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Subgel transition in diluted vesicular DODAB dispersions

Saveyn, Pieter LU ; Van der Meeren, Paul; Zackrisson Oskolkova, Malin LU ; Narayanan, Theyencheri and Olsson, Ulf LU (2009) In Soft Matter 5(8). p.1735-1742
Abstract
We have characterized the lipid chain freezing in dilute aqueous vesicle dispersions of the cationic lipid dioctadecyldimethylammonium bromide (DODAB) using wide and small angle X-ray scattering, solid state NMR, DSC, turbidity and density measurements. The lipids freeze in two steps. Above 40 degrees C the chains are fluid and the lipids are in a so-called liquid-crystalline state. When cooling below 40 degrees C, the lipids form a gel phase where the chains stretch, the molecules are more densely packed and most molecular degrees of freedom are frozen, or at least dramatically slowed down. In the gel phase, the chain packing is still disordered, while the chain mobility is significantly reduced. From NMR data we further conclude that... (More)
We have characterized the lipid chain freezing in dilute aqueous vesicle dispersions of the cationic lipid dioctadecyldimethylammonium bromide (DODAB) using wide and small angle X-ray scattering, solid state NMR, DSC, turbidity and density measurements. The lipids freeze in two steps. Above 40 degrees C the chains are fluid and the lipids are in a so-called liquid-crystalline state. When cooling below 40 degrees C, the lipids form a gel phase where the chains stretch, the molecules are more densely packed and most molecular degrees of freedom are frozen, or at least dramatically slowed down. In the gel phase, the chain packing is still disordered, while the chain mobility is significantly reduced. From NMR data we further conclude that also the molecular rotational diffusion around the molecular long axis is quenched. Slow chain reorientation may occur, but then as individual reorientations of the separate chains. When cooling further below 36 degrees C, crystalline ordering of the chains is obtained, resulting in a further increased packing density. We refer to this state as the subgel phase. The transitions are reversible. However, the formation of the ordered subgel is very slow for temperatures near the melting point. In fact, the gel phase can be supercooled by almost 20 degrees C for considerable time. From analyzing this transition in terms of classical nucleation we obtain an estimate of the intra-bilayer interfacial tension between the gel phase and the growing subgel domains of 2 mN m(-1). (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soft Matter
volume
5
issue
8
pages
1735 - 1742
publisher
Royal Society of Chemistry
external identifiers
  • wos:000265017200025
  • scopus:64549088472
ISSN
1744-6848
DOI
10.1039/b821387a
language
English
LU publication?
yes
id
aadcd0bb-9e2f-4a6a-88af-115706ef29a1 (old id 1400482)
date added to LUP
2009-06-12 11:20:32
date last changed
2017-10-01 04:28:05
@article{aadcd0bb-9e2f-4a6a-88af-115706ef29a1,
  abstract     = {We have characterized the lipid chain freezing in dilute aqueous vesicle dispersions of the cationic lipid dioctadecyldimethylammonium bromide (DODAB) using wide and small angle X-ray scattering, solid state NMR, DSC, turbidity and density measurements. The lipids freeze in two steps. Above 40 degrees C the chains are fluid and the lipids are in a so-called liquid-crystalline state. When cooling below 40 degrees C, the lipids form a gel phase where the chains stretch, the molecules are more densely packed and most molecular degrees of freedom are frozen, or at least dramatically slowed down. In the gel phase, the chain packing is still disordered, while the chain mobility is significantly reduced. From NMR data we further conclude that also the molecular rotational diffusion around the molecular long axis is quenched. Slow chain reorientation may occur, but then as individual reorientations of the separate chains. When cooling further below 36 degrees C, crystalline ordering of the chains is obtained, resulting in a further increased packing density. We refer to this state as the subgel phase. The transitions are reversible. However, the formation of the ordered subgel is very slow for temperatures near the melting point. In fact, the gel phase can be supercooled by almost 20 degrees C for considerable time. From analyzing this transition in terms of classical nucleation we obtain an estimate of the intra-bilayer interfacial tension between the gel phase and the growing subgel domains of 2 mN m(-1).},
  author       = {Saveyn, Pieter and Van der Meeren, Paul and Zackrisson Oskolkova, Malin and Narayanan, Theyencheri and Olsson, Ulf},
  issn         = {1744-6848},
  language     = {eng},
  number       = {8},
  pages        = {1735--1742},
  publisher    = {Royal Society of Chemistry},
  series       = {Soft Matter},
  title        = {Subgel transition in diluted vesicular DODAB dispersions},
  url          = {http://dx.doi.org/10.1039/b821387a},
  volume       = {5},
  year         = {2009},
}