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Nanometric sieving of polymer coils by a lamellar liquid crystal: Surfactant AOT and polydimethylacrylamide

Pacios, I E; Renamayor, C S; Horta, A; Thuresson, Krister LU and Lindman, Björn LU (2005) In Macromolecules 38(5). p.1949-1957
Abstract
The liquid crystal formed by surfactant AOT/water mixtures in its lamellar mesophase at a spacing between lamellae, d, equal to 8 nm, is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight in the range M-n= 2-20 x 10(3); the polymers are synthesized by living radical polymerization. The lowest molecular weights do not affect d significantly, indicating that the polymer coils penetrate inside the lamellar phase and dissolve in the water layers. With higher molecular weights, d decreases with added polymer, this decrease being stronger as the molecular weight of the polymer is higher, and the mixture becomes microheterogeneous. This indicates that the higher-molecular-weight polymers are segregated in a separate... (More)
The liquid crystal formed by surfactant AOT/water mixtures in its lamellar mesophase at a spacing between lamellae, d, equal to 8 nm, is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight in the range M-n= 2-20 x 10(3); the polymers are synthesized by living radical polymerization. The lowest molecular weights do not affect d significantly, indicating that the polymer coils penetrate inside the lamellar phase and dissolve in the water layers. With higher molecular weights, d decreases with added polymer, this decrease being stronger as the molecular weight of the polymer is higher, and the mixture becomes microheterogeneous. This indicates that the higher-molecular-weight polymers are segregated in a separate microphase that partially deswells the lamellae and that this segregation increases with the molecular weight of the polymer. The law, which governs the deswelling of lamella with added polymer, is deduced assuming that a fraction of each polymer can dissolve in the lamellar phase, while the rest of the polymer is segregated from it. This latter fraction is then obtained for each polymer simply by fitting to this law the experimental d as function of polymer concentration. It is proposed that the reason for this fractionation of polymer is that the lamellar structure acts as a grating which sieves the polymer coils according to their size relative to d, chains with molecular weight above a certain cutoff value, determined by d, being excluded from the interlamellar space. The fraction of chains excluded from the lamellae is calculated comparing the experimental molecular weight distributions (from SEC) of the polymers with the cutoff values determined by d. The results show that the polymer samples synthesized here cover the whole spectrum of behaviors, from almost total penetration to almost total exclusion. Both this method of cutting off the molecular weight distribution according to d and the other method of fitting d to the law for lamellar deswelling give similar results for the fraction of polymer that is segregated from the lamellae. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Macromolecules
volume
38
issue
5
pages
1949 - 1957
publisher
The American Chemical Society
external identifiers
  • wos:000227448200057
  • scopus:15244353286
ISSN
0024-9297
DOI
10.1021/ma048178j
language
English
LU publication?
yes
id
d23a75ae-15f4-4bec-80ba-1f056c979ad0 (old id 157538)
date added to LUP
2007-07-12 09:24:51
date last changed
2017-01-01 05:06:51
@article{d23a75ae-15f4-4bec-80ba-1f056c979ad0,
  abstract     = {The liquid crystal formed by surfactant AOT/water mixtures in its lamellar mesophase at a spacing between lamellae, d, equal to 8 nm, is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight in the range M-n= 2-20 x 10(3); the polymers are synthesized by living radical polymerization. The lowest molecular weights do not affect d significantly, indicating that the polymer coils penetrate inside the lamellar phase and dissolve in the water layers. With higher molecular weights, d decreases with added polymer, this decrease being stronger as the molecular weight of the polymer is higher, and the mixture becomes microheterogeneous. This indicates that the higher-molecular-weight polymers are segregated in a separate microphase that partially deswells the lamellae and that this segregation increases with the molecular weight of the polymer. The law, which governs the deswelling of lamella with added polymer, is deduced assuming that a fraction of each polymer can dissolve in the lamellar phase, while the rest of the polymer is segregated from it. This latter fraction is then obtained for each polymer simply by fitting to this law the experimental d as function of polymer concentration. It is proposed that the reason for this fractionation of polymer is that the lamellar structure acts as a grating which sieves the polymer coils according to their size relative to d, chains with molecular weight above a certain cutoff value, determined by d, being excluded from the interlamellar space. The fraction of chains excluded from the lamellae is calculated comparing the experimental molecular weight distributions (from SEC) of the polymers with the cutoff values determined by d. The results show that the polymer samples synthesized here cover the whole spectrum of behaviors, from almost total penetration to almost total exclusion. Both this method of cutting off the molecular weight distribution according to d and the other method of fitting d to the law for lamellar deswelling give similar results for the fraction of polymer that is segregated from the lamellae.},
  author       = {Pacios, I E and Renamayor, C S and Horta, A and Thuresson, Krister and Lindman, Björn},
  issn         = {0024-9297},
  language     = {eng},
  number       = {5},
  pages        = {1949--1957},
  publisher    = {The American Chemical Society},
  series       = {Macromolecules},
  title        = {Nanometric sieving of polymer coils by a lamellar liquid crystal: Surfactant AOT and polydimethylacrylamide},
  url          = {http://dx.doi.org/10.1021/ma048178j},
  volume       = {38},
  year         = {2005},
}