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| 2. |
- Sennerfors, T, et al.
(författare)
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Adsorption of polyelectrolyte and nanoparticles at the silica-aqueous solution interface: Influence of the history of additions of the two components
- 2001
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 237, s. 129-135
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial properties of a mixed system of low-charged cationic polyelectrolyte and silica nanoparticles has been studied by means of ellipsometry. Special attention was devoted to the effect that the order of addition of the two components has on the adsorption behavior of the mixed system. Adsorption on silica was in one case studied after simultaneous addition of the components to the aqueous solution. The measured adsorption rates were then much slower than expected for a mass-transfer limited process. This behavior signifies the presence of an electrosteric barrier arising due to preadsorbed polymer-particle complexes. Interfacial layers containing particles were at plateau conditions shown to be highly swollen, whereas the cationic polymer in the particle-free systems adopted a more flat surface conformation. The layer thickness was observed to monotonously increase with an increasing presence of nanoparticles in solution, while the surface excess showed a maximum at intermediate values. The finding was rationalized by the competition between particles and the surface for polymer charges leading to swelling and a decreased effective interaction between polymer and surface. In the other case studied, when polyelectrolyte and nanoparticles were added sequentially, a much more rapid concentration-dependent adsorption was observed. The kinetic adsorption barrier for nonassociated particles was clearly negligible compared with that for the polymer-particle complex. The surface excess did not exhibit an adsorption maximum as a function of added nanoparticles in this situation, indicating that the polymer layer to some degree is irreversibly anchored at the silica surface. Some implications of the above findings for practical papermaking using multicomponent retention systems are put forward
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| 3. |
- Sennerfors, T, et al.
(författare)
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Adsorption of polyelectrolyte-nanoparticle systems on silica: Influence of ionic strength
- 2002
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 254, s. 222-226
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Tidskriftsartikel (refereegranskat)abstract
- In this work the effect of ionic strength on the adsorption behavior of cationic polyelectrolyte (acrylamide-acrylamidopropyltrimethylammonium chloride) and negatively charged silica particles has been studied by means of ellipsometry. The adsorption of the polyelectrolyte was observed to increase with increasing salt concentration, a behavior typical for polyelectrolytes with a screening-reduced solvency and a nonelectrostatic affinity for the surface. A similar dependence on the ionic strength was observed when studying the electrolyte effect on the nanoparticle adsorption to the preadsorbed polyelectrolyte film, suggesting that the polyelectrolyte surface conformations largely govern the binding capacity of the particles to the surface
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| 4. |
- Sennerfors, T, et al.
(författare)
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Adsorption of polyelectrolyte-nanoparticle systems on silica: Influence on interaction forces
- 2000
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 228, s. 127-134
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have studied the interfacial properties of cationic polyelectrolyte (PE) and silica nanoparticle (NP) systems at macroscopic silica surfaces by means of ellipsometry. The influence of adsorbed layers on the interactions between silica surfaces was also investigated using the bimorph surface force apparatus. Added nanoparticles were observed to strongly swell the interfacial polyelectrolyte layers, an effect partly related to neutralisation of charged polyelectrolyte groups. The effect was more pronounced for low than highly charged polyelectrolytes. Overall, the presence of nanoparticles seemed to increase the repulsive interaction measured between silica surfaces. The force measured on approach was long-range and quite strongly repulsive. On separation, an attractive bridging interaction was measured for polyelectrolyte covered surfaces. For the low charged polyelectrolyte used in the study, the force turned repulsive on addition of nanoparticles. For the highly charged polyelectrolyte used, a change from a very strong attraction (involving a jump of the surfaces out of contact) to a very long-range elastic attractive force was observed on adding nanoparticles. The long-range elastic force indicates that polymer chains and nanoparticles form a transient network in the gap between the surfaces. The observed difference in the outward force curves may explain why the addition of nanoparticles appears to improve e.g., shear-resistance and re-flocculation characteristics of polymeric flocculants.
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| 5. |
- Sennerfors, T, et al.
(författare)
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Formation, chemical composition, and structure of polyelectrolyte-nanoparticle multilayer films
- 2002
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 18, s. 6410-6415
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Tidskriftsartikel (refereegranskat)abstract
- The buildup and structure of multilayer films containing cationic polyelectrolyte and silica nanoparticles have been studied by means of ellipsometry, atomic force microscopy, and X-ray photoelectron spectroscopy. Emphasis was placed on the effect of ionic strength on the adsorption behavior and structure formation. Consecutive exposure of a silica substrate to low ionic strength solutions containing polyelectrolyte and nanoparticles resulted in the formation of stable adsorbed films with a reproducible stratified multilayer structure. The films formed in high ionic strength solutions were initially much thicker but also clearly less stable. A significant desorption was observed to take place in conjunction with the second exposure to silica nanoparticles. The effect of electrolyte concentration is discussed in terms of a salt-induced glass-liquid transition, above which the relaxation rate in the adsorbed composite film increases and thereby hinders the formation of multilayer structures
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