation to users' eyes during spraying. This cytotoxic process is associated with corneal cell necrosis causing cell membrane disruption. Industrial grade surfactants are typically polydisperse mixtures described by their nominal chemical structure but how the polydispersity affects their interactions with cell membrane, remains largely unexplored. A better understanding could benefit product formulations to maximise their efficiency whilst minimising their toxicity to the users. In this study, poly - oxyethylene glycol monododecyl ethers (C 12 E 4 , C 12 E 23) were used to form ideal binary surfactant mixtures. The cytotoxicities of mono and polydispersed surfactants towards human corneal epithelial cells were examined, followed by a series of biophysical characterisations of interactions between surfactants and model cell membranes. Notably, to probe the journey of individual C 12 E 4 and C 12 E 23 surfactant molecules across the cell membrane from a binary surfactant mixture, "two-colour" neutron reflection measurements were achieved via Hydrogen/Deuterium substitution. The relative distributions of C 12 E 4 and C 12 E 23 across cell membranes and their nanostructural conformations revealed a synergistic membrane-lytic ability initiated by surfactant mixing, with the more hydrophobic C 12 E 4 exhibiting stronger membrane binding potency than the hydrophilic C 12 E 23. The exact molar ratio of C 12 E 4 against C 12 E 23 in the mixture determined how the mixed surfactant interacted with the cell membrane, and how the process directly impacted cytotoxicity and eye irritation. Thus, the cytotoxicity of polydisperse surfactants is not the same as monodisperse surfactant of the same average structure. This work provides a useful basis for the assessment of surfactant mixing by balancing their efficiency and toxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] Colloidal suspensions of anisotropic particles are ubiquitous in particle-based industries. Consequently, there is a need to quantify the effects of particle shape on equilibrium phases and kinetic state transitions, particularly at lower aspect ratios (L / D ≈ 1–10). We present a new, colloidal system comprised of hollow, octadecyl-coated silica rods with 40 nm diameter with controlled aspect ratio and thermoreversible short-range attractions. Rheology and dynamic light scattering measurements on suspensions of these hollow adhesive hard rods with nominal aspect ratio ≈3 suspended in tetradecane exhibit thermoreversible gelation without complicating effects of gravitational settling. Small angle neutron scattering measurements of the microstructure are analyzed to determine the effective strength of attraction in the form of Baxter sticky parameter. Quantitative agreement is found with simulation predictions of the thermoreversible gel transition as a function of volume fraction, further validating a universal state diagram and providing guidance for the effects of aspect ratio on gelation. [ABSTRACT FROM AUTHOR]

The formation of distorted lamellar phases, distinguished by their arrangement of crumpled, stacked layers, is frequently accompanied by the disruption of long-range order, leading to the formation of interconnected network structures commonly observed in the sponge phase. Nevertheless, traditional scattering functions grounded in deterministic modeling fall short of fully representing these intricate structural characteristics. Our hypothesis posits that a deep learning method, in conjunction with the generalized leveled wave approach used for describing structural features of distorted lamellar phases, can quantitatively unveil the inherent spatial correlations within these phases. This report outlines a novel strategy that integrates convolutional neural networks and variational autoencoders, supported by stochastically generated density fluctuations, into a regression analysis framework for extracting structural features of distorted lamellar phases from small angle neutron scattering data. To evaluate the efficacy of our proposed approach, we conducted computational accuracy assessments and applied it to the analysis of experimentally measured small angle neutron scattering spectra of AOT surfactant solutions, a frequently studied lamellar system. The findings unambiguously demonstrate that deep learning provides a dependable and quantitative approach for investigating the morphology of wide variations of distorted lamellar phases. It is adaptable for deciphering structures from the lamellar to sponge phase including intermediate structures exhibiting fused topological features. This research highlights the effectiveness of deep learning methods in tackling complex issues in the field of soft matter structural analysis and beyond. [ABSTRACT FROM AUTHOR]

[Display omitted] Aqueous suspensions of cellulose nanocrystals (CNC) form a re-entrant liquid crystal (LC) phase with increasing salinity. Phase separation occurs in this LC state leading to a biphasic gel with a flow programmable structure that can be used to form anisotropic soft materials. We term this state a Liquid Crystal Hydroglass (LCH). Defining the mechanisms by which the LCH forms requires detailed structural analysis at the mesoscopic length scale. By utilising Small Angle Neutron Scattering (SANS), we investigated the microstructure transitions in CNC suspensions, with a particular focus on the unique LC re-entrancy and gelation into the biphasic LCH. Scattering from LCH gels comprises contributions from a dispersed liquid state and static heterogeneity, characterised using a Lorentzian-Gaussian model of inhomogeneity. This conceptually supports a gelation mechanism (spinodal decomposition) in CNC suspensions towards a biphasic structure of the LCH. It also demonstrates that, with increasing salinity, the non-monotonic variation in effective volume fraction of CNC rods fundamentally causes the LC re-entrancy. This work provides the first experimental characterisation of the LC-re-entrancy and formation of an anisotropic LCH gel. The proposed mechanism can be extended to understanding the general behaviour of anisotropic colloids. [ABSTRACT FROM AUTHOR]

