Ferrosmectics: A new magnetic and mesomorphic phase

Fabre, Pascale; Casagrande, C.; Veyssié, M.; Cabuil, Valérie; Massart, R.

doi:10.1103/physrevlett.64.539

Cited by 139 publications

(72 citation statements)

References 9 publications

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“…The wealth of information collected over the past two decades on L a and L 3 phases designates them as convenient tools to investigate interactions between membranes and other components often present in synthetic or naturally occurring colloidal suspensions. L a phases have for instance been used to host ferromagnetic colloidal particles [7] and different types of polymers [8][9][10][11], both in the intermembrane solvent subphase [12,13] and inside the bilayer itself [14]. In this Letter we investigate by small angle x-ray and neutron scattering the structure of L a and L 3 phases with embedded polysoaps, a particular class of macromolecular surfactants.…”

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confidence: 98%

Confinement of Polysoaps in Membrane Lyotropic Phases

et al. 1998

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We study the confinement of polysoaps in lyotropic smectic (L a ) and sponge (L 3 ) solutions of the nonionic surfactant pentaethylene glycol dodecyl ether (C 12 EO 5 ). The polysoap is a hydrophobically modified polymer with n-tetradecyl sidegroups randomly grafted to a polyacrylate backbone. Without the hydrophobic side chains the backbone polymer cannot be embedded into the intermembrane space, but confinement is achieved for a polysoap with as low as 1% of grafted groups. We measure by small angle x-ray and neutron scattering an increase of the bending rigidity of the lamellar membranes as a function of polysoap concentration. [S0031-9007(98)05642-7] PACS numbers: 83.70.Hq, 64.75. + g, 82.65.DpFluid membranes are two-dimensional structures, selfassembled from surfactant solutions [1]. In the biological realm, phospholipid bilayers constitute the walls of liposomes and cells, hosting proteins responsible for functions as diverse as anchoring the cytoskeleton, providing coating protection against the body immune response or opening ionic channels for osmotic compensation [2]. Membranes are also present in many surfactant based industrial formulations. For instance, the processing and delivery of detergents or conditioning agents often require at some stage the use of concentrated surfactant solutions where lyotropic liquid crystals are formed [3]. The simplest liquid crystalline phase of membranes is the lamellar phase L a , a smectic A lyotropic liquid crystal [4]. It consists of one-dimensional stacks of surfactant bilayers, separated by a solvent. Its one-dimensional symmetry allows for a relatively straightforward experimental determination of many properties pertaining not only to the ordered phase as a collective body of interacting membranes but also to each individual bilayer with its intrinsic constitutive elasticity [5]. Also of interest for our study is the sponge phase L 3 , a bicontinuous isotropic phase of multiconnected membranes [6]. The wealth of information collected over the past two decades on L a and L 3 phases designates them as convenient tools to investigate interactions between membranes and other components often present in synthetic or naturally occurring colloidal suspensions. L a phases have for instance been used to host ferromagnetic colloidal particles [7] and different types of polymers [8][9][10][11], both in the intermembrane solvent subphase [12,13] and inside the bilayer itself [14]. In this Letter we investigate by small angle x-ray and neutron scattering the structure of L a and L 3 phases with embedded polysoaps, a particular class of macromolecular surfactants. By studying a system of very flexible membranes, we were able to quantitatively determine, for the first time, the variation of the elastic constant of the membranes as a function of the concentration of added polymer.The L a and L 3 phases under investigation are composed of membranes of the nonionic surfactant C 12 EO 5 (from Nikko, Japan) and hexanol in a NaCl brine solution at 0.1M. Pure water͞C 12 EO 5 mixtur...

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confidence: 98%

Confinement of Polysoaps in Membrane Lyotropic Phases

et al. 1998

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“…The evolution of the ferrosmectic LB during the orientation process by a rotating field on the one hand, and when a field is applied parallel to the layer plane on the other hand, is well understood in the framework of equations (1,2).…”

Section: Discussionmentioning

confidence: 99%

“…The former is built from a lyotropic lamellar phase in which the oil solvent has been replaced by a ferrofluid, which is a suspension of maghemite (γFe 2 O 3 ) nanoparticles in cyclohexane [1]. The latter is constituted of a similarly substituted swollen hexagonal phase.…”

Section: Introductionmentioning

confidence: 99%

Magneto-optical study of the orientation confinement of particles in ferrolyotropic systems

et al. 2000

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Ferrosmectics and ferrohexagonals are magnetic liquid crystals which consist of a lamellar and a hexagonal phase in which magnetic nanoparticles are incorporated. The magnetic field variation and the relaxation of the linear optical birefringence of ferrosmectics and ferrohexagonals and its time relaxation are measured in different geometries and compared with that of a ferrofluid sample. We interpret our data by the existence of a mean orientation of the magnetic particles in the lyotropic structure, which appears to be non-random in zero field. We conclude that the magnetic moments of the particles are preferentially aligned in the plane of the ferrosmectic layers and along the axis of the ferrohexagonal cylinders, respectively. To account for this preferred alignment, we propose that some of the particles in the ferrosmectic are adsorbed on the surfactant layers with their moment aligned in the lamellar plane, while the orientation of the moments in the ferrohexagonal is restricted to a cone around the cylinder axis.PACS. 75.50.Mm Magnetic liquids -78.20.Ls Magnetooptical effects -61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

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“…Particles of γ-Fe 2 O 3 (diameter of 8 nm) coated with organophosphorated surfactants and dispersed in cyclohexane, were incorporated in a lyotropic lamellar phase [75][76][77]. Stable ferrolamellar phases, without the formation of aggregates and phase separation, were observed under some particular conditions, at φ = 1.5%.…”

Section: Doping Of Lyotropic Liquid Crystals With Magnetic Particlesmentioning

confidence: 99%

Ferrofluids: properties and applications

Scherer¹,

2005

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Magnetic fluids may be classified as ferrofluids (FF), which are colloidal suspensions of very fine (∼ 10 nm) magnetic particles, and magnetorheological fluids, which are suspensions of larger, usually non-stable, magnetic particles. We review the general classification and the main properties of FF, some theoretical models and a few applications. We consider the stability of a FF in terms of various forces and torques on the magnetic particles. We discuss thermodiffusion, which is an important phenomenon in FF, and which gives rise to the Soret effect. We also consider the rotational dynamics of the magnetic moments of the particles. A large portion of this review is dedicated to applications of FF, including a few of the many technological applications. Among the uses of a FF in the study of materials, we have selected the doping of liquid crystals. Among the very promising uses in Medicine, we discuss drug targeting, hyperthermia, cell separation, and contrast in magnetic resonance imaging. We also make some comments on directions for future research on the properties of ferrofluids.

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Ferrosmectics: A new magnetic and mesomorphic phase

Cited by 139 publications

References 9 publications

Confinement of Polysoaps in Membrane Lyotropic Phases

Confinement of Polysoaps in Membrane Lyotropic Phases

Magneto-optical study of the orientation confinement of particles in ferrolyotropic systems

Ferrofluids: properties and applications

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