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Self assembly of surfactants and polyelectrolytes in solution and at interfaces
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
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 [en]
Surfactant, polyelectrolyte, small–angle neutron scattering, static light scattering, dynamic light scattering, polyelectrolyte–surfactant association, protein
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-425ISBN: 91-7178-127-7 (print)OAI: oai:DiVA.org:kth-425DiVA: diva2:11455
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
List of papers
1. Interactions between mucin and alkyl sodium sulfates in solution: a light scattering study
Open this publication in new window or tab >>Interactions between mucin and alkyl sodium sulfates in solution: a light scattering study
2002 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 10, 3848-3853 p.Article in journal (Refereed) Published
Abstract [en]

The properties of negatively charged mucin in aqueous solutions and its interaction with anionic sodium alkyl sulfates with different hydrocarbon chain lengths were studied by means of dynamic light scattering. It was observed that mucin forms aggregates in aqueous solutions with a hydrodynamic radius above 500 nm. These aggregates dissolve when sodium dodecyl sulfate or sodium decyl sulfate is present at sufficiently high concentration, above about 0.2 cmc (critical micellar concentration). On the other hand, sodium octyl sulfate is not very effective in dissolving the mucin aggregates. The hydrodynamic radius of the dissolved mucin, decorated with some associated surfactant, is found to be in the range of 40-90 nm. The observation that the dissolving power of the sodium alkyl sulfates decreases with decreasing surfactant chain length suggests that the association between the surfactant and mucin is hydrophobically driven. The kinetics of the dissolution process depends on the surfactant concentration, a higher surfactant concentration giving rise to a more rapid dissolution of the aggregates. It was also observed that when the ionic strength is increased, the surfactant concentration needed to dissolve the mucin aggregates decreases. This can be explained by reduction of repulsive electrostatic forces by the salt.

Keyword
Aggregates, Electrostatics, Hydrocarbons, Light scattering, Surface active agents, Hydrocarbon chains, Proteins
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-6672 (URN)10.1021/la015717u (DOI)000175500300015 ()
Note
QC 20100901. Uppdaterad från In press till Published 20100901.Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
2. Interactions between Mucin and Surfactants at Solid-Liquid Interfaces
Open this publication in new window or tab >>Interactions between Mucin and Surfactants at Solid-Liquid Interfaces
2002 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 24, 9383-9392 p.Article in journal (Refereed) Published
Abstract [en]

The association between mucin and surfactants at the solid-liquid interface has been investigated employing reflectometry. The study is particularly aimed at understanding the removal of preadsorbed mucin layers by surfactant addition. To this end we investigated the effect of three different surfactants, one anionic surfactant, sodium dodecylsulfate (SDS), and two nonionic ones, penta(oxy ethylene) dodecyl ether (C12E5) and n-dodecyl beta-D-maltopyranoside (C-12-mal), All three surfactants were found to be potent in removing mucin from hydrophobic surfaces. On the otherhand, C-12-mal was found to have a very limited effect on mucin adsorbed to hydrophilic negatively charged surfaces, whereas the mucin layer was removed by SDS and C12E5. The association between mucin and the three different surfactants was also investigated by means of dynamic light scattering and surface tension measurements. It was concluded that SDS associates readily with mucin above a critical surfactant concentration, about 0.2 cmc, whereas the nonionic surfactants associate with mucin to a very limited degree. The results obtained with the different techniques allow us to propose that C12E5 removes mucin from silica surfaces by competitive adsorption, whereas the removal of mucin by SDS is due to formation of mucin/SDS complexes that have reduced surface affinity and increased water solubility compared to mucin alone.

Keyword
Addition reactions, Adsorption, Association reactions, Composition effects, Hydrophilicity, Hydrophobicity, Light scattering, Molecular dynamics, Reflectometers, Solubility, Surface active agents, Surface tension, Anionic surfactant, Mucin, Reflectometry, Sodium dodecylsulfate, Interfaces (materials)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-6673 (URN)10.1021/la0259813 (DOI)000179428400039 ()
Note
QC 20100901Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
3. The structures of complexes between polyethylene imine and sodium dodecyl sulfate in D2O: a scattering study
Open this publication in new window or tab >>The structures of complexes between polyethylene imine and sodium dodecyl sulfate in D2O: a scattering study
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.