[Display omitted] The self-assembly structures and phase behaviour of phospholipids in protic ionic liquids (ILs) depend on intermolecular forces that can be controlled through changes in the size, polarity, and H-bond capacity of the solvent. The structure and temperature stability of the self-assembled phases formed by four phospholipids in three ILs was determined by a combination of small- and wide-angle X-ray scattering (SAXS and WAXS) and small-angle neutron scattering (SANS). The phospholipids have identical phosphocholine head groups but different alkyl tail lengths and saturations (DOPC, POPC, DPPC and DSPC), while the ILs' amphiphilicity, H–bond network density and polarity are varied between propylammonium nitrate (PAN) to ethylammonium nitrate (EAN) to ethanolammonium nitrate (EtAN). The observed structures and phase behaviour of the lipids becomes more surfactant–like with decreasing average solvent polarity, H-bond network density and surface tension. In PAN, all the investigated phospholipids behave like surfactants in water. In EAN they exhibit anomalous phase sequences and unexpected transitions as a function of temperature, while EtAN supports structures that share characteristics with water and EAN. Structures formed are also sensitive to proximity to the lipid chain melting temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] Enveloped viruses are pivotal in causing various illnesses, including influenza and COVID-19. The antimicrobial peptide LL-37, a critical part of the human innate immune system, exhibits potential as an antiviral agent capable of thwarting these viral threats. Its mode of action involves versatile and non-specific interactions that culminate in dismantling the viral envelope, ultimately rendering the viruses inert. However, the exact mechanism of action is not yet understood. Here, the mechanism of LL-37 triggered changes in the structure and function of an enveloped virus is investigated. The bacteriophage "Phi6" is used as a surrogate for pathogenic enveloped viruses. Small angle X-ray and neutron scattering combined with light scattering techniques demonstrate that LL-37 actively integrates into the virus's lipid envelope. LL-37 addition to Phi6 leads to curvature modification in the lipid bilayer, ultimately separating the envelope from the nucleocapsid. Additional biological assays confirm the loss of virus infectivity in the presence of LL-37, which coincides with the structural transformations. The results provide a fundamental understanding of the structure-activity relationship related to enveloped viruses. The knowledge of peptide-virus interactions can guide the design of future peptide-based antiviral drugs and therapies. [ABSTRACT FROM AUTHOR]

[Display omitted] The forces that govern lipid self-assembly ionic liquids are similar to water, but their different balance can result in unexpected behaviour. The self-assembly behaviour and phase equilibria of two phospholipids, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), in the most common protic ionic liquid, ethylammonium nitrate (EAN) have been investigated as function of composition and temperature by small- and wide-angle X-ray scattering (SAXS/WAXS) and small-angle neutron scattering (SANS). Both lipids form unusual self-assembly structures and show complex and unexpected phase behaviour unlike that seen in water; DSPC undergoes a gel L β to crystalline L c phase transition on warming, while POPC forms worm-like micelles L 1 upon dilution. This surprising phase behaviour is attributed to the large size of the EAN ions that solvate the lipid headgroup compared to water changing amphiphile packing. Weaker H-bonding between EAN and lipid headgroups also contributes. These results provide new insight for the design of lipid based nanostructured materials in ionic liquids with atypical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] The superchaotropic Keggin polyoxometalate α-SiW 12 O 40 4− (SiW) was recently shown to stabilize non-ionic surfactant (C 18:1 E 10) foams owing to electrostatic repulsion that arises from the adsorption of SiW-ions to the foam interfaces. The precise mechanism of foam stabilization by SiW however remained unsolved. Imaging and conductimetry were used on macroscopic foams to monitor the foam collapse under free drainage and small angle neutron scattering (SANS) at a given foam height allowed for the tracking of the evolution of film thickness under quasi-stationary conditions. Thin film pressure balance (TFPB) measurements enabled to quantify the resistance of single foam films to external pressure and to identify intra-film forces. At low SiW/surfactant ratios, the adsorption of SiW induces electrostatic repulsion within foam films. Above a concentration threshold corresponding to an adsorption saturation, excess of SiW screens the electrostatic repulsion that leads to thinner foam films. Despite screened electrostatics, the foam and single foam films remain very stable caused by an additional steric stabilizing force consistent with the presence of trapped micelles inside the foam films that bridge between the interfaces. These trapped micelles can serve as a surfactant reservoir, which promotes self-healing of the interface leading to much more resilient foam films in comparison to bare surfactant foams/films. [ABSTRACT FROM AUTHOR]

The structure–property studies in unpolymerized and polymerized tannic acid incorporated hydrogels exhibited the presence of micron sized aggregates. The hydrogen bonded aggregates breaks at high temperatures for the unpolymerized and polymerized cases as evident from the scattering studies. The structural changes is clearly reflected in rheological properties for the unpolymerized case as a clear elastic to dissipative transition while the polymerized case exhibited dissipation even at higher temperatures. [Display omitted] Hydrogels made with semi-interpenetrating networks of the oligomerized polyphenol tannic acid, and poly(acrylamide), exhibit high stiffness and toughness. However, the structure property relationships that give rise to enhanced mechanical properties is not well understood. Herein, we systematically investigate the hydrogels using small angle X-ray scattering and small and Ultra-small angle neutron scattering within a wide length scale range (1 nm to 20 µm), polarized optical microscopy, and rheology. Small angle X-ray and neutron scattering reveal the presence of micron sized hydrogen bonded clusters in the hydrogels. Breaking of hydrogen bonded clusters above a critical solution temperature was clearly observed in the small angle neutron scattering data. Polarized optical microscopy show enhanced anisotropy for the gels with oligomerized tannic acid incorporated - when compared to gels with monomeric tannic acid. Rheological studies at varying temperatures nicely corroborate the structural changes observed at high temperatures and reveal a self-healing behavior of the gels. The knowledge gained from this study will aid in rational design of hydrogels for biomedical applications. [ABSTRACT FROM AUTHOR]

