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The European Physical Journal E

, Volume 18, Issue 2, pp 219–230 | Cite as

Role of dislocation loops on the elastic constants of lyotropic lamellar phases

  • E. FreyssingeasEmail author
  • A. Martin
  • D. Roux
Original Article

Abstract.

We study the role of dislocation loops defects on the elasticity of lamellar phases by investigating the variation of the lamellar elastic constants, ¯ and K, induced by the proliferation of these defects. We focus our interest on one particular lamellar phase made up of a mixture of C12E5 and DMPC in water, which is already well-characterised. This lamellar phase undergoes a second-order (or weakly first-order) lamellar-to-nematic phase transition at about 19°C and dislocation loops are seen to proliferate within the lamellar structure when temperature is decreased below 30°C. The values of both elastic constants of this given lamellar phase are measured as a function of temperature, approaching the lamellar-to-nematic transition, with the help of Quasi-Elastic Light Scattering (QELS) on oriented lamellar phases. Very surprisingly we observe a strong and rapid increase in both ¯ and K as the lamellar-to-nematic transition temperature is approached. These increases are seen to start as soon as dislocation loops can be observed in the lamellar phase. We interpret our results as being the consequence of the appearance and proliferation of dislocation loops within the lamellar structure. According to a simple model we developped we show that ¯ and K are proportional to the density of dislocation loops in the lamellar phase.

PACS.

61.30.St Lyotropic phases 61.30.Jf Defects in liquid crystals 82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions) 87.16.Dg Membranes, bilayers, and vesicles 

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Copyright information

© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2005

Authors and Affiliations

  1. 1.Laboratoire de PhysiqueUMR CNRS 5672, Ecole Normale Supérieure de LyonLyonFrance
  2. 2.Centre de recherche Paul PascalUPR CNRS 8641PessacFrance

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