Confined diffusion of hydrophilic probes inserted in lyotropic lamellar phases

• Published in: The European physical journal. A, Hadrons and nuclei Vol. 26; no. 3; pp. 225 - 234
• Main Authors: Moreau, P., van Effenterre, D., Navailles, L., Nallet, F., Roux, D.
• Format: Journal Article
• Language: English
• Published: Bologna Società Italiana di Fisica 01.07.2008; Springer; EDP Sciences ; Springer [1998-....]
• Subjects: Biological and Medical Physics; Biophysics; Chemical Sciences; Chemistry; Colloidal state and disperse state; Complex Fluids and Microfluidics; Complex Systems; Diffusion; Dioctyl Sulfosuccinic Acid - chemistry; Exact sciences and technology; Fluorescence; General and physical chemistry; Hexanols - chemistry; Lipid Bilayers - chemistry; Membrane Fluidity; Membranes; Microscopy, Confocal; Models, Molecular; Nanotechnology; or physical chemistry; Phase Transition; Physics; Physics and Astronomy; Polymer Sciences; Regular Article; Serum Albumin, Bovine - chemistry; Sodium Chloride - chemistry; Soft and Granular Matter; Solutions - chemistry; Surface Properties; Surface-Active Agents - chemistry; Surfaces and Interfaces; Theoretical and; Thin Films; Water - chemistry; 82.70.-y Disperse systems; complex fluids; 87.64.mk Confocal; 82.56.Lz Diffusion; 87.16.dj Dynamics and fluctuations; Water; Confinement; Non ionic surfactant; Alcohol; Sodium chloride; Probe; Hydrophily; Ethylene oxide polymer; Anionic surfactant; Hexyl alcohol; Lamellar structure; Alkanol; Membrane; Aerosol OT; Diffusion; Lyotropic state; Disperse systems; Confocal; complex fluids; Dynamics and fluctuations
• ISSN: 1292-8941; 1434-6001; 1292-895X; 1434-601X
• DOI: 10.1140/epje/i2007-10318-9

. The dynamic behaviour of three hydrophilic probes (two dyes and one fluorescently-labelled protein) inserted in the water layers of lyotropic lamellar phases has been studied by confocal fluorescence recovery experiments. Two different, ionic (AOT/NaCl/ H 2 O and non-ionic ( C 12 E 5 /hexanol/ H 2 O host systems were studied. The confinement effect has been carefully monitored using the swelling properties of the lamellar phases. In all cases, we measure the evolution of the probe diffusion coefficient in the layer plane D ⊥ versus the separation between the membranes d w . Depending on the composition of the lamellar phase, this distance can be continuously adjusted from 500Å to about 20Å. For all systems, we observe a first regime, called dilute regime, where the diffusion coefficient decreases almost linearly with 1/ d w . In this regime, the Faxén theory for the friction coefficient of a spherical particle symmetrically dragged between two rigid walls can largely explain our results. More unexpectedly, when the membranes are non-ionic, and also quite flexible ( C 12 E 5 /hexanol in water), we observe the existence of a second, concentrated (or confined) regime, where the diffusion coefficient is nearly constant and different from zero for membrane separations smaller than the particle size. This new regime can be heuristically explained by simple arguments taking into account the membrane fluidity.