The structure–property studies in unpolymerized and polymerized tannic acid incorporated hydrogels exhibited the presence of micron sized aggregates. The hydrogen bonded aggregates breaks at high temperatures for the unpolymerized and polymerized cases as evident from the scattering studies. The structural changes is clearly reflected in rheological properties for the unpolymerized case as a clear elastic to dissipative transition while the polymerized case exhibited dissipation even at higher temperatures. [Display omitted] Hydrogels made with semi-interpenetrating networks of the oligomerized polyphenol tannic acid, and poly(acrylamide), exhibit high stiffness and toughness. However, the structure property relationships that give rise to enhanced mechanical properties is not well understood. Herein, we systematically investigate the hydrogels using small angle X-ray scattering and small and Ultra-small angle neutron scattering within a wide length scale range (1 nm to 20 µm), polarized optical microscopy, and rheology. Small angle X-ray and neutron scattering reveal the presence of micron sized hydrogen bonded clusters in the hydrogels. Breaking of hydrogen bonded clusters above a critical solution temperature was clearly observed in the small angle neutron scattering data. Polarized optical microscopy show enhanced anisotropy for the gels with oligomerized tannic acid incorporated - when compared to gels with monomeric tannic acid. Rheological studies at varying temperatures nicely corroborate the structural changes observed at high temperatures and reveal a self-healing behavior of the gels. The knowledge gained from this study will aid in rational design of hydrogels for biomedical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Mixtures of hyaluronic acid (HA) with liposomes lead to hybrid colloid–polymer systems with a great interest in drug delivery. However, little is known about their microstructure. Small angle neutron scattering (SANS) is a valuable tool to characterize these systems in the semi-dilute entangled regime (1.5% HA) at high liposome concentration (80 mM lipids). The objective was to elucidate the influence of liposome surface (neutral, cationic, anionic or anionic PEGylated), drug encapsulation and HA concentration in a buffer mimicking biological fluids (37 °C). First, liposomes were characterized by SANS, cryo-electron microscopy, and dynamic light scattering and HA by SANS, size exclusion chromatography, and rheology. Secondly, HA-liposome mixtures were studied by SANS. In HA, liposomes kept their integrity. Anionic and PEGylated liposomes were in close contact within dense clusters with an amorphous organization. The center-to-center distance between liposomes corresponded to twice their diameter. A depletion mechanism could explain these findings. Encapsulation of a corticoid did not modify this organization. Cationic liposomes formed less dense aggregates and were better dispersed due to their complexation with HA. Liposome surface governed the interactions and microstructure of these hybrid systems. [ABSTRACT FROM AUTHOR]

[Display omitted] Mixtures of hyaluronic acid (HA) with liposomes lead to hybrid colloid–polymer systems with a great interest in drug delivery. However, little is known about their microstructure. Small angle neutron scattering (SANS) is a valuable tool to characterize these systems in the semi-dilute entangled regime (1.5% HA) at high liposome concentration (80 mM lipids). The objective was to elucidate the influence of liposome surface (neutral, cationic, anionic or anionic PEGylated), drug encapsulation and HA concentration in a buffer mimicking biological fluids (37 °C). First, liposomes were characterized by SANS, cryo-electron microscopy, and dynamic light scattering and HA by SANS, size exclusion chromatography, and rheology. Secondly, HA-liposome mixtures were studied by SANS. In HA, liposomes kept their integrity. Anionic and PEGylated liposomes were in close contact within dense clusters with an amorphous organization. The center-to-center distance between liposomes corresponded to twice their diameter. A depletion mechanism could explain these findings. Encapsulation of a corticoid did not modify this organization. Cationic liposomes formed less dense aggregates and were better dispersed due to their complexation with HA. Liposome surface governed the interactions and microstructure of these hybrid systems. [ABSTRACT FROM AUTHOR]

[Display omitted] Hypothesis: Saponins are a class of plant derived surfactants which are widely used in food related foams and emulsions, aerated drinks, and in pharmaceuticals and cosmetics. As a potential biosourced and renewable ingredient in a wider range of surfactant based formulations their potential is intimately associated with their mixing with synthetic surfactants. As such the nature of the mixed saponin-surfactant self-assembly is an important characteristic to investigate and understand. The unconventional structure of the saponins compared to the conventional synthetic surfactants poses some interesting constraints on the structures of the mixed aggregates. Experiments: Small angle neutron scattering, SANS, is used to investigate the structure of the saponin, escin, mixed with a range of nonionic surfactants with different ethylene oxide groups, from triethylene glycol monododecyl ether, C 12 E 3 , to dodecaethylene glycol monododecyl ether, C 12 E 12. Findings: The scattering data reveal a complex evolution in the solution self-assembled structure with varying escin / nonionic composition and ethylene oxide chain length. The rich structural development comprises of the evolution from the elongated micelle structure of escin to the micelle structure of the nonionic surfactant. At the intermediate solution compositions the structure is predominantly planar, comprising mostly of planar / micellar mixed phases. The nature of the planar structures depend upon the ethylene oxide chain length and the solution composition, and include lamellar, bilamellar vesicle, multilamellar vesicle, and nanovesicle structures, in common with what is observed in other surfactant mixtures. [ABSTRACT FROM AUTHOR]

