On the Shape and Rheology of Linear Micelles in Dilute Solutions

Carl, Wilfried; Makhloufi, R.; Kröger, Martin

doi:10.1051/jp2:1997163

Cited by 22 publications

(42 citation statements)

References 2 publications

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“…3 we compare equilibrium ͑␥ =0͒ and sheared ͑␥ =1͒ size distributions for = 1 and E sc = 8.09 k B T. Under shear flow, the probability of encountering a linear chain of a particular size decreases, relative to that probability in the quiescent state, for all chain sizes except for very small chains. Also, the average linear-chain size decreases with increasing shear rate, in agreement with previous observations in simulations of wormlike micelles [11,12]. Interestingly, the probability to encounter a ring of a particular size is found to increase for a wide range of ring sizes, from the smallest rings allowed ͑L c ͒ up to relatively large rings of order 100 monomers (which is much larger than the average ring size).…”

Section: A Distribution and Average Sizesupporting

confidence: 89%

“…However, after this reduction, an additional tension (compared to equilibrium) remains in the bonds, associated with a larger momentum transfer. This leads to the observed decrease of the average length of linear chains [12]. The dependence of the average ring size on shear rate is quite different.…”

Section: A Distribution and Average Sizementioning

confidence: 87%

“…Recombination depends mainly on the fluctuations and (instantaneous) density of open ends. To compare directly with results of previous simulations of this model [11,12], we choose R 0 = 1.5 and k * = 30. All systems contain N = 8400 particles, and simulations are performed at constant temperature T * = 1 and particle density n * = 0.84, using a conservative time step of ⌬t * = 0.003.…”

Section: Methodsmentioning

confidence: 99%

“…Much stronger shear thinning is observed now, with a slope close to −1 (dashed line) for the highest concentration = 1, in apparent agreement with experimental observations. Note that the viscosity results for the FENE-C model (excluding ring formation) presented by Carl et al [12] were calculated in a similar way, i.e., disregarding solvent contributions, although the authors did not explicitly state this. As we have seen, when solvent contributions are included, the shear thinning effects become much less dramatic.…”

Section: Rheologymentioning

confidence: 99%

“…Conversely, chains can break if any of the bonds are stretched because of thermal fluctuations or tension. The FENE-C model was studied extensively by Kröger and others [11][12][13][14]. Usually, in these studies ring closure was explicitly disallowed.…”

Section: Introductionmentioning

confidence: 99%

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Influence of shear flow on the formation of rings in wormlike micelles: A nonequilibrium molecular dynamics study

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Boek

2004

Phys. Rev. E

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We study the influence of shear flow on the formation of rings in a generic reversible polymer (FENE-C) model, representative for wormlike micelles. Under equilibrium conditions, rings are dominating in dilute solutions, while linear chains are dominating in strongly overlapping and concentrated solutions. We find that shear flow induces a net shift of micellar mass from linear chains to rings. At the same time, the average aggregation size of linear chains is decreasing, while the average aggregation size of rings is increasing. We hypothesize that the increased abundance and size of rings are caused by a decreased entropy gain associated with ring opening under shear flow. Linear chains and rings are elongated in the flow direction and contracted in the gradient direction. This leaves an essentially two-dimensional free volume, which two newly created chain ends can explore after being disconnected. We study the ratio of ring and linear chain distribution functions to substantiate this hypothesis. Finally, we study the rheology and discuss how the observed increase of ring abundance can provide a positive feedback between strain and ring connectivity. Such a positive feedback can contribute to shear thickening behavior, observed in micellar solutions near the overlap concentration.

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Section: A Distribution and Average Sizesupporting

confidence: 89%

Section: A Distribution and Average Sizementioning

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Section: Rheologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of shear flow on the formation of rings in wormlike micelles: A nonequilibrium molecular dynamics study

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Boek

2004

Phys. Rev. E

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Fibers and wires in organogels from low‐mass compounds: Typical structural and rheological properties

Térech

1998

Ber Bunsenges Phys Chem

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An overview is given of the special class of thermoreversible organogels and jellies formed with low‐mass compounds. Two distinct rheological behaviors can characterize these binary systems: (1) viscoelastic liquids which develop an elasticity over short times, (2) viscoelastic solids which are constituted on long‐lived 3‐d networks at a temperature T in the gel domain of the phase diagram. Entangled, breakable giant micelles (molecular wires) are opposed to fibers interconnected through crystalline‐like microdomains. Certain thermal and rheological properties are presented as well as the detailed structural context at different scales of the fibrillar networks. A brief review of the different chemical classes of organogelators illustrates the growing development in the field. The class of viscoelastic liquids (jellies) is illustrated with the special category of monomolecular organometallic wires.

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Micro/mesoscopic approaches to the ring formation in linear wormlike micellar systems

Kröger

1998

Macromolecular Symposia

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We hereby present i) a microscopic model for the self‐assembly of linear wormlike micelles for which scission/recombination processes and loop formation are allowed, and ii) a mesoscopic analytic description of such systems. Both approaches predict the extent of loop formation as function of the micellar concentration, the end‐cap energy and the flexibility of micelles. As a matter of fact, even if loop formation is unfavorable under many conditions, e.g., for stiff micelles and low end cap energies, they have to be treated correctly in any statistical approach to their behavior, since their presence can significantly affect the relaxation time spectrum, the rheological behavior and correlation function of various types.

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On the Shape and Rheology of Linear Micelles in Dilute Solutions

Cited by 22 publications

References 2 publications

Influence of shear flow on the formation of rings in wormlike micelles: A nonequilibrium molecular dynamics study

Influence of shear flow on the formation of rings in wormlike micelles: A nonequilibrium molecular dynamics study

Fibers and wires in organogels from low‐mass compounds: Typical structural and rheological properties

Micro/mesoscopic approaches to the ring formation in linear wormlike micellar systems

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