Structural Evolution of Wormlike Micellar Fluids Formed by Erucyl Amidopropyl Betaine with Oil, Salts, and Surfactants

Shear layers and plugs in the capillary flow of wormlike micellar gels

Wormlike micellar solutions formed by long-chained zwitterionic surfactants show gel-like rheology at room temperature and have recently been found to exhibit other complex and interesting rheological features. We study the dynamics of these wormlike micellar gels in a pipe-flow scenario using particle imaging and tracking velocimetry and report the existence of plug flows with strong wall slip and non-parabolic velocity profiles for different surfactant concentrations and imposed flow rates. We rationalize these results as features of a developing transient flow of a viscoelastic solution in space and time. We show that evolution of shear layers is governed by intermittent flows, asymmetric velocity profiles and flow induced heterogeneity. Our experiments shed light on the transient fluid dynamics of wormlike micelles in simple geometries and highlight the complexity of flows involving wormlike micellar gels and similar soft matter systems in canonical flows.

Wormlike micellar solutions formed by an anionic surfactant and a cationic surfactant with two head groups

Innovation in the molecular structure of surfactants is important for the preparation of soft materials with novel properties. In this study, we synthesized a cationic surfactant, N1,N1,N1,N1,N3,N3,N3-pentamethyl-N3-(3-stearamidopropyl)propane-1,3-diammonium bromide, hereafter referred to as C18-DQA. Unlike conventional cationic surfactants, C18-DQA contains two quaternary ammonium head groups and a long-saturated alkyl chain equal to a chain length of 21 carbon atoms. C18-DQA exhibits a low Krafft point of ∼0 °C and a water solubility >1000 mM at 25 °C. The critical micelle concentration (cmc) of C18-DQA was determined to be 0.59 mM using the Nile red method. C18-DQA was mixed with sodium laurate (SL) at different molar ratios to produce transparent solutions with excellent viscoelasticity over a wide concentration range. The 1 : 1.5 molar ratio C18-DQA/SL mixed solutions exhibited gel-like behavior for a total surfactant concentration of 2.88 wt% (75 mM). The solution with a total surfactant concentration of 300 mM (120 mM C18-DQA and 180 mM SL) achieved a maximum zero-shear viscosity (η0) of 4224 Pa s. Cryogenic transmission electron microscopy analysis revealed the formation of extremely long wormlike micelles, with a cross-sectional diameter of 5 nm and contour length >3 μm, in the mixed solutions. C18-DQA and SL molecules were drawn close by electrostatic attractions, leading to a suitable molecular geometry for the extensive growth of wormlike micelles. This work will act as an important reference for the future preparation of highly viscoelastic solutions by mixing cationic and anionic surfactants. The proposed system is also expected to have potential applications in cosmetic formulations, home care products, and oilfield fracturing fluids.

Influence of tail group length, amide functionality and added salt ion identity on the behaviour of betaine surfactants

Hypothesis The behaviour of surfactants in solution and at interfaces is governed by a combination of steric and electrostatic effects experienced by surfactant molecules as they interact with solvent, other species in solution, and each other. It would therefore be anticipated that highly interacting groups would significantly influence surfactant behaviour. The widely used amide functionality has polar H-bond donor/acceptor properties, and therefore its inclusion into a surfactant structure should have a profound effect on surface activity and self-assembly of that surfactant when compared to the equivalent molecule without an amide linker. Further, chaotropic or kosmotropic salt ions that affect water structuring and hydrogen bonding may provide opportunities for further tuning surfactant interactions in such cases. Experiments A library of betaine surfactant with tail lengths n=14-22 both with and without an amidopropyl linker were synthesised to study the effect of the amide functionality on surfactant properties. Characterisation of the molecules interfacial properties were performed using pendant drop tensiometry and their solution state formulation properties were probed using small-angle neutron scattering (SANS) and rheological measurements. Findings Presence of an amidopropyl linker had little effect on aggregation propensity (as evidenced by critical micelle concentration) and aggregate morphology of betaine surfactants, but did increase the Krafft temperature of these surfactants. SANS analysis indicated that aggregate morphology of alkyl betaine surfactants could be influenced by the addition of sodium salts with chaotropic counterions (I- and SCN-), but they were insensitive to more kosmotropic anions (SO42-, F- and Cl-), providing unique and novel solution control methods for this (supposedly salt-insensitive) class of surfactants.