[Display omitted] There is an increased interest in the use of natural surfactant as replacements for synthetic surfactants due to their biosustainable and biocompatible properties. A category of natural surfactants which are attracting much current interest is the triterpenoid saponins; surface active components found extensively in a wide range of plant species. A wide range of different saponin structures exist, depending upon the plant species they are extracted from; but regardless of the variation in structural details they are all highly surface active glycosides. Greater exploitation and application requires a characterisation and understanding of their basic adsorption and self-assembly properties. Glycyrrhizic acid, extracted from Licorice root, is a monodesmosidic triterpenoid saponin. It is widely used in cosmetic and pharmaceutical applications due to its anti-inflammatory properties, and is an ingredient in foods as a sweetener additive. It has an additional attraction due to its gel forming properties at relatively low concentrations. Although it has attracted much recent attention, many of its basic surface active characteristics, adsorption and self-assembly, remain relatively unexplored. How the structure of the Glycyrrhizic acid saponin affects its surface active properties and the impact of gelation on these properties are important considerations, and to investigate these are the focus of the study. In this paper the adsorption properties at the air–water interface and the self-assembly in solution have been investigated using by neutron reflectivity and small angle neutron scattering; in non-gelling and gelling conditions. The adsorption isotherm is determined in water and in the presence of gelling additives, and compared with the adsorption behaviour of other saponins. Gelation has minimal impact on the adsorption; apart from producing a rougher surface with a surface texture on a macroscopic length scale. Globular micelles are formed in aqueous solution with modest anisotropy, and are compared with the structure of other saponin micelles. The addition of gelling agents results in only minimal micelle growth, and the solutions remain isotropic under applied shear flow. [ABSTRACT FROM AUTHOR]

[Display omitted] Liquid lipid nanoparticles (LLN) are oil-in-water nanoemulsions of great interest in the delivery of hydrophobic drug molecules. They consist of a surfactant shell and a liquid lipid core. The small size of LLNs makes them difficult to study, yet a detailed understanding of their internal structure is vital in developing stable drug delivery vehicles (DDVs). Here, we implement machine learning techniques alongside small angle neutron scattering experiments and molecular dynamics simulations to provide critical insight into the conformations and distributions of the lipid and surfactant throughout the LLN. We simulate the assembly of a single LLN composed of the lipid, triolein (GTO), and the surfactant, Brij O10. Our work shows that the addition of surfactant is pivotal in the formation of a disordered lipid core; the even coverage of Brij O10 across the LLN shields the GTO from water and so the lipids adopt conformations that reduce crystallisation. We demonstrate the superior ability of unsupervised artificial neural networks in characterising the internal structure of DDVs, when compared to more conventional geometric methods. We have identified, clustered, classified and averaged the dominant conformations of lipid and surfactant molecules within the LLN, providing a multi-scale picture of the internal structure of LLNs. [ABSTRACT FROM AUTHOR]

Biomimetic liquid crystalline systems are widely used in skin care cosmetics and topical pharmaceutical preparations. Our ability to rationally design such formulations, however, is hampered by our incomplete understanding of their structure on the nanoscale. Using polarized light microscopy and small-angle and wide-angle X-ray scattering, the molecular architecture and properties of a barrier formulation prepared from distearoylphosphatidylcholine mixed with long chain fatty acid and alcohols, with and without antimicrobial pentanediols are directly probed. The nature and composition of the phases identified are determined through small-angle neutron scattering studies using chain-deuterated components, and the detailed structure and dynamics of the gel network lamellae are determined through molecular dynamics simulations. The formulations show molecular ordering with long and short periodicity lamellar phases and there is little change in these structures caused by changes in temperature, drying, or the application of shear stress. The diol-free formulation is demonstrated to be self-preserving, and the added pentanediols are shown to distribute within the interlamellar regions where they limit availability of water for microbial growth. In culmination of these studies, we develop a more complete picture of these complex biomimetic preparations, and thereby enable their structure-based design. [ABSTRACT FROM AUTHOR]

