On the nature of the intramicellar and intermicellar forces governing the liquid crystalline phase behavior of aqueous solutions of disklike micelles

Boden, N.; Harding, Rebecca; Gelbart, William M.; Ohara, Pamela C.; Jolley, K. W.; Heerdegen, Aidan; Parbhu, A

doi:10.1063/1.470553

Cited by 27 publications

(29 citation statements)

References 32 publications

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“…The volume for the endgroup CF 3 is 84.5 Å 3 , as compared to 27 Å 3 for CH 3 , according to Tanford . The contribution per CX 2 to the length of the fully extended (all-trans) tail was given as 1.30 Å in the fluorocarbons and 1.26 Å in the hydrocarbons . The fluorocarbon tail cross-section area would then be 31.5 Å 2 , compared to 21.4 Å 2 for the hydrocarbon; similar values have been deduced by others. , The surfactant parameter can then be calculated, for fluorocarbon: a tail / a 0 = 31.3 Å 2 / a 0 , and for the hydrocarbon analogue 21.3 Å 2 / a 0 .…”

Section: Discussionmentioning

confidence: 99%

Aggregation Behavior of Cationic Fluorosurfactants in Water and Salt Solutions. A CryoTEM Survey

et al. 1999

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The aggregation behavior of the cationic fluorocarbon surfactants 1,1,2,2-tetrahydroperfluoroalkylpyridinium chloride and 2-hydroxy-1,1,2,3,3-pentahydroperfluoroalkyldiethylammonium chloride in aqueous solution have been studied using cryo-transmission electron microscopy as the main technique. The effects on aggregate structure of factors such as surfactant and salt concentration, counterion type, and alkyl chain length were investigated. Similar to hydrocarbon surfactants the fluorocarbon surfactants self-assemble into various aggregates such as micelles, threadlike micelles, vesicles, and other lamellar aggregates. A distinctive property of the fluorocarbon surfactants is their tendency to form structures with little curvature, such as cylindrical micelles and bilayer structures. Even a very small reduction of the repulsion between the headgroups is sufficient to accomplish a sphere to rod transition, so that a solution of globular micelles in water is turned into a highly viscous, sometimes viscoelastic solution on the addition of low concentrations of a simple salt. The differences between the fluorocarbon and hydrocarbon surfactants are discussed.

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Section: Discussionmentioning

confidence: 99%

Aggregation Behavior of Cationic Fluorosurfactants in Water and Salt Solutions. A CryoTEM Survey

et al. 1999

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“…Thus the L D phase exhibits the positional ordering of disc-like micelles into planes arranged periodically along the nematic director, n. However, some experiments suggest that the lamellar phase consists of continuous bilayers. In many systems, such as lyotropic liquid crystals [1][2][3][4][5][6][7] and block copolymers, [8][9][10][11] transition is observed from a uniform isotropic to a lamellar phase upon lowering the temperature. Experimental results [1][2][3][4][5][6][7] and theoretical predictions [12][13][14] support the evidence of the presence of a transition from the isotropic micellar (I) to a lamellar phase transition in a lyotropic liquid crystal (LLC) system.…”

Section: Introductionmentioning

confidence: 99%

“…In many systems, such as lyotropic liquid crystals [1][2][3][4][5][6][7] and block copolymers, [8][9][10][11] transition is observed from a uniform isotropic to a lamellar phase upon lowering the temperature. Experimental results [1][2][3][4][5][6][7] and theoretical predictions [12][13][14] support the evidence of the presence of a transition from the isotropic micellar (I) to a lamellar phase transition in a lyotropic liquid crystal (LLC) system. Roux and Knobler 3 studied the dynamics of the phase separation between a dilute lyotropic lamellar phase (SmA) and an isotropic phase in a quaternary (water, sodium dodecyl sulfate, pentanol, dodecane) system.…”

Section: Introductionmentioning

confidence: 99%

“…By means of small-angle light scattering, they studied the phase separation process involving the nucleation and growth of the isotropic phase in the lamellar phase. In experimental studies, 1,2,[4][5][6][7] the binary mixtures of cesium perfluoro-octanoate (CsPFO)-water/heavy water (H 2 O/D 2 O) and APFO-D 2 O systems were found to produce the I, N D and L D phases. At a fixed concentration such a system undergoes the phase transitions with decreasing temperature from the isotropic micellar (I) phase to the L D phase (I-L D ) via a triple point.…”

Section: Introductionmentioning

confidence: 99%

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Isotropic micellar to lamellar phase transition in lyotropic liquid crystals

Mukherjee

2013

RSC Adv.

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A phenomenological theory is presented to describe the isotropic micellar to lamellar (I-L D ) phase transition in lyotropic liquid crystals. The model free energy is written in terms of the coupled order parameters including the micellar concentration. The conditions for the I-L D phase transition and the stability conditions of the lamellar phase are calculated. On the basis of this model, it is argued that the I-L D phase transition is always first order. The theoretical predictions are found to be in good qualitative agreement with available experimental results. II. Model A. Order parameterWe start by describing the order parameters involved in the I-L D transition for LLC. The L D phase has the same symmetries

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“…[21][22][23] Moreover, a number of different theoretical approaches dealing with ͑biaxial͒ rodlike or disklike micelles have been published in recent years. [24][25][26][27][28][29] However, triaxial tablet-shaped micelles that are able to grow with respect to both width and length have never been treated before the present work. In order to determine the size and shape of micelles we have, in the theory to be presented below, combined the curvature free energy approach with a rigorous thermodynamic treatment 1,2,30 of the formation of a dispersed solution of surfactant aggregates.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of anisotropic surfactant micelles. I. The influence of curvature free energy on the micellar size and shape

Bergström

2000

The Journal of Chemical Physics

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Articles you may be interested inFree energy profiles for penetration of methane and water molecules into spherical sodium dodecyl sulfate micelles obtained using the thermodynamic integration method combined with molecular dynamics calculations A molecular dynamics study of free energy of micelle formation for sodium dodecyl sulfate in water and its size distribution Thermodynamics of anisotropic surfactant micelles. II. A molecular interpretation of the micellar curvature free energy A novel theory for the structural behavior of surfactant micelles is expounded. The micelles are considered to be generally shaped as triaxial tablets with distinct thickness width and length, respectively, and may become spherical, spherocylindrical or disk-shaped in the special cases where two or more of the dimensions are equal. It is demonstrated that the average width and length of a tablet-shaped micelle with a fixed thickness is mainly determined by two constants, k 1 and k 2 , related to the first and second order correction in curvature of the micellar end caps. The size of the micelles is found to be mainly determined by k 1 , whereas k 2 influences the shape, i.e., the length-to-width ratio, of the micelles so that the micellar size increases with increasing k 1 and the length-to-width ratio decreases with increasing k 2 . Hence, large positive values of k 2 promote the formation of tablets rather than very long spherocylinders. An additional parameter related to the curvature of the straight cylindrical rims may influence the structure of the tablet-shaped micelles insofar k 2 is close to or below zero.

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On the nature of the intramicellar and intermicellar forces governing the liquid crystalline phase behavior of aqueous solutions of disklike micelles

Cited by 27 publications

References 32 publications

Aggregation Behavior of Cationic Fluorosurfactants in Water and Salt Solutions. A CryoTEM Survey

Aggregation Behavior of Cationic Fluorosurfactants in Water and Salt Solutions. A CryoTEM Survey

Isotropic micellar to lamellar phase transition in lyotropic liquid crystals

Thermodynamics of anisotropic surfactant micelles. I. The influence of curvature free energy on the micellar size and shape

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