Parabolic Viscosity Behavior of NaCl-Thickened Surfactant Systems upon Temperature Change

The viscosity of household care products plays an important role in pleasant delivery using consumer experience at home. A novel solution to mitigate the sharp rising of viscosities at low temperatures of detergents was proposed. By designing the formulation of the surfactant blend, formulators can achieve acceptable viscosity profiles in the temperature range encountered in daily life. The verification and modulation of formulas bearing parabolic viscosity-temperature behavior were systematically studied, including in single, binary, and ternary systems, based on the modulation of sodium ethoxylated alkyl sulfate (AES) by other anions, zwitterions, and nonions. The R ratio theory was used to have a better understanding of the molecular assembly of surfactants behind the parabolic behavior exhibited in rheology analyses. One of the key findings is that the parabolic viscosity-temperature phenomenon could be easily observed in the highly hydrated ethoxylated anionic systems like AES-based systems. For those anions lacking ethoxylation, especially sodium linear alkylbenzene sulfonate (LAS), the monotonic variation of hydration affinity with temperature led to the disappearance of parabola in the observed temperature window (>0 °C). Moreover, salinity played an important role in the hydration affinity of the polar group and the interaction between the hydrophilic headgroups. A balanced salinity should be optimized to modulate the hydration affinity in a desired range so that the parabola could be easily tuned within the target temperature region. These findings provide opportunities for the formulators in the household care industry to design products with better pourability through carefully selecting a combination of surfactants and fine-tuning their ratios to improve consumer use experience, especially in winter.

A Comparative Study on CO2-Switchable Foams Stabilized by C22- or C18-Tailed Tertiary Amines

The CO2 aqueous foams stabilized by bioresource-derived ultra-long chain surfactants have demonstrated considerable promising application potential owing to their remarkable longevity. Nevertheless, existing research is still inadequate to establish the relationships among surfactant architecture, environmental factors, and foam properties. Herein, two cases of ultra-long chain tertiary amines with different tail lengths, N-erucamidopropyl-N,N-dimethylamine (UC22AMPM) and N-oleicamidopropyl-N,N-dimethylamine (UC18AMPM), were employed to fabricate CO2 foams. The effect of temperature, pressure and salinity on the properties of two foam systems (i.e., foamability and foam stability) was compared using a high-temperature, high-pressure visualization foam meter. The continuous phase viscosity and liquid content for both samples were characterized using rheometry and FoamScan. The results showed that the increased concentrations or pressure enhanced the properties of both foam samples, but the increased scope for UC22AMPM was more pronounced. By contrast, the foam stability for both cases was impaired with increasing salinity or temperature, but the UC18AMPM sample is more sensitive to temperature and salinity, indicating the salt and temperature resistance of UC18AMPM-CO2 foams is weaker than those of the UC22AMPM counterpart. These differences are associated with the longer hydrophobic chain of UC22AMPM, which imparts a higher viscosity and lower surface tension to foams, resisting the adverse effects of temperature and salinity.

Wormlike micelles of CTAB with phenols and with the corresponding phenolate derivatives - When hydrophobicity and charge drive the coacervation

HYPOTHESIS

Hydrophobicity and the presence or absence of charge in phenol derivatives are relevant on the rheology and phase behavior when they are assembled with a cationic surfactant, forming wormlike micelles. The incorporation of phenols with a greater number of rings into the micellar palisade is entropically favored, but a solubilization limit or coacervation are two paths followed by the solutions, depending on the electrical nature of the aromatic co-solutes.

EXPERIMENTS

The investigations were carried out with systems formed by a fixed concentration of hexadecyltrimethylammonium bromide (CTAB) and increasing concentrations of neutral phenols (1-naphthol, 2-naphthol, 2,3-dihydroxynaphthalene and R and S-binol) and with their corresponding phenolate derivatives. The monophasic limits of the systems were established, as well as their linear and non-linear rheology. The structural investigation of the coacervates formed with the phenolates were done using SAXS and Cryo-TEM.

FINDINGS

The zero-shear viscosity of the solutions reaches maxima values close to the solubility limit of the aromatics, which depends on the numbers of rings and hydroxyl groups (position and number). However, when the correspondent ionized phenols were investigated, beyond the maxima values for the zero-shear viscosity, liquid-liquid biphasic systems are formed, in which the upper phase contains a coacervate, associated with branched wormlike micelles. However, when the ratio between phenolate and CTAB is around 3:1 the coacervate evolves to a lamellar structure.