The adsorption of monoclonal antibodies (mAbs) on hydrophobic surfaces is known to cause protein aggregation and degradation. Therefore, surfactants, such as Poloxamer 188, are widely used in therapeutic formulations to stabilize mAbs and protect mAbs from interacting with liquid-solid interfaces. Here, the adsorption of Poloxamer 188, one mAb and their competitive adsorption on a model hydrophobic siliconized surface is investigated with neutron scattering coupled with contrast variation to determine the molecular structure of adsorbed layers for each case. Small angle neutron scattering measurements of the affinity of Poloxamer 188 to this mAb indicate that there is negligible binding at these solution conditions. Neutron reflectometry measurements of the mAb show irreversible adsorption on the siliconized surface, which cannot be washed off with neat buffer. Poloxamer 188 can be adsorbed on the surface already occupied by mAb, which enables partial removal of some adsorbed mAb by washing with buffer. The adsorption of the surfactant introduces significant conformational changes for mAb molecules that remain on the surface. In contrast, if the siliconized surface is first saturated with the surfactant, no adsorption of mAb is observed. Competitive adsorption of mAb and Poloxamer 188 from solution leads to a surface dominantly occupied with surfactant molecules, whereas only a minor amount of mAb absorbs. These findings clearly indicate that Poloxamer 188 can protect against mAb adsorption as well as modify the adsorbed conformation of previously adsorbed mAb. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are metal oxygen clusters with a range of interesting magnetic and catalytic properties. POMs with attached hydrocarbon chains show amphiphilic behaviour so we hypothesised that mixtures of a nonionic surfactant and anionic surfactants with a polyoxometalate cluster as headgroup would form mixed micelles, giving control of the POM density in the micelle, and which would differ in size and shape from micelles formed by the individual surfactants. Due to the high charge and large size of the POM, we suggested that these would be nonideal mixtures due to the complex interactions between the two types of surfactants. The nonideality and the micellar composition may be quantified using regular solution theory. With supplementary information provided by small-angle neutron scattering (SANS), an understanding of this unusual binary surfactant system can be established. A systematic study was performed on mixed surfactant systems containing polyoxometalate-headed amphiphiles (K 10 [P 2 W 17 O 61 OSi 2 (C n H 2n+1) 2 ], abbreviated as P 2 W 17 -2C n , where n = 12, 14 or 16) and hexaethylene glycol monododecyl ether (C 12 EO 6). Critical micelle concentrations (CMCs) of these mixtures were measured and used to calculate the interaction parameters based on regular solution theory, enabling prediction of micellar composition. Predictions were compared to micelle structures obtained from SANS. A phase diagram was also established. The CMCs of these mixtures suggest unusual unfavourable interactions between the two species, despite formation of mixed micelles. Micellar compositions obtained from SANS concurred with those calculated using the averaged interaction parameters for P 2 W 17 -2C n /C 12 EO 6 (n = 12 and 14). We attribute the unfavourable interactions to a combination of different phenomena: counterion-mediated interactions between P 2 W 17 units and the unfolding of the ethylene oxide headgroups of the nonionic surfactant, yet micelles still form in these systems due to the hydrophobic interactions between surfactant tails. [ABSTRACT FROM AUTHOR]

The work presents the characterization of Pluronic F127 micellar solutions in presence of hyaluronic acid in semi-dilute regime. The effects of the nature and salt concentration are investigated by differential scanning calorimetry and small angle neutron scattering. Hyaluronic acid reduces the critical micellar temperature to the same extend as an increase of the ionic strength. Within the investigated HA concentration range, the size and shape of the micelles are not modified by the addition of HA but their dispersion state depends on the salt concentration. By increasing the ionic strength we observe the formation of small micellar clusters which organize into a face-centered cubic liquid crystalline phase at high salt concentration. This behavior is reinforced by increasing the HA concentration or molecular weight. The nature of the salt plays also a role and divalent cations such as Ca2+ promote the clustering of micelles and their crystallization. The origin of the aggregative behavior is the change of the HA chain conformation –from stretched to coil- by addition of salt which in turn induces an excluded volume around the micelles and exerts a depletion interaction. [ABSTRACT FROM AUTHOR]

The ester sulfonate anionic surfactants are a potentially valuable class of sustainable surfactants. The micellar growth, associated rheological changes, and the onset of precipitation are important consequences of the addition of electrolyte and especially multi-valent electrolytes in anionic surfactants. Small angle neutron scattering, SANS, has been used to investigate the self-assembly and the impact of different valence electrolytes on the self-assembly of a range of ester sulfonate surfactants with subtly different molecular structures. The results show that in the absence of electrolyte small globular micelles form, and in the presence of NaCl, and AlCl 3 relatively modest micellar growth occurs before the onset of precipitation. The micellar growth is more pronounced for the longer unbranched and branched alkyl chain lengths. Whereas changing the headgroup geometry from methyl ester to ethyl ester has in general a less profound impact. The study highlights the importance of relative counterion binding strengths and shows how the surfactant structure affects the counterion binding and hence the micelle structure. The results have important consequences for the response of such surfactants to different operational environments. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Hypothesis The solvation characteristics of poly(ethylene oxide) (PEO) in nanostructured protic ionic liquids (PILs) are driven by polymer-solvent interactions in the polar domains of the PIL. This work hypothesises that the nanostructure of a PIL can be altered via halide addition, directly affecting the solvation of PEO. Experiments Small angle neutron scattering (SANS) is used to explore the conformation of 38 kDa PEO dissolved in the PIL propylammonium nitrate (PAN), a mol fraction of 10% propylammonium chloride (PACl) in PAN, and a mole fraction of 10% propylammonium bromide (PABr) in PAN. Findings Each of these solutions are shown to behave as a good solvent for PEO, as determined by their Flory exponents and Zimm plot analysis. The quality of solvation is reduced by the addition of the halide salt, with the order of solvation as follows: PAN > Br− addition > Cl− addition. Our experimental observations are consistent with the recently reported solvation structure of PEO in these solutions (Stefanovic et al., 2018). The increased charge density from NO 3 − to Br− to Cl− results in greater net ionic interaction between the ionic charge centres. As PEO interacts with PAN primarily through the ammonium hydrogens of the cation, this increased ionic interaction effectively displaces the PEO, resulting in poorer solvation. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Phytantriol is an interfacially-active lipid that is chemically robust, non-digestible and forms particles with internal bicontinuous cubic phase structures (cubosomes) when dispersed with non-ionic surfactants at ambient and physiological temperatures. The liquid crystalline internal structure of phytantriol-based cubosomes can be changed to alter the interfacial contact area/topology with the aqueous dispersant to trigger bioactive payload release or to alter the local membrane curvature around bound or embedded proteins. To enable the study of payload distribution, structure and transformation kinetics within phytantriol particles by neutron scattering techniques it is desirable to have access to a deuterated version of this molecule but to date a synthetic route has not been available. The first successful synthesis of phytantriol- d 39 is presented here alongside a preliminary physical characterisation of related particle structures when phytantriol- d 39 is dispersed using two non-ionic surfactants, Tween® 80 and Pluronic® F127. Synchrotron small angle X-ray scattering (SAXS) was used to confirm that phytantriol- d 39 -based nanoparticles in D 2 O form similar liquid crystalline structures to those of their natural isotopic abundance (phytantriol/H 2 O) counterparts as a function of temperature. Finally, small angle neutron scattering (SANS) with solvent contrast to match out the phytantriol- d 39 structuring was used to show that the spatial correlations between the Tween® and Pluronic® non-ionic surfactant molecules are different within dispersed phytantriol- d 39 particles with different liquid crystalline structures in D 2 O. The surfactant molecules in phytantriol- d 39 /Tween® 80 particles with Im 3 m cubic structures were found to follow a self-avoiding walk, whereas in phytantriol- d 39 /Pluronic® F127 particles with Pn 3 m cubic structures they were found to follow a more rod-like packing arrangement. [ABSTRACT FROM AUTHOR]

