From rodlike micelles to lyotropic liquid crystals

Angel, Miguel; Hoffmann, H.; Löbl, M.; Reizlein, K.; Thurn, H.; Wunderlich, I.

doi:10.1007/bfb0114960

Cited by 13 publications

(17 citation statements)

References 21 publications

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“…It is for instance straightforward to show by electric or flow birefringence measurements that the micelles must be nonisometric [34]. Detailed analysis of the amplitude and time constants, particularly when combined with data from lightscattering, allows for the differentation between rodlike and disclike micelles [35]. On the basis of dynamic and static light scattering data it is usually also possible to determine which 'one of the possible forms is the existing one.…”

Section: Experimental Evidence Jor Rodlike Micellesmentioning

confidence: 99%

Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour

1986

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The first part of the work presents an overview of the physical chemistry of surfactants which in aqueous solutions reduce the frictional loss in turbulent pipe flow. It is shown that these surfactants form rodlike micelles above a characteristic concentraion c t. The experimental evidence for rodlike micelles are reviewed and the prerequisites that the surfactant system must fulfill in order to form rodlike micelles are given. It is demonstrated by electrical conductivity measurements that the critical concentration for the formation of spherical micelles shows little temperature dependence, whereas ct increases very rapidly with temperature. The length of the rodlike micelles, as determined by electric birefringence, decreases with rising temperature and increases with rising surfactant concentration. The dynamic processes in these micellar systems at rest and the influence of additives such as electrolytes and short chain alcohols are discussed.In the second part, the rheological behaviour of these surfactant solutions under laminar and turbulent flow conditions are investigated. Viscosity measurements in laminar pipe and Couette flow show the build-up of a shear induced viscoelastic state, SIS, from normal Newtonian fluid flow. A complete alignment of the rodlike micelles in the flow direction in the SIS was verified by flow birefringence. In turbulent pipe flow, drag reduction occurs in these surfactant systems as soon as rodlike micelles are present in the solution. The extent and type of drag reduction, i.e. the shape of the friction factor versus Reynolds number curve, depends directly on the size, number and surface charge of the rodlike micelles. The friction factor curve of each surfactant investigated changes in the same characteristic way as a function of temperature. For each surfactant, independent of concentration, an upper absolute temperature limit, TL, for drag reduction exists which is caused by the micellar dynamics. T L is influenced by the hydrophobic chain length and the counter-ion of the surfactant system. A first attempt is made to explain the drag reduction of surfactants by combining the results of these rheological measurements with the physico-chemical properties of the micellar systems.

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Section: Experimental Evidence Jor Rodlike Micellesmentioning

confidence: 99%

Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour

1986

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“…Moreover, Rao et al [16] emphasized that the unique orientation of the salicylate ion on the micellar surface is the crucial factor for inducing viscoelasticity, and they proposed two kinds of linking mechanisms between micelles. Although Rao et al imagined the formation of a chain of micellar beads or of spherical micelles, some investigators [10,11,18] confirmed the formation of rodlike micelles in aqueous solutions of C14TASal and C16TASal. Their lengths were 20-60 nm in water at 20 ~ [101 and 200-300 nm in 10 mM NaC1 at 25 ~ [11].…”

Section: Discussionmentioning

confidence: 93%

The spinnability of viscoelastic solutions of tetradecyl- and hexadecyl-trimethylammonium salicylates

Imae

Hashimoto

Ikeda

1990

Colloid & Polymer Sci

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Abstract:The spinnability was measured for aqueous viscoelastic solutions of tetradecyland hexadecyltrimethylammonium salicylates (C14TASal, C16TASal) in the absence and presence of sodium salicylate (NaSal) and sodium bromide (NaBr). The spinnability is classified into two types, D and C. While the intrinsic drawing length in type D is proportional to the drawing velocity, the drawing intrinsic length in type C decreases with the drawing velocity or is independent of it. The spinnability changes from type D to C, as the drawing velocity and the surfactant concentration increase, and the temperature lowers. The effect of salt is different between NaSal and NaBr. It can be assumed that a pseudo-network structure composed of rod-like micelles is formed in viscoelastic and spinnable surfactant solutions. Then, the spinnability depends on the balance between the elasticity and the viscosity in which the structure results.

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“…Recently the border between micellar solutions and lyotropic liquid crystals where cylindrical and disclike micelles and nematic phases are situated [4,5,17] has been studied extensively. Their formation usually requires the addition of a third component and most of the nematic phases are rather narrow in their concentration range.…”

Section: The Self-aggregation Of Amphiphiles In Watermentioning

confidence: 99%

Structural variations in amphiphiles: Discoidal multivalent cations

Keller-Griffith¹,

Ringsdorf²,

Vierengel³

1986

Colloid & Polymer Sci

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Fourteen cationic multipolar amphiphiles have been synthesized with pyridinium or trimethylammonium head groups. The hydrophobic cores are planar ring systems (benzene or triphenylene) to which two, three, four, or six decylene or undecylene alkyl chains are attached by ester linkages. The hydrophilic head groups are bound to the outer ends of the alkyl chains.The aggregation of the molecules in water into micelles and lyotropic liquid crystals has been studied. Hexagonal phases are preferred to lamellar phases by these amphiphiles and in more dilute solutions some of these muhipolar amphiphiles form cylindrical micelles.

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From rodlike micelles to lyotropic liquid crystals

Cited by 13 publications

References 21 publications

Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour

Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour

The spinnability of viscoelastic solutions of tetradecyl- and hexadecyl-trimethylammonium salicylates

Structural variations in amphiphiles: Discoidal multivalent cations

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