Advanced

Fragmentation of the lamellae and fractionation of polymer coils upon mixing poly(dimethylacrylamide) with the lamellar phase of aerosol OT in water

Pacios, Isabel E; Renamayor, C S; Horta, A; Lindman, Björn LU and Thuresson, Krister LU (2005) In The Journal of Physical Chemistry Part B 109(50). p.23896-23904
Abstract
The lamellar mesophase formed by surfactant 1,4-bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in deuterated water is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight ((M) over bar (n) = (2-20) x 10(3)). The mixtures separate into microphases (lamellar plus isotropic polymer solution). Their microstructures are studied by microscopy, small-angle X-ray scattering (SAXS), and deuterium NMR (2 H NMR). According to SAXS, the lamellar phase fractionates the molecular weight distribution of the polymer, by dissolving only chains with coil sizes smaller than the thickness of the water layers between lamellae, and keeping larger chains segregated from the lamellar phase. The fraction of polymer that is segregated from... (More)
The lamellar mesophase formed by surfactant 1,4-bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in deuterated water is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight ((M) over bar (n) = (2-20) x 10(3)). The mixtures separate into microphases (lamellar plus isotropic polymer solution). Their microstructures are studied by microscopy, small-angle X-ray scattering (SAXS), and deuterium NMR (2 H NMR). According to SAXS, the lamellar phase fractionates the molecular weight distribution of the polymer, by dissolving only chains with coil sizes smaller than the thickness of the water layers between lamellae, and keeping larger chains segregated from the lamellar phase. The fraction of polymer that is segregated from the lamellar phase grows with (M) over bar (n) of the polymer. In H-2 NMR, there are two signals, a quadrupolar doublet (water molecules hydrating the anisotropic lamellar phase contribute to this doublet) and a singlet (water molecules in the isotropic polymer solution contribute to this singlet). These two signals are deconvoluted to analyze the phases. Mixing with the polymer produces the partial dispersion of the lamellar phase into small fragments (microcrystallites). The structure of these microcrystallites is such that they conserve the regular long period spacing of the macrophase, and are thus identified in SAXS, but they are smaller than the minimum size required to produce quadrupolar splitting (about 4 mu m), and therefore, in H-2 NMR, they contribute to the singlet. H-2 NMR can thus not distinguish between small microcrystallites and an isotropic polymer solution segregated from the lamellar phase; instead small microcrystallites are detected as an apparent increase of the isotropic solution. The degree of dispersion produced by the polymer in the lamellar phase is correlated 4 with the degree of segregation that the polymer suffers. Thus, much greater dispersion into microcrystallites is produced by the higher (M) over bar (n) polymers than by the lower (M) over bar (n) polymers (in the range covered by the present samples, although with a much higher molecular weight sample (3 x 10(6)) that is totally segregated no such microcrystallites were detected). (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part B
volume
109
issue
50
pages
23896 - 23904
publisher
The American Chemical Society
external identifiers
  • wos:000234119100018
  • scopus:30544434812
ISSN
1520-5207
DOI
10.1021/jp0539019
language
English
LU publication?
yes
id
3ac9f7b6-e464-42e6-8b86-106c0d87df60 (old id 157531)
date added to LUP
2007-07-12 09:22:52
date last changed
2017-01-01 07:11:02
@article{3ac9f7b6-e464-42e6-8b86-106c0d87df60,
  abstract     = {The lamellar mesophase formed by surfactant 1,4-bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in deuterated water is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight ((M) over bar (n) = (2-20) x 10(3)). The mixtures separate into microphases (lamellar plus isotropic polymer solution). Their microstructures are studied by microscopy, small-angle X-ray scattering (SAXS), and deuterium NMR (2 H NMR). According to SAXS, the lamellar phase fractionates the molecular weight distribution of the polymer, by dissolving only chains with coil sizes smaller than the thickness of the water layers between lamellae, and keeping larger chains segregated from the lamellar phase. The fraction of polymer that is segregated from the lamellar phase grows with (M) over bar (n) of the polymer. In H-2 NMR, there are two signals, a quadrupolar doublet (water molecules hydrating the anisotropic lamellar phase contribute to this doublet) and a singlet (water molecules in the isotropic polymer solution contribute to this singlet). These two signals are deconvoluted to analyze the phases. Mixing with the polymer produces the partial dispersion of the lamellar phase into small fragments (microcrystallites). The structure of these microcrystallites is such that they conserve the regular long period spacing of the macrophase, and are thus identified in SAXS, but they are smaller than the minimum size required to produce quadrupolar splitting (about 4 mu m), and therefore, in H-2 NMR, they contribute to the singlet. H-2 NMR can thus not distinguish between small microcrystallites and an isotropic polymer solution segregated from the lamellar phase; instead small microcrystallites are detected as an apparent increase of the isotropic solution. The degree of dispersion produced by the polymer in the lamellar phase is correlated 4 with the degree of segregation that the polymer suffers. Thus, much greater dispersion into microcrystallites is produced by the higher (M) over bar (n) polymers than by the lower (M) over bar (n) polymers (in the range covered by the present samples, although with a much higher molecular weight sample (3 x 10(6)) that is totally segregated no such microcrystallites were detected).},
  author       = {Pacios, Isabel E and Renamayor, C S and Horta, A and Lindman, Björn and Thuresson, Krister},
  issn         = {1520-5207},
  language     = {eng},
  number       = {50},
  pages        = {23896--23904},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {Fragmentation of the lamellae and fractionation of polymer coils upon mixing poly(dimethylacrylamide) with the lamellar phase of aerosol OT in water},
  url          = {http://dx.doi.org/10.1021/jp0539019},
  volume       = {109},
  year         = {2005},
}