Hypothesis An effective way for fixating vesicle structures is the insertion of monomers and cross-linking agents into their bilayer, and their subsequent polymerization can lead to the formation of polymeric nanocapsules. Particularly attractive here are vesicle systems that form spontaneously well-defined small vesicles, as obtaining such small nanocapsules with sizes below 100 nm is still challenging. Experiments A spontaneously forming well-defined vesicle system composed of the surfactants TDMAO (tetradecyldimethylamine oxide), Pluronic L35, and LiPFOS (lithium perfluorooctylsulfonate) mixture was used as template for fixation by polymerization. Therefore, styrene monomer was incorporated into the vesicle bilayer and ultimately these structures were fixated by UV induced radical polymerization. Structural alteration of the vesicles upon loading with monomer and the cross-linker as well as the effect of subsequent polymerization in the membrane were investigated in detail by turbidity measurements, dynamic and static light scattering, (DLS, SLS), and small angle neutron scattering (SANS). Findings The analysis showed the changes on vesicle structures due to the monomer loading, and that these structures can become permanently fixed by the polymerization process. The potential of this approach to produce well-defined nanocapsules starting from a self-assembled system and following polymerization is critically evaluated. [ABSTRACT FROM AUTHOR]

In biomedical applications, PEGylation is frequently utilized to enhance the nanoparticles (NPs) capability for long systemic circulation times in the blood and it is also crucial to stabilize the NPs and thereby minimize their ability to agglomerate. In this study, we have synthesized poly( N -isopropylacrylamide) (PNIPAAM) nanogels with covalently attached PEG chains of different length and PEG coating densities. It is observed that in the absence of PEG coating the nanogels aggregate at elevated temperatures. It is found from dynamic light scattering (DLS) that both increased PEG length and enhanced PEG coating density have crucial influence on the stability of the nanogels. The results show that long PEG chains have a stronger impact on the shielding ability of the PEG layer on the nanogels than a high coating density of short chains. The small angle neutron scattering (SANS) measurements on PEG-coated nanogels indicate that the coated layer contract at higher temperatures but still the particles are stabilized. The bare PNIPAAM nanogels can be electrostatically stabilized by adding a small amount of an ionic surfactant. [ABSTRACT FROM AUTHOR]

Hypothesis The behavior/properties of micellar solutions are governed by Coulombic interactions that are influenced by the polarity of the surfactant head groups, hydrophobic tails, and solvent molecules. The addition of co-solvent should have a direct impact on solvent polarity and the size of the micelles are expected to decrease accordingly. Experiments In this study, a mixed surfactant system is studied composed of a common anionic surfactant, sodium laureth sulfate-1, modified by a zwitterionic surfactant, cocamidopropyl betaine in deuterated water. In this system, worm-like micelles (WLMs) are formed. The influence of a co-solvent, dipropylene glycol (DPG) in the present of high salt content, is investigated. DPG primarily modifies the dielectric constant of the solvent. Findings It was found that the addition of DPG slightly decreased the micelle radius, but dramatically reduced the persistence length as well as the contour length of the micelles. The relative dependence of contour length on salt concentration is not significantly changed. Thus, it is shown that the self-assembled structure can be tuned by adjusting solvent polarity without affecting the relative tunability of the WLM/ellipsoidal structure through counter ion concentration. [ABSTRACT FROM AUTHOR]

