Renormalization of Helfrich's Interactions between Fluid Membranes in a Lyotropic Lamellar Phase by Addition of Amphiphilic Copolymers

Castro-Roman, Francisco; Porte, G.; Ligoure, Christian

doi:10.1103/physrevlett.82.109

Cited by 45 publications

(74 citation statements)

References 20 publications

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“…In this work we propose a model based on a non-quadratic elastic energy, which shows that a pure lamellar phase, or one of space-filling deformed monodisperse onions, is unstable with respect to a polydisperse space-filling packing (we study an Apollonian packing [16]). We compare these predictions to experiments on copolymer-doped lamellar phases, originally introduced by Ligoure et al [17].…”

Section: Edp Sciencesmentioning

confidence: 91%

“…The lamellar structure is preserved upon adding copolymer, with a continuous hardening into a "lamellar gel". The location of this gel in the (α,φ) phase diagram was studied by Ligoure et al [17]. They observed gel-like behavior over a range of critical copolymer/surfactant weight ratios that depends on the membrane fraction.…”

Section: Edp Sciencesmentioning

confidence: 99%

“…-As shown theoretically in [26], adsorption of amphiphilic copolymers to surfactant bilayers is expected to decreaseκ, which eventually becomes negative. We therefore prepare lamellar phases decorated with copolymers [17]. Bilayers of thickness δ 0 =2.8 nm comprising cetylpyridinium chloride (CpCl) and octanol (Oct) (CpCl/Oct = 0.95 w/w) are diluted in brine ([NaCl] = 0.2 M) and decorated with Symperonics F68 (Serva) ((EO) 76 − (PO) 29 − (EO) 76 , where EO is ethylene oxide and PO is propylene oxide) as amphiphilic copolymer.…”

Section: Edp Sciencesmentioning

confidence: 99%

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Equilibrium onions?

Ramos¹,

Roux²,

Olmsted³

et al. 2004

Europhys. Lett.

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PACS. 82.70.Uv -Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems (hydrophilic and hydrophobic interactions). PACS. 68.18.Jk -Surface and interfaces; thin films and low-dimensional systems (structures and nonelectric properties): Phase transitions. PACS. 61.30.St -Lyotropic phases.Abstract. -We demonstrate the possibility of a stable equilibrium multi-lamellar ("onion") phase in pure lamellar systems (no excess solvent) due to a sufficiently negative Gaussian curvature modulus. The onion phase is stabilized by non-linear elastic moduli coupled to a polydisperse size distribution (Apollonian packing) to allow space-filling without appreciable elastic distortion. This model is compared to experiments on copolymer-decorated lamellar surfactant systems, with reasonable qualitative agreement.Introduction. -The existence of vesicles at thermal equilibrium is a long-standing, and still controversial, problem [1]. Unilamellar and multi-lamellar vesicles (MLVs) were first induced in lyotropic lamellar phases with excess water by adding energy (e.g., shear flow, ultrasound, electric field) [2]. In a very elegant work, using membranes generated by a chemical reaction, Hoffman and co-workers demonstrated that any of lamellae, unilamellar vesicles, or MLVs can be prepared in the same system, depending on the mechanical path chosen [3]. However, in some special cases [4,5] equilibrium unilamellar vesicles have been demonstrated. These systems are all in the dilute regime (large excess of water). Some experiments have suggested that MLVs (or onions) can be stabilized in the semi-dilute regime (excess water) [5]. Theories to explain the stability of dilute unilamellar vesicles either describe a competition between the entropy of mixing and the curvature energy of the vesicles [5][6][7] or a symmetrybreaking instability leading to a spontaneous curvature [8]. Onions are also predicted to be stabilized in the dilute and semi-dilute regimes due to an unstable curvature energy; in these cases, a transition towards unilamellar vesicles is avoided by imposing either a core energy [9] or a cutoff in the entropy of the Helfrich interactions [10]. Indeed, Simons and Cates [10] have discussed the stability of unilamellar vesicles and the transition to onions as the concentration increases even when the curvature energy is unfavorable, due to entropic reasons.

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Section: Edp Sciencesmentioning

confidence: 91%

Section: Edp Sciencesmentioning

confidence: 99%

Section: Edp Sciencesmentioning

confidence: 99%

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Equilibrium onions?

Ramos¹,

Roux²,

Olmsted³

et al. 2004

Europhys. Lett.

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show abstract

“…Adhesion of membranes on a substrate plays a role in biological phenomena such as endocytosis and exocytosis [2], it is also of relevance in biotechnological processes, such as drug delivery by liposomes [36]. A second important case of constraint membranes corresponds to lamellar L α phases, where the membranes are confined by interactions with their neighbors in the lamella stack [4,37].…”

Section: Polymers Anchored On a Constrained Membranementioning

confidence: 99%

Local entropic effects of polymers grafted to soft interfaces

Bickel

Jeppesen

Marques

2001

The European Physical Journal E

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In this paper, we study the equilibrium properties of polymer chains end-tethered to a fluid membrane. The loss of conformational entropy of the polymer results in an inhomogeneous pressure field that we calculate for gaussian chains. We estimate the effects of excluded volume through a relation between pressure and concentration. Under the polymer pressure, a soft surface will deform. We calculate the deformation profile for a fluid membrane and show that close to the grafting point, this profile assumes a cone-like shape, independently of the boundary conditions. Interactions between different polymers are also mediated by the membrane deformation. This pair-additive potential is attractive for chains grafted on the same side of the membrane and repulsive otherwise.

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“…5) In such block † Tel: +81-258-47-9302, Email: sfujii@mst.nagaokaut.ac.jp copolymer-grafted systems, it has been considered that the hydrophobic part in the triblock copolymer is embedded in the hydrophobic layer of the membrane, and hydrophilic part decorates the membrane. 7,8) In the hydrophilic polymer decorated systems, by controlling the concentration X P and the degree of polymerization N EO of the hydrophilic part in the grafted triblock copolymer, we found that the critical shear stress is monotonically increased with X P and N EO , and the onion phase formation is mechanically suppressed by grafting polymers. We have presented that the critical shear stress of the onion formation σ C can be well scaled by taking account of effective increment in the bending modulus of the polymergrafted bilayer membrane ∆κ ~ X P N EO still not clear how the hydrophobic PO part affects the onion formation behavior through the increase in the bending rigidity.…”

Section: Introductionmentioning

confidence: 97%

Shear-induced Onion Formation of Triblock Copolymer-embedded Surfactant Lamellar Phase

Fujii

Mitsumasu

Isono

2013

J. Soc. Rheol., Jpn

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We study the shear-induced lamellar/onion transformation of the amphiphilic triblock copolymer-embedded surfactant lamellar phase. Increase in the mole fraction of polymer X P and the degrees of polymerization of hydrophobic PO chain N PO allows to increase the critical shear stress. The critical shear stress σ C can be scaled by the effective increment of the bending modulus, which is originally predicted for the hydrophilic polymer-grafted membranes, ∆κ ~ X P N 1.2 . N PO dependence of the onion size is attributed to the disturbed compression modulus of the membrane via the embedded hydrophobic chain. All of these influences on the onion formation will be attributed to the configuration entropy of the embedded hydrophobic polymers in the bilayer.

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Renormalization of Helfrich's Interactions between Fluid Membranes in a Lyotropic Lamellar Phase by Addition of Amphiphilic Copolymers

Cited by 45 publications

References 20 publications

Equilibrium onions?

Equilibrium onions?

Local entropic effects of polymers grafted to soft interfaces

Shear-induced Onion Formation of Triblock Copolymer-embedded Surfactant Lamellar Phase

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