The Relationship between Wormlike Micelle Scission Free Energy and Micellar Composition: The Case of Sodium Lauryl Ether Sulfate and Cocamidopropyl Betaine

Wand, Charlie R.; Panoukidou, Maria; Regno, Annalaura Del; Anderson, R. L.; Carbone, Paola

doi:10.1021/acs.langmuir.0c02210

Cited by 19 publications

(22 citation statements)

References 64 publications

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“…Free in solution, zwitterionic micelles are additionally subject to strong hydration repulsion which opposes close proximity and thereby hinders rapid coalescence of micelles via consecutive fusion events. Hence, the end cap free energy and concomitant scission barrier derived in molecular simulations via free energy calculations (e.g., citations [60,61]) rather reflects an intrinsic free energy which may not trivially translate into the expected size distribution free in solution.…”

Section: Discussionmentioning

confidence: 99%

Where are those lipid nano rings?

Endter

Risselada

2021

Journal of Colloid and Interface Science

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Highly curved toroidal micelles with diameters as small as 100 nm have been successfully constructed by self-assembly of amphiphilic block copolymers. These structures may have potential applications in gene or drug delivery. Experimental observations suggest that toroidal micelles likely originate from spherical or disc-like micelles which are tricked into forming toroidal micelles upon external stimuli ('smart' materials). Since self-assembly of polymeric and lipid surfactants is guided by the same physical principles, we hypothesize that 'smart' lipid surfactants can be equivalently tricked into forming highly curved toroidal micelles that are tenfold smaller ('10 nm diameter). Paradoxically, these 'nano rings' have never been observed. Using coarse-grained molecular dynamics (MD) simulations in conjunction with a state-ofthe-art free energy calculation method (a string method), we illustrate how a thermo-responsive lipid surfactant is able to form toroidal micelles. These micelles originate from disc-like micelles that are spontaneously perforated upon heat shocking, thereby supporting a longstanding hypothesis on the possible origin of polymeric toroidal micelle phases observed in experiments. We illustrate that kinetically stable 'nano rings' are substantially shorter lived than their tenfold larger polymeric analogs. The estimated lifetime (milliseconds) is in fact similar to the characteristic breaking time of the corresponding worm-like micelle. Finally, we resolve the characteristic finger print which 'nano rings' leave in time-resolved X-ray spectra and illustrate how the uptake of small DNA fragments may enhance their stability. Despite a shared kinetics of self-assembly, length scale dependent differences in the life-time of surfactant phases can occur when phases are kinetically rather than thermodynamically stable. This results in the apparent absence or presence of toroidal micelle phases on different length scales. Our theoretical work precisely illustrates that the universality of surfactants nevertheless remains conserved even at different length scales.

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Section: Discussionmentioning

confidence: 99%

Where are those lipid nano rings?

Endter

Risselada

2021

Journal of Colloid and Interface Science

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“…The above considerations have motivated a significant renewed interest in modeling surfactants. − In our work, we have developed coarse-grained dissipative particle dynamics (DPD) models with explicit chemical specificity, which we have shown can accurately reproduce the CMCs of pure nonionic and anionic materials. Now we turn to the challenging problem of using these methods to predict the behavior of surfactant mixtures and blends.…”

Section: Introductionmentioning

confidence: 99%

Critical Micelle Concentrations in Surfactant Mixtures and Blends by Simulation

et al. 2021

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We explore the use of coarse-grained dissipative particle dynamics simulations to predict critical micelle concentrations (CMCs) in polydisperse surfactant mixtures and blends. By fitting pseudo-phase separation models (PSMs) to aqueous solutions of binary surfactant mixtures at selected compositions above the CMC, we avoid the need for expensive simulations of more complex multicomponent mixtures performed as a function of dilution. The approach is demonstrated for sodium laureth sulfate (SLES) surfactants with polydispersity in the ethoxylate spacer. For this system, we find a modest degree of cooperativity in micelle formation, which we attribute to the reduced repulsion between charged headgroups for surfactants with dissimilar ethoxylate spacer lengths. However, this is insufficient to explain the lowered CMC often observed in commercial SLES samples, which we attribute to the presence of small amounts of unsulfated alkyl ethoxylates and/or traces of salt.

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“…Dissipative Particle Dynamics (DPD) is a mesoscopic method widely used to predict the morphology of complex fluids in both toy models [1][2][3] and systematically parametrized models for specific chemical systems [4][5][6][7] . Despite its popularity to quickly scan large shallow energy surfaces, the ability of DPD to predict dynamical properties (e.g.…”

Section: Introductionmentioning

confidence: 99%