Hypothesis The conformation of poly(ethylene oxide) (PEO) in deep eutectic solvents (DESs) is determined by the polymer–solvent interactions, especially hydrogen bonding interactions. The hypothesis for this work is that the hydrogen bonding environment of a DES can be varied via changing the cation or hydrogen bond donor (HBD), and therefore the solvent quality for PEO; the anion species will also effect hydrogen bonding, but this is not examined here. Experiments Small angle neutron scattering (SANS) is used to probe the concentration dependent conformation of 36 kDa PEO dissolved in DESs formed by mixing ethyl or butyl ammonium bromide with a molecular HBD (glycerol or ethylene glycol) in a 1:2 molar ratio. Findings The radius of gyration ( R g ), Flory exponent and crossover concentration ( c * ) from the dilute to the semi-dilute regime of PEO in the DESs revealed by SANS and Zimm plot analysis show that these DESs are moderately good solvents for PEO. When the ammonium alkyl chain length is increased, the hydrogen bond density per unit volume decreases, and with it the solvent quality for PEO. The solvent quality is improved when the HBD is changed from glycerol to ethylene glycol due to differences in the hydrogen bonding environment for PEO. [ABSTRACT FROM AUTHOR]

The self-assembly of dilute aqueous solutions of a ternary surfactant mixture and rhamnolipid biosurfactant/surfactant mixtures has been studied by small angle neutron scattering. In the ternary surfactant mixture of octaethylene glycol monododecyl ether, C 12 E 8 , sodium dodecyl 6-benzene sulfonate, LAS, and sodium dioxyethylene monododecyl sulfate, SLES, small globular interacting micelles are observed over the entire composition and concentration range studied. The modelling of the scattering data strongly supports the assumption that the micelle compositions are close to the solution compositions. In the 5-component rhamnolipid/surfactant mixture of the mono-rhamnose, R1, di-rhamnose, R2, rhamnolipids with C 12 E 8 /LAS/SLES, globular micelles are observed over much of the concentration and composition range studied. However, for solutions relatively rich in rhamnolipid and LAS, lamellar/micellar coexistence is observed. The transition from globular to more planar structures arises from a synergistic packing in the 5 component mixture. It is not observed in the individual components nor in the ternary C 12 E 8 /LAS/SLES mixture at these relatively low concentrations. The results provide an insight into how synergistic packing effects can occur in the solution self-assembly of complex multi-component surfactant mixtures, and give rise to an unexpected evolution in the phase behaviour. [ABSTRACT FROM AUTHOR]

During lipolysis of triglyceride by lipase, monoglyceride and fatty acids are produced which combine with gastrointestinal fluids to form self-assembled structures. These solubilize hydrophobic food components to promote their absorption. The aim of this study was a detailed understanding of structure formation from triglyceride digestion products with saturated short-, medium- and long chain fatty acids. Complementary characterization methods have been applied comprising small angle X-ray and neutron scattering – the latter involving the contrast matching technique using fully deuterated fatty acids – polarized and depolarized dynamic light scattering and cryogenic-transmission electron microscopy. Shape, size and solubilization capacity of the self-assembled structures was dependent on composition and lipid chain length. Crystallization of fatty acid was observed when the solubility limit in the mixed bile salt micelles was exceeded; however, increasing pH and temperature increased the fatty acid solubility. The results provide insight into structure formation and crystallization of incorporated lipolysis products; this is important for a detailed understanding of food structure and nutrition, as well as the rational design of lipid based drug delivery systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] We study the formation of nanovesicles of cationic surfactant DEEDMAC. [•] A method to determine nanovesicle volume fraction is demonstrated. [•] The method is verified by neutron scattering measurements. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sodium dioctylsulfosuccinate+NaCl system studied in aqueous ethylene glycol (EG). [•] This surfactant exhibits special counterion binding behavior (SCB). [•] The SCB exists if the medium has cohesive energy density between 2.3 and 2.75Jm−3. [•] Change in the morphology of the surfactant aggregates is responsible for the SCB. [•] An anomalous deviation from the Corrin–Harkins equation observed when EG is⩾40%. [Copyright &y& Elsevier]

Highlights: [•] A skin friendly microemulsion could be made with technical grade components. [•] The obtained microemuslion follows the behavior known from model systems. [•] The enzyme DFPase still is active in this microemulsion despite the alcohol content. [•] The activity still is sufficiently high to be useful for skin decontamination. [Copyright &y& Elsevier]

Abstract: The changes in structure of high internal phase emulsions at low concentrations and at elevated temperature are reported for comparison with the same emulsions under conditions well away from instability. Small angle neutron scattering measurements on aqueous ammonium nitrate droplets dispersed in hexadecane and stabilized by very small quantities of a polyisobutylene-based surfactant (PIBSA) as well as related inverse micellar solutions in hexadecane, have been made as a function of temperature and surfactant concentration. Experimental conditions here favour larger and more deformable droplets than in previous studies. Besides the expected micelles and adsorbed surfactant, planar bilayers of micron lateral extent between touching droplets cover 20% of the droplet surface. Another difference from previous experiments is that the oil phase in the emulsions, and corresponding inverse micellar solutions are different in micellar radii and composition. The differences, and changes with surfactant concentration and temperature, are attributed to fractionation of the polydisperse PIBSA in the emulsions, but not the inverse micellar solutions. At low PIBSA concentration and high temperature the SANS shows emulsion decomposing into separate oil and aqueous phases. This occurs when the micelle concentration reaches a very small but measurable value. The inverse micelles may suppress by steric action long wavelength unstable capillary waves in the bilayers. Depletion repulsion forces here have a minor role in the emulsion stabilization. [Copyright &y& Elsevier]

