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- Lundström-Hämälä, Lisa, et al.
(author)
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Polyelectrolyte Multilayers from Cationic and Anionic Starch : Influence of Charge Density and Salt Concentration on the Properties of the Adsorbed Layers
- 2010
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In: Starke (Weinheim). - : Wiley. - 0038-9056 .- 1521-379X. ; 62:2, s. 102-114
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Journal article (peer-reviewed)abstract
- The purpose of the present work was for identify limits for the formation of stable polyelectrolyte multilayers (PEMs) from cationic and anionic starches (with degrees of substitution of 0.04-0.09) on SiO2 surfaces, taking account of the effect of the charge density of the starches and the salt concentration in the surrounding water phase. The experiments were performed at a pH of 6.3 using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). From these experiments it was concluded that it is possible to form PEMs by the adsorption of oppositely charged starches on SiO2 surfaces; it was also found that adsorption of the first layer is controlled both by electrostatic, non-ionic interactions and by pure steric restrictions, Le, geometrical restrictions, at the surface. The results also indicate that the charge density of the starch must exceed a certain value to allow multilayer formation and that this critical charge density increases with increasing salt concentration. The combination of charge densities of the cationic/anionic starches was also found to influence the adsorption behaviour, and the formed polyelectrolyte multilayers had a high water content of 69-92%.
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| 2. |
- Lundström-Hämälä, Lisa, et al.
(author)
-
Polyelectrolyte multilayers from cationic and anionic starch
- 2010
-
In: Starch/Staerke. - : Wiley. - 0038-9056. ; 62:2, s. 102-114
-
Journal article (peer-reviewed)abstract
- The purpose of the present work was for identify limits for the formation of stable polyelectrolyte multilayers (PEMs) from cationic and anionic starches (with degrees of substitution of 0.04-0.09) on SiO2 surfaces, taking account of the effect of the charge density of the starches and the salt concentration in the surrounding water phase. The experiments were performed at a pH of 6.3 using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). From these experiments it was concluded that it is possible to form PEMs by the adsorption of oppositely charged starches on SiO2 surfaces; it was also found that adsorption of the first layer is controlled both by electrostatic, non-ionic interactions and by pure steric restrictions, i.e. geometrical restrictions, at the surface. The results also indicate that the charge density of the starch must exceed a certain value to allow multilayer formation and that this critical charge density increases with increasing salt concentration. The combination of charge densities of the cationic/anionic starches was also found to influence the adsorption behaviour, and the formed polyelectrolyte multilayers had a high water content of 69-92%. © 2010 WILEY-VCH Verlag GmbH & Co.KGaA, Weinheim.
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| 3. |
- Lundström-Hämälä, Lisa, et al.
(author)
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The adsorption of polyelectrolyte multilayers (PEM) of starch on mechanical pulps for improved mechanical paper properties
- 2009
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In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:4, s. 459-468
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Journal article (peer-reviewed)abstract
- In the present work, the long fibre and middle fibre fraction of a thermomechanical pulp (TMP) was treated with polyelectrolyte multilayers (PEMs) of cationic and anionic starch and sheets were made from both the treated and untreated fractions. In separate experiments, different amounts of untreated fines were added to the PEM-treated fraction before sheets were prepared, and the results were also compared with PEM treatment of the entire pulp containing 17% fines before sheet preparation. The PEMs were made of two different combinations of starch, two cationic potato starches with DS values of 0.06 and 0.09, both in combination with an anionic potato starch with a DS of 0.04, at 0.010 M NaCl and pH 6.3. Sheets were formed using the Rapid Kothen sheet former and the resulting mechanical and optical sheet properties were evaluated. Four-layer PEM treatment of the long fibre and middle fraction resulted in significant improvements in in-plane and out-of-plane mechanical properties. However, a subsequent fines addition reduced the effect of the PEMs, and this is explained by a blocking of the necessary PEM interaction with the treated TMP long fibre and middle fraction by the subsequently added fines. PEM treatment of the entire pulp increased the amount of starch needed for PEM treatment, but improved the in-plane and out-of-plane mechanical properties compared with those of sheets prepared from a PEM-treated long fibre and middle fraction with a subsequent addition of fine material. The increase in the tensile index for sheets made from a PEM-treated long fibre and the middle fraction without a subsequent fines addition, however, was much larger.
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