Structure-Performance Relationships for Tail Substituted Zwitterionic Betaine-Azobenzene Surfactants

Azobenzene-containing surfactants (azo-surfactants) have garnered significant attention for their use in generating photoresponsive foams, interfaces, and colloidal systems. The photoresponsive behavior of azo-surfactants is driven by the conformational and electronic changes that occur when the azobenzene chromophore undergoes light-induced trans ⇌ cis isomerization. Effective design of surfactants and targeting of their properties requires a robust understanding of how the azobenzene functionality interacts with surfactant structure and influences overall surfactant behavior. Herein, a library of tail substituted azo-surfactants were synthesized and studied to better understand how surfactant structure can be tailored to exploit the azobenzene photoswitch. This work shows that tail group structure (length and branching) has a profound influence on the critical micelle concentration of azo-surfactants and their properties once adsorbed to an air-water interface. Neutron scattering studies revealed the unique role that intermolecular π-π azobenzene interactions have on the self-assembly of azo-surfactants, and how the influence of these interactions can be tuned using tail group structure to target specific aqueous aggregate morphologies.

Spontaneous surface adsorption of aqueous graphene oxide by synergy with surfactants

The spontaneous adsorption of graphene oxide (GO) sheets at the air-water interface is explored using X-ray reflectivity (XRR) measurements. As a pure aqueous dispersion, GO sheets do not spontaneously adsorb at the air-water interface due to their high negative surface potential (-60 mV) and hydrophilic functionality. However, when incorporated with surfactant molecules at optimal ratios and loadings, GO sheets can spontaneously be driven to the surface. It is hypothesised that surfactant molecules experience favourable attractive interactions with the surfaces of GO sheets, resulting in co-assembly that serves to render the sheets surface active. The GO/surfactant composites then collectively adsorb at the air-water interface, with XRR analysis suggesting an interfacial structure comprising surfactant tailgroups in air and GO/surfactant headgroups in water for a combined thickness of 30-40 Å, depending on the surfactant used. Addition of too much surfactant appears to inhibit GO surface adsorption by saturating the interface, and low loadings of GO/surfactant composites (even at optimal ratios) do not show significant adsorption indicating a partitioning effect. Lastly, surfactant chemistry is also a key factor dictating adsorption capacity of GO. The zwitterionic surfactant oleyl amidopropyl betaine causes marked increases in GO surface activity even at very low concentrations (≤0.2 mM), whereas non-ionic surfactants such as Triton X-100 and hexaethyleneglycol monododecyl ether require higher concentrations (ca. 1 mM) in order to impart spontaneous adsorption of the sheets. Anionic surfactants do not enhance GO surface activity presumably due to like-charge repulsions that prevent co-assembly. This work provides useful insight into the synergy between GO sheets and molecular amphiphiles in aqueous systems for enhancing the surface activity of GO, and can be used to inform system formulation for developing water-friendly, surface active composites based around atomically thin materials.

Heads or tails? The synthesis, self-assembly, properties and uses of betaine and betaine-like surfactants

Betaines are a key class of zwitterionic surfactant that exhibit particularly favorable properties, making them indispensable in modern formulation. Due to their composition, betaines are readily biodegradable, mild on the skin and exhibit some antimicrobial activity. Vital to their function, these surfactants self-assemble into diverse micellar geometries, some of which contribute to increased solution viscosity, and their surface activity results in strong detergency and foaming. As such, their behavior has been exploited in various applications from personal care (including shampoos and liquid soaps) to specific industrial fields (such as enhanced oil recovery). This review aims to inform the reader of the diverse range of different betaine and betaine-like surfactants that have been actively researched over the past three decades. Synthesis as well as both chemical and physical characterization of betaine surfactants are discussed, including small-angle scattering studies that indicate self-assembly structures and rheological data that demonstrates texture and flow. Stimulus responsive systems and exotic betaine analogs with enhanced functionality are also covered. Crucially, the connection between surfactant molecular architecture and function are highlighted, exemplifying precisely why zwitterionic betaine and related surfactants are so uniquely functional.