Abstract: Encapsulation efficiencies of vesicles formed by the nonionic surfactant 1,2-dioctadecyl-rac-glycerol-3-ω-methoxydodecylethylene glycol (abbreviated as 2C18E12) and its phospholipid counterpart, distearoylphosphatidylcholine (DSPC) at 298 K, were determined by the entrapment of the water-soluble dye, carboxyfluorescein (CF) to be and L mol−1 for 2C18E12 vesicles prepared using low osmolarity (270 m Osm) Krebs–Henseleit (K–H) buffer and a modified ‘high salt’ (1600 m Osm) variant of K–H buffer, respectively, and and for DSPC vesicles prepared under the same conditions and in the same buffers. Freeze fracture electron microscopy studies confirmed the presence of vesicles when 2C18E12 and DSPC were dispersed in water and both buffer solutions. Small angle neutron scattering (SANS) studies, using D2O in place of H2O, showed that when 2C18E12 vesicles were prepared in the ‘high salt’ variant of K–H buffer as opposed to K–H buffer or water, a higher proportion of multilamellar vesicles (MLV) were formed. Furthermore when prepared in the ‘high salt’ variant of K–H buffer, the 2C18E12 bilayers were thinner, and when present in the form of MLV exhibited a smaller layer of water separating the bilayers. However, even in the absence of electrolyte, 2C18E12 formed surprisingly thin bilayers due to the penetration of the polyoxyethylene chains into the hydrophobic chain region of the bilayer. Due to the dehydrating effect of the high concentration of electrolyte present in the ‘high salt’ variant of K–H, the polyoxyethylene head groups penetrated further into the hydrophobic region of the bilayer making the bilayer even thinner. In the case of the DSPC vesicles, although the SANS study showed an increase in the relative proportion of multilamellar to unilamellar vesicles when samples were prepared in the ‘high salt’ variant of K–H buffer, no differences were observed in the thickness and the d-spacing of the vesicle bilayers. Variable temperature turbidity measurements of 2C18E12, and DSPC vesicles prepared in water indicated phase changes at and , respectively, and were unchanged when the ‘high salt’ variant of K–H buffer was used as hydrating medium. Taken together, these results suggest that a low phase transition temperature was not the reason for the poor entrapment efficiency of 2C18E12 vesicles but rather the very ‘thin’ hydrophobic barrier formed by the penetration of the polyoxyethylene chains into the hydrophobic region of the bilayer. [Copyright &y& Elsevier]

Abstract: Three new alkyl glycosides with similar molecular structures (oleyl and oleoyl alkyl chains and various head groups: disaccharide, trisaccharide and disaccharide with an additional amidoethoxy spacer) were synthesized and their supramolecular structure in aqueous solution was investigated. Small angle neutron scattering, surface tension measurement and the contact preparation method were applied to get molecular structure–property relationships. Although the chemical structures differ only in small details, their CMC values, lyotropic phase behaviour, surface area per surfactant molecule in the micelle and at the liquid–air interface, and the size and shape of the micelles are very different. We have found three different types of aggregates: spherical, cylindrical and polymer-like micelles in dilute solutions. [Copyright &y& Elsevier]

Abstract: Interactions between polycations and core–corona particles are governed by ion-exchange reactions, entropically favored by the release of counterions. This complexation process allows the chains to penetrate into the shell, leading to adsorbed amounts greater than 1 mg m-2. The destabilization occurs quickly, the domain of flocculation becomes larger when the concentration of monovalent salts is increased, and aggregates are composed of small and very compact clusters in a more or less self-similar structure at large scale. The adsorption of copolymers of low cationicity is characterized by still larger adsorbed amounts and layers thicker than the radius of gyration of the macromolecules. Depending on the charge content, the enhancement of the ionic strength can either promote the destabilization of the suspension or conversely induce the desorption of the chain. In pure water the structure of the flocs is long-range ordered and it becomes more heterogeneous in ionic media. [Copyright &y& Elsevier]

The structures of aggregates formed in aqueous solutions of an anionic surfactant, sodium dodecyl sulfate (SDS), with the addition of a cationic hydrotropic salt, p-toluidine hydrochloride (PTHC), have been investigated by small angle neutron scattering (SANS). The SANS spectra exhibit a pronounced peak at low salt concentration, indicating the presence of repulsive intermicellar interactions. Model-independent real space information about the structure is obtained from a generalized indirect Fourier transformation (GIFT) technique in combination with a suitable model for the interparticle structure factor. The interparticle interaction is captured using the rescaled mean spherical approximation (RMSA) closure relation and a Yukawa form of the interaction potential. Further quantification of the geometrical parameters of the micelles was achieved by a complete fit of the SANS data using a prolate ellipsoidal form factor and the RMSA structure factor. The present study shows that PTHC induces a decrease in the fractional charge of the micelles due to adsorption at the micellar surface and consequent growth of the SDS micelles from nearly globular to rodlike as the concentration of PTHC increases. [Copyright &y& Elsevier]