Keyword
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:nbn:se:kth:diva-14453 (URN)10.1021/jp046837o (DOI)000226213200030 ()2-s2.0-12344296748 (Scopus ID)
Note
QC 20100901Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
4. Deuterium isotope effects on the interaction between hyperbranched polyethylene imine and an anionic surfactant
Open this publication in new window or tab >>Deuterium isotope effects on the interaction between hyperbranched polyethylene imine and an anionic surfactant
Show others...
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 33, 16196-16202 p.Article in journal (Refereed) Published
Abstract [en]

Solvent isotope effects on the interaction between the hyperbranched cationic polyelectrolyte, polyethylene imine (PEI), and the anionic surfactant sodium dodecyl sulfate (SDS) were investigated using potentiometric titration and eletrophoretic mobility measurements. In the basic pH range, a significantly higher fraction of the amine groups was found to be protonated when the PEI was dissolved in D2O compared to H2O at the same pH/pD. The difference in polymer charge in the two solvents decreases gradually with decreasing pH, and it completely diminishes at around pH = 4. Electrophoretic mobility measurements of PEI/SDS complexes at different pH values correlated very well with these observations. At pH/pD approximate to 9 a much higher mobility of the PEI/SDS complexes was found in D2O than in H2O at low surfactant concentrations, and the charge neutralization point shifted to a considerably larger surfactant concentration in heavy water. These results can be explained by the significantly higher charge density of the PEI in D2O compared to H2O. However, at the natural pH/pD as well as at pH = 4 and pD = 4 conditions the PEI molecules have roughly equal charge densities, which result in very similar charged characteristics (mobilities) of the PEI/SDS complexes as well as the same charge neutralization SDS concentration. It can be concluded that extreme care must be taken in the general analysis of those experiments in which weak polyelectrolyte/surfactant aggregates are investigated in heavy water, and then these observations are correlated with structures of the same system in water.

Keyword
Complexation, Deuterium, Electrophoresis, Heavy water, Negative ions, Organic polymers, pH effects, Polyelectrolytes, Sodium compounds, Solvents, Surface active agents, Titration, Anionic surfactants, Polyethylene imines (PEI), Sodium dodecyl sulfate (SDS), Solvent isotope effects, Molecular dynamics
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-6675 (URN)10.1021/jp052222v (DOI)000231426000074 ()2-s2.0-24944481597 (Scopus ID)
Note
QC 20100901Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
5. A small-angle neutron and static light scattering study of micelles formed in aqueous mixtures of a nonionic alkylglucoside and an anionic surfactant
Open this publication in new window or tab >>A small-angle neutron and static light scattering study of micelles formed in aqueous mixtures of a nonionic alkylglucoside and an anionic surfactant
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 25, 12387-12393 p.Article in journal (Refereed) Published
Abstract [en]

The size and shape of micelles formed in aqueous mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic sugar-based surfactant n-decyl beta-D-glucopyranoside (C(10)G) at different concentrations of added salt have been investigated with small-angle neutron and static light scattering. Rather small prolate ellipsoidal micelles form in the absence of added salt and at [NaCl] = 10 mM in D2O. The micelles grow considerably in length to large rods as the electrolyte concentration is raised to [NaCl] = 0.1 M. In excess of nonionic surfactant ([SDS]/[C(10)G] = 1:3) at [NaCl] = 0.1 M in D2O, several thousands of Angstroms long wormlike micelles are observed. Most interestingly, a conspicuously large isotope solvent effect was observed from static light scattering data according to which micelles formed at [SDS]/[C(10)G] = 1:3 and [NaCl] = 0.1 M in H2O are at least five times smaller than micelles formed in the corresponding samples in D2O.

Keyword
Deuterium, Electrolytes, Hydrophobicity, Light scattering, Negative ions, Neutron scattering, Phase diagrams, Sodium compounds, Surface active agents, Alkylglucoside, Anionic surfactants, Phase boundaries, Sodium dodecyl sulfate (SDS), Micelles, glucose, ion, surfactant, alkylation, article, chemistry, micelle, neutron, Alkylation, Glucose, Ions, Micelles, Neutrons, Surface-Active Agents
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-6676 (URN)10.1021/jp051113d (DOI)000230122900025 ()2-s2.0-22744454078 (Scopus ID)
Note
QC 20100901. Tidigare titel: A Small-Angle Neutron Scattering Study of Micelles Formed in Aqueous Mixtures of Nonionic Alkylglucoside and an Anionic Surfactant. Titel ändrad 20100901.Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
6. Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR
Open this publication in new window or tab >>Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR
Show others...
2007 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, no 1, 21-33 p.Article in journal (Refereed) Published
Abstract [en]

A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PE045MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.

Keyword
comb polymer; comb polyelectrolyte; polymer-surfactant association; polyelectrolyte-surfactant aggregate; small-angle neutron scattering; light scattering; NMR; surface tension; polyelectrolyte; surfactant; SDS
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-6677 (URN)10.1016/j.jcis.2006.09.004 (DOI)000247286100004 ()2-s2.0-34249817580 (Scopus ID)
Note
QC 20100813. Uppdaterad från submitted till published (20100813).Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
7. Chitosan-SDS association probed by Small-Angle Neutron Scattering
Open this publication in new window or tab >>Chitosan-SDS association probed by Small-Angle Neutron Scattering
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-6678 (URN)
Note
QC 20100617Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2010-09-01Bibliographically approved

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