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A comprehensive, time-resolved SANS investigation of temperature-change-induced sponge-to-lamellar and lamellar-to-sponge phase transformations in comparison with 2H -NMR results

Gotter, Martin; Sottman, Thomas; Baciu, Magdalena; Olsson, Ulf LU ; Wennerström, Håkan LU and Strey, Reinhard (2007) In European Physical Journal E. Soft Matter 24(3). p.277-295
Abstract
Time-resolved small-angle neutron scattering (TR-SANS) was employed to observe temperature-induced phase transitions from the sponge (L-3 to the lamellar ( L (alpha) phase, and vice versa, in the water-oil (n-decane)-non-ionic surfactant (C12E5 system using both bulk and film contrast. Samples of different bilayer volume fractions phi and solvent viscosities eta were investigated applying various amplitudes of temperature jump Delta T . The findings of a previous H-2-NMR study could be confirmed, where the lamellar phase formation was determined to occur through a nucleation and growth process, while it was concluded that the L-3-phase develops in a mechanistically different and more rapid manner involving uncorrelated passage formation.... (More)
Time-resolved small-angle neutron scattering (TR-SANS) was employed to observe temperature-induced phase transitions from the sponge (L-3 to the lamellar ( L (alpha) phase, and vice versa, in the water-oil (n-decane)-non-ionic surfactant (C12E5 system using both bulk and film contrast. Samples of different bilayer volume fractions phi and solvent viscosities eta were investigated applying various amplitudes of temperature jump Delta T . The findings of a previous H-2-NMR study could be confirmed, where the lamellar phase formation was determined to occur through a nucleation and growth process, while it was concluded that the L-3-phase develops in a mechanistically different and more rapid manner involving uncorrelated passage formation. Likewise, the kinetic trends of the nucleation and growth transition (decreased transition time with increase of phi and Delta T were witnessed once again. Additionally, NMR and SANS data that demonstrate a strong dependency of that process on solvent viscosity eta are presented. Contrariwise, it is made evident via both SANS and NMR results that the L-alpha-to-L-3 transition time is independent (within experimental sensitivity) of the varied parameters (phi, Delta T, eta) . Unusual scattering evolution in one experiment, originating from a highly ordered lamellar phase, intriguingly hints that a major rate determining factor is the disruption of long-range order. Furthermore, the bulk contrast investigations give insight into structure peak shifts/development during the transitions, while the film contrast experiments prove the bilayer thickness to be constant throughout the phase transitions and show that there is no evidence for a change in the short-range order of the bilayer structure. The latter was considered possible, due to the different topology of the L-3 and L-alpha phases. Lastly, an unexpected yet consistent appearance of anisotropic scattering is detected in the L-3-to-L-alpha transitions. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
KINETICS, BILAYERS, BEHAVIOR, MICROEMULSIONS, L3 PHASES, DILUTE LAMELLAR, C12E6/D2O SYSTEM, NONIONIC SURFACTANT, ANGLE NEUTRON-SCATTERING, MEMBRANE-FUSION
in
European Physical Journal E. Soft Matter
volume
24
issue
3
pages
277 - 295
publisher
Springer
external identifiers
  • wos:000251770200009
  • scopus:37449013899
ISSN
1292-8941
DOI
10.1140/epje/i2007-10238-8
language
English
LU publication?
yes
id
7e7d1ada-66a4-4deb-b654-a1e15852fcb5 (old id 1026745)
date added to LUP
2008-02-07 00:50:41
date last changed
2017-01-01 07:24:26
@article{7e7d1ada-66a4-4deb-b654-a1e15852fcb5,
  abstract     = {Time-resolved small-angle neutron scattering (TR-SANS) was employed to observe temperature-induced phase transitions from the sponge (L-3 to the lamellar ( L (alpha) phase, and vice versa, in the water-oil (n-decane)-non-ionic surfactant (C12E5 system using both bulk and film contrast. Samples of different bilayer volume fractions phi and solvent viscosities eta were investigated applying various amplitudes of temperature jump Delta T . The findings of a previous H-2-NMR study could be confirmed, where the lamellar phase formation was determined to occur through a nucleation and growth process, while it was concluded that the L-3-phase develops in a mechanistically different and more rapid manner involving uncorrelated passage formation. Likewise, the kinetic trends of the nucleation and growth transition (decreased transition time with increase of phi and Delta T were witnessed once again. Additionally, NMR and SANS data that demonstrate a strong dependency of that process on solvent viscosity eta are presented. Contrariwise, it is made evident via both SANS and NMR results that the L-alpha-to-L-3 transition time is independent (within experimental sensitivity) of the varied parameters (phi, Delta T, eta) . Unusual scattering evolution in one experiment, originating from a highly ordered lamellar phase, intriguingly hints that a major rate determining factor is the disruption of long-range order. Furthermore, the bulk contrast investigations give insight into structure peak shifts/development during the transitions, while the film contrast experiments prove the bilayer thickness to be constant throughout the phase transitions and show that there is no evidence for a change in the short-range order of the bilayer structure. The latter was considered possible, due to the different topology of the L-3 and L-alpha phases. Lastly, an unexpected yet consistent appearance of anisotropic scattering is detected in the L-3-to-L-alpha transitions.},
  author       = {Gotter, Martin and Sottman, Thomas and Baciu, Magdalena and Olsson, Ulf and Wennerström, Håkan and Strey, Reinhard},
  issn         = {1292-8941},
  keyword      = {KINETICS,BILAYERS,BEHAVIOR,MICROEMULSIONS,L3 PHASES,DILUTE LAMELLAR,C12E6/D2O SYSTEM,NONIONIC SURFACTANT,ANGLE NEUTRON-SCATTERING,MEMBRANE-FUSION},
  language     = {eng},
  number       = {3},
  pages        = {277--295},
  publisher    = {Springer},
  series       = {European Physical Journal E. Soft Matter},
  title        = {A comprehensive, time-resolved SANS investigation of temperature-change-induced sponge-to-lamellar and lamellar-to-sponge phase transformations in comparison with 2H -NMR results},
  url          = {http://dx.doi.org/10.1140/epje/i2007-10238-8},
  volume       = {24},
  year         = {2007},
}