Deducing the Relation between Viscosity and Oil-Induced Structural Changes of Viscoelastic Surfactants Using a Kinetic Approach

The present study relates viscosity reduction with time of a wormlike micellar solution to the micellar transitions that occur with time in the presence of three n-alkanes, namely, n-decane, n-dodecane, and n-hexadecane. Steady-shear rheology and small-angle X-ray scattering were used to deduce the relationship. The effect of n-alkane concentration was tested only with n-decane. There were at most three stages of viscosity reduction, which appeared in the following order: (i) the rising viscosity stage, (ii) the fast viscosity reduction stage, and (iii) the low-viscosity stage. The stages and rates of viscosity transition depended on the type of micelles present and the degree of micelle entanglement. Moreover, the rate of transition increased when the n-alkane concentration was increased and when the n-alkane molecular mass was reduced. n-Hexadecane induced only the first two stages of transition at a slower rate compared to the other oils.

Molecular Basis for the Morphological Transitions of Surfactant Wormlike Micelles Triggered by Encapsulated Nonpolar Molecules

Surfactant wormlike micelles are prone to experience morphological changes, including the transition to spherical micelles, upon the addition of nonpolar additives. These morphological transitions have profound implications in diverse technological areas, such as the oil and personal-care industries. In this work, additive-induced morphological transitions in wormlike micelles were studied using a molecular theory that predicts the equilibrium morphology and internal molecular organization of the micelles as a function of their composition and the molecular properties of their components. The model successfully captures the transition from wormlike to spherical micelles upon the addition of a nonpolar molecule. Moreover, the predicted effects of the concentration, molecular structure, and degree of hydrophobicity of the nonpolar additive on the wormlike-to-sphere transition are shown to be in good agreement with experimental trends in the literature. The theory predicts that the location of the additive in the micelle (core or hydrophobic-hydrophilic interface) depends on the additive hydrophobicity and content, and the morphology of the micelles. Based on the results of our model, simple molecular mechanisms were proposed to explain the morphological transitions of wormlike micelles upon the addition of nonpolar molecules of different polarities.

Spontaneous Self-Assembly of Thermoresponsive Vesicles Using a Zwitterionic and an Anionic Surfactant

Spontaneous formation of vesicles from the self-assembly of two specific surfactants, one zwitterionic (oleyl amidopropyl betaine, OAPB) and the other anionic (Aerosol-OT, AOT), is explored in water using small-angle scattering techniques. Two factors were found to be critical in the formation of vesicles: surfactant ratio, as AOT concentrations less than equimolar with OAPB result in cylindrical micelles or mixtures of micellar structures, and salt concentration, whereby increasing the amount of NaCl promotes vesicle formation by reducing headgroup repulsions. Small-angle neutron scattering measurements reveal that the vesicles are approximately 30-40 nm in diameter, depending on sample composition. Small-angle X-ray scattering measurements suggest preferential partitioning of OAPB molecules on the vesicle inner layer to support vesicular packing. Heating the vesicles to physiological temperature (37 °C) causes them to collapse into smaller ellipsoidal micelles (2-3 nm), with higher salt concentrations (≥10 mM) inhibiting this transition. These aggregates could serve as responsive carriers for loading or unloading of aqueous cargoes such as drugs and pharmaceuticals, with temperature changes serving as a simple release/uptake mechanism.

Real-time monitoring of oil-induced micellar transitions in viscoelastic surfactants by small-angle X-ray scattering

HYPOTHESIS

Viscoelastic surfactant solutions with entangled wormlike micelles (WLMs) display dramatic changes in rheological properties when exposed to hydrophobic substances. This change is key in the oil and gas industry and for drug delivery. The changes in viscoelastic properties are believed to be a result of changes in micellar shape due to the oil solubilization. The time dependence of the process has practical importance, yet its mechanism is unknown. We set out to map the structural changes with time using small-angle x-ray scattering (SAXS).

EXPERIMENT

A surfactant system with erucamidopropyl hydroxypropyl sulfobetaine as the active ingredient was homogenized with three concentrations of n-decane (70 mM, 140 mM, 280 mM) in 600 mM CaCl₂. The samples were monitored with time using SAXS. Model fits were used to determine the structures present in the sample at each time interval.

FINDINGS

The entangled WLMs disappeared while spherical decane-swollen micelles formed with time, explaining the sharp decrease in viscosity. It was shown that the time at which the spherical swollen micelles appeared depends on the concentration of n-decane. This insight allows control of the spherical micelle appearance time, which is important for the successful application of WLMs in sectors that require WLMs to persist for a set time before they transform.

