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The structures of complexes between polyethylene imine and sodium dodecyl sulfate in D2O: a scattering study
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
GKSS Research Centre, Geesthacht.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 1, 167-174 p.Article in journal (Refereed) Published
Abstract [en]

The association between a highly branched polyelectrolyte with ionizable groups, polyethylene imine (PEI), and an anionic surfactant, sodium dodecyl sulfate (SDS), has been investigated at two pH values, using small-angle neutron and light scattering. The scattering data allow us to obtain a detailed picture of the association structures formed. Small-angle neutron scattering (SANS) measurements in solutions containing highly charged PEI at low pH and low SDS concentrations indicate the presence of disklike aggregates. The aggregates change to a more complex three-dimensional structure with increasing surfactant concentration. One pronounced feature in the scattering curves is the presence of a Bragg-like peak at high q-values observed at a surfactant concentration of 4.2 mM and above. This scattering feature is attributed to the formation of a common well-ordered PEI/SDS structure, in analogue to what has been reported for other polyelectrolyte-surfactant systems. Precipitation occurred at the charge neutralization point, and X-ray diffraction measurements on the precipitate confirmed the existence of an ordered structure within the PEI/SDS aggregates, which was identified as a lamellar internal organization. Polyethylene imine has a low charge density in alkaline solutions. At pH 10.1 and under conditions where the surfactant was contrast matched, the SANS scattering curves showed only small changes with increasing surfactant concentration. This suggests that the polymer acts as a template onto which the surfactant molecules aggregate. Data from both static light scattering and SANS recorded under conditions where SDS and to a lower degree PEI contribute to the scattering were found to be consistent with a structure of stacked elliptic bilayers. These structures increased in size and became more compact as the surfactant concentration was increased up to the charge neutralization point.

Place, publisher, year, edition, pages
2005. Vol. 109, no 1, 167-174 p.
Keyword [en]
angle neutron-scattering, cationic polyelectrolyte, poly(ethylene imine), anionic surfactant, light-scattering, electromotive-force, deuterium-oxide, mixtures, adsorption, microcalorimetry
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-14453DOI: 10.1021/jp046837oISI: 000226213200030Scopus ID: 2-s2.0-12344296748OAI: oai:DiVA.org:kth-14453DiVA: diva2:332494
Note
QC 20100901Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-01Bibliographically approved
In thesis
1. Self assembly of surfactants and polyelectrolytes in solution and at interfaces
Open this publication in new window or tab >>Self assembly of surfactants and polyelectrolytes in solution and at interfaces
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis focuses on the study of the interactions between polyelectrolytes and surfactants in aqueous solutions and at interfaces, as well as on the structural changes these molecules undergo due to that interaction. Small–angle neutron scattering, dynamic, and static light scattering were the main techniques used to investigate the interactions in bulk. The first type of polymer studied was a negatively charge glycoprotein (mucin); its interactions with ionic sodium alkyl sulfate surfactants and nonionic surfactants were determined. This system is of great relevance for several applications such as oral care and pharmaceutical products, since mucin is the main component of the mucus layer that protects the epithelial surfaces (e.g. oral tissues). Sodium dodecyl sulfate (SDS) on the other hand, has been used as foaming agent in tooth pastes for a very long time. In this work it is seen how SDS is very effective in dissolving the large aggregates mucin forms in solution, as well as in removing preadsorbed mucin layers from different surfaces. On the other hand, the nonionic surfactant n-dodecyl β-D-maltopyranoside (C12-mal), does not affect significantly the mucin aggregates in solution, neither does it remove mucin effectively from a negatively charge hydrophilic surface (silica). It can be suggested that nonionic surfactants (like the sugar–based C12-mal) could be used to obtain milder oral care products. The second type of systems consisted of positively charged polyelectrolytes and a negatively charged surfactant (SDS). These systems are relevant to a wide variety of applications ranging from mining and cleaning to gene delivery therapy. It was found that the interactions of these polyelectrolytes with SDS depend strongly on the polyelectrolyte structure, charge density and the solvent composition (pH, ionic strength, and so on). Large solvent isotopic effects were found in the interaction of polyethylene imine (PEI) and SDS, as well as on the interactions of this anionic surfactant and the sugar–based n-decyl β-D-glucopyranoside (C10G1). These surfactants mixtures formed similar structures in solutions to the ones formed by some of the polyelectrolytes studied, i.e. ellipsoidal micelles at low electrolyte concentration and stiff rods, at high electrolyte and SDS concentrations.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 71 p.
Series
Trita-YTK, ISSN 1650-0490 ; 2005:02
Keyword
Surfactant, polyelectrolyte, small–angle neutron scattering, static light scattering, dynamic light scattering, polyelectrolyte–surfactant association, protein
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-425 (URN)91-7178-127-7 (ISBN)
Public defence
2005-09-30, Sal D3, Lindstedtsvägen 5, 09:00
Opponent
Supervisors
Note
QC 20100901Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2010-09-01Bibliographically approved

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