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Time- and Space-Resolved SAXS Experiments Inform on Phase Transition Kinetics in Hydrated, Liquid-Crystalline Films of Polyion-Surfactant Ion "complex Salts"

Li, Joaquim LU ; Gustavsson, Charlotte and Piculell, Lennart LU (2016) In Langmuir 32(20). p.5102-5110
Abstract

Detailed time- and space-resolved SAXS experiments show the variation with hydration of liquid crystalline structures in ethanol-cast 5-80 μm thick films of polyion-surfactant ion "complex salts" (CS). The CS were dodecyl- (C12) or hexadecyl- (C16) trimethylammonium surfactants with polyacrylate (DP 25 or 6000) counter-polyions. The experiments were carried out on vertical films in humid air above a movable water bath, so that gradients of hydration were generated, which could rapidly be altered. Scans over different positions along a film, kept fixed relative to the bath, showed that the surfactant aggregates of the various liquid-crystalline CS structures grow in cross-sectional area with decreasing hydration.... (More)

Detailed time- and space-resolved SAXS experiments show the variation with hydration of liquid crystalline structures in ethanol-cast 5-80 μm thick films of polyion-surfactant ion "complex salts" (CS). The CS were dodecyl- (C12) or hexadecyl- (C16) trimethylammonium surfactants with polyacrylate (DP 25 or 6000) counter-polyions. The experiments were carried out on vertical films in humid air above a movable water bath, so that gradients of hydration were generated, which could rapidly be altered. Scans over different positions along a film, kept fixed relative to the bath, showed that the surfactant aggregates of the various liquid-crystalline CS structures grow in cross-sectional area with decreasing hydration. This behavior is attributed to the low water content. Studies of films undergoing rapid dehydration, made possible by the original experimental setup, gave strong evidence that some of the investigated systems remain kinetically trapped for minutes in a nonequilibrium Pm3n micellar cubic phase before switching to the equilibrium P6mm 2D hexagonal phase. Both the length of the polyion and the length of the surfactant hydrocarbon "tail" affect the kinetics of the phase transition. The slowness of the cubic-to-hexagonal structural transition is attributed to the fact that it requires major rearrangements of the polyions and surfactant ions relative to each other. By contrast, other structure changes, such as between the hexagonal and rectangular phases, were observed to occur much more rapidly.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
32
issue
20
pages
9 pages
publisher
The American Chemical Society
external identifiers
  • Scopus:84971280691
ISSN
0743-7463
DOI
10.1021/acs.langmuir.6b00935
language
English
LU publication?
yes
id
fbd0aeea-f973-431d-bf68-56bc527ac26b
date added to LUP
2016-06-28 11:21:47
date last changed
2016-10-13 05:10:57
@misc{fbd0aeea-f973-431d-bf68-56bc527ac26b,
  abstract     = {<p>Detailed time- and space-resolved SAXS experiments show the variation with hydration of liquid crystalline structures in ethanol-cast 5-80 μm thick films of polyion-surfactant ion "complex salts" (CS). The CS were dodecyl- (C<sub>12</sub>) or hexadecyl- (C<sub>16</sub>) trimethylammonium surfactants with polyacrylate (DP 25 or 6000) counter-polyions. The experiments were carried out on vertical films in humid air above a movable water bath, so that gradients of hydration were generated, which could rapidly be altered. Scans over different positions along a film, kept fixed relative to the bath, showed that the surfactant aggregates of the various liquid-crystalline CS structures grow in cross-sectional area with decreasing hydration. This behavior is attributed to the low water content. Studies of films undergoing rapid dehydration, made possible by the original experimental setup, gave strong evidence that some of the investigated systems remain kinetically trapped for minutes in a nonequilibrium Pm3n micellar cubic phase before switching to the equilibrium P6mm 2D hexagonal phase. Both the length of the polyion and the length of the surfactant hydrocarbon "tail" affect the kinetics of the phase transition. The slowness of the cubic-to-hexagonal structural transition is attributed to the fact that it requires major rearrangements of the polyions and surfactant ions relative to each other. By contrast, other structure changes, such as between the hexagonal and rectangular phases, were observed to occur much more rapidly.</p>},
  author       = {Li, Joaquim and Gustavsson, Charlotte and Piculell, Lennart},
  issn         = {0743-7463},
  language     = {eng},
  month        = {05},
  number       = {20},
  pages        = {5102--5110},
  publisher    = {ARRAY(0x90298b8)},
  series       = {Langmuir},
  title        = {Time- and Space-Resolved SAXS Experiments Inform on Phase Transition Kinetics in Hydrated, Liquid-Crystalline Films of Polyion-Surfactant Ion "complex Salts"},
  url          = {http://dx.doi.org/10.1021/acs.langmuir.6b00935},
  volume       = {32},
  year         = {2016},
}