Predicting the effect of additives on wormlike micelle and liquid crystal formation and rheology with phase inversion phenomena

HYPOTHESIS

Surfactant-based viscoelastic fluids are used in consumer products such as body wash, cosmetics, and in hydraulic fracturing fluids to suspend proppant, among others. The solubilization of oil within these fluids changes the curvature of the surfactant and their nanostructure and rheological properties. The curvature-based hydrophilic-lipophilic-difference + net-average-curvature (HLD-NAC) framework may be able to quantify curvature changes and predict the formulation conditions required to obtain viscoelasticity.

EXPERIMENTS

Phase inversion experiments were conducted for combinations of commercial-grade C₈, C₁₀ and C₁₂ tetrapropylene glycol ether sulfate (extended) surfactant and sodium dihexyl sulfosuccinate with oil to obtain the HLD-NAC parameters. Wormlike micelles (WLMs) and liquid crystals (LCs) were then formulated and characterized. The transition from spherical micelles to WLMs/LCs at different oil contents was identified and compared with phase transitions predicted via the HLD-NAC model.

FINDINGS

The spherical micelle to branched WLM/LC transition in surfactant + oil systems coincided with the water-continuous (Type I) to bicontinuous (Type III) microemulsion phase transition predicted with the HLD-NAC model. Using this finding, the transition of commercial-grade sodium laureth sulfate (SLES) micelles to viscoelastic LCs containing various oils was predicted using the HLD-NAC. The HLD-NAC also predicted the presence of a secondary peak in viscosity obtained in "salt curves" experiments associated with branched WLMs and LCs.

Oil-Induced Viscoelasticity in Micellar Solutions of Alkoxy Sulfate

Rheological properties of the solution of an extended surfactant, sodium alkoxy sulfate (C₈-(PO)₄-(EO)₁-SO₄Na), are investigated as a function of the presence of various paraffinic oils over a range of salt conditions in the Winsor III microemulsion region at oil fractions where the microemulsion is "oil-starved". The addition of as small as 3 vol % alkane to 2 wt % surfactant solutions at salt concentrations where the oil-water interfacial tension is minimized induces a sudden shift in the rheological behavior. The solution viscosity increases by 5 orders of magnitude, with solid-like behaviors (G' > G″) being observed in the entire frequency region investigated (0.01-100 rad/s). Commonly, in the cases where wormlike micelles are present in the solution, alkanes are believed to be solubilized in the core of micelles, leading to a radial growth of the cylindrical part of the wormlike micelle, resulting in a drop of end-cap energy (E_C) and micelle length and a reduction in viscosity. In this study, however, the addition of oil causes the formation of wormlike micelles. The viscosity of solubilized-oil samples does, however, decrease with an increase in incorporated oil volume. We hypothesize that this "abnormal oleo-responsive" viscoelastic behavior is related to a spacer of intermediate hydrophilicity, that is, polypropylene oxide (PO) segment of the alkoxy sulfate, being inserted between the hydrophobic tail and hydrophilic head (the ethoxylated sulfate segment) of the extended surfactant. The addition of a small amount of oil likely extends the PO moiety and increases the tail length of the surfactant in the aggregates as well as reducing the headgroup size, driving the formation of wormlike micelles from a solution that initially had a viscosity consistent with the absence of such structures.

Probing the dynamic self-assembly behaviour of photoswitchable wormlike micelles in real-time

Understanding the dynamic self-assembly behaviour of azobenzene photosurfactants (AzoPS) is crucial to advance their use in controlled release applications such as drug delivery and micellar catalysis. Currently, their behaviour in the equilibrium cis- and trans-photostationary states is more widely understood than during the photoisomerisation process itself. Here, we investigate the time-dependent self-assembly of the different photoisomers of a model neutral AzoPS, tetraethylene glycol mono(4',4-octyloxy,octyl-azobenzene) (C8AzoOC8E4) using small-angle neutron scattering (SANS). We show that the incorporation of in situ UV-Vis absorption spectroscopy with SANS allows the scattering profile, and hence micelle shape, to be correlated with the extent of photoisomerisation in real-time. It was observed that C8AzoOC8E4 could switch between wormlike micelles (trans native state) and fractal aggregates (under UV light), with changes in the self-assembled structure arising concurrently with changes in the absorption spectrum. Wormlike micelles could be recovered within 60 seconds of blue light illumination. To the best of our knowledge, this is the first time the degree of AzoPS photoisomerisation has been tracked in situ through combined UV-Vis absorption spectroscopy-SANS measurements. This technique could be widely used to gain mechanistic and kinetic insights into light-dependent processes that are reliant on self-assembly.

Oil-induced formation of branched wormlike micelles in an alcohol propoxysulfate extended surfactant system

The addition of oil to an extended surfactant-water system (sodium tetrapropylene glycol (2-ethyl)octyl ether sulfate, C₁₀PO₄SO₄Na) induces the elongation of spherical micelles into oil-swollen branched wormlike micelles (WLMs) near the phase inversion point of the surfactant-oil-water (SOW) system. The hydrophilic-lipophilic-difference (HLD) framework, which has been associated with surfactant curvature, was successfully used to predict the conditions under which WLMs are produced for both polar and non-polar oils. At HLD = 0, the formation of low-curvature surfactant structures including WLMs and liquid crystals are favored in water-rich systems. Micellar growth begins around HLD = -0.5, and reaches a plateau upon the formation of a branched WLM network at HLD = 0. Above the entanglement concentration, the branched WLMs exhibit Maxwell and shear thinning behavior which is suitable for the suspension of nanoparticles, among others.

Design and performance of the variable-wavelength Bonse–Hart ultra-small-angle neutron scattering diffractometer KOOKABURRA at ANSTO

The double-crystal ultra-small-angle neutron scattering (USANS) diffractometer KOOKABURRA at ANSTO was made available for user experiments in 2014. KOOKABURRA allows the characterization of microstructures covering length scales in the range of 0.1–10 µm. Use of the first- and second-order reflections coming off a doubly curved highly oriented mosaic pyrolytic graphite premonochromator at a fixed Bragg angle, in conjunction with two interchangeable pairs of Si(111) and Si(311) quintuple-reflection channel-cut crystals, permits operation of the instrument at two individual wavelengths, 4.74 and 2.37 Å. This unique feature among reactor-based USANS instruments allows optimal accommodation of a broad range of samples, both weakly and strongly scattering, in one sample setup. The versatility and capabilities of KOOKABURRA have already resulted in a number of research papers, clearly demonstrating that this instrument has a major impact in the field of large-scale structure determination.

Self-Assembly of Long-Chain Betaine Surfactants: Effect of Tailgroup Structure on Wormlike Micelle Formation

Long-chain amidopropyl betaines are known for their ability to self-assemble into viscoelastic wormlike micellar structures. Here, we explore the effect of tailgroup molecular architecture on this process, comparing five molecules, each with C18 chains but different levels of unsaturation and branching. The surfactants are synthesized from stearic, oleic, linoleic, linolenic, and isostearic acids. The self-assembly of these molecules in aqueous solutions is explored using small- and ultra-small-angle neutron scattering (SANS and USANS). It is seen that optimum wormlike micelle formation is achieved for the oleic-chained surfactant, and the alignment of self-assembled structures is further explored using rheo-SANS. The more highly unsaturated molecules form rodlike micelles, whereas the stearic-tailed molecule shows a pronounced Krafft point and the isostearic-chained surfactant is entirely water-insoluble. These results demonstrate the critical importance of tailgroup geometry on surfactant properties and self-assembly for this industrially important class of surfactants.

Bulk properties of aqueous graphene oxide and reduced graphene oxide with surfactants and polymers: adsorption and stability

Aqueous dispersions of graphene oxide and reduced graphene oxide are combined with carefully chosen surfactants and polymers to investigate adsorption and bulk properties in these systems.

Photoswitchable Janus glycodendrimer micelles as multivalent inhibitors of LecA and LecB from Pseudomonas aeruginosa

The first example of the self-assembly and lectin binding properties of photoswitchable glycodendrimer micelles is reported. Light-addressable micelles were assembled from a library of 12 amphiphilic Janus glycodendrimers composed of variable carbohydrate head groups and hydrophobic tail groups linked to an azobenzene core. Spontaneous association in water gave cylindrical micelles with uniform size distribution as determined by dynamic light scattering (DLS) and small angle neutron scattering (SANS). Trans-cis photoisomerization of the azobenzene dendrimer core was used to probe the self-assembly behaviour and lectin binding properties of cylindrical micelles, revealing moderate-to-potent inhibition of lectins LecA and LecB from Pseudomonas aeruginosa.