| 1. |
- Ondaral, Sedat, et al.
(författare)
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FIXATION OF DISSOLVED AND COLLOIDAL SUBSTANCES ON FIBERS AND SILICON OXIDE SURFACES USING WATER SOLUBLE CROSSLINKED CATIONIC POLYMERS
- 2008
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Ingår i: Cellulose Chemistry and Technology. - 0576-9787. ; 42:1-3, s. 61-69
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of water soluble crosslinked cationic polymers (CCP) in the fixation of dissolved and colloidal substances (DCS) onto fibers was investigated. Two different types of CCP were synthesized by dispersion polymerization of acrylamide (AAm) and diallyldimethylammonium chloride (DADMAC), with N,N'-methylene-bis-acrylamide (MBA) as a crosslinker. Relative turbidity, zeta potential and average diameter of the colloidal particles were determined to monitor their performance in DCS fixation. The results indicated that both polymers were able to fix a maximum amount of DCS particles onto fibers around a zero zeta potential, most probably clue to a patch-type flocculation mechanism. The conclusion reached was that flocculation was significant while the particles still had a negative zeta potential. The aggregation mechanism of a fiber-free DCS suspension occurred as Charge neutralisation, changed, by the addition of 10 mM NaCl to a patch-type mechanism. The CCPI consumption necessary to attain a maximum DCS removal was lower than the CCP2 consumption, as ascribed to the higher charge density and higher molecular mass of this polymer. The experiments performed on a quartz crystal microbalance equipment with dissipation (QCM-D) showed that the adsorbed charge and layer thickness of the polymers significantly affected fixation of the DCS particles onto the pre-adsorbed polymer layers on the SiO2 surface.
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| 2. |
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| 3. |
- Ankerfors, Caroline, et al.
(författare)
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Using jet mixing to prepare polyelectrolyte complexes : Complex properties and their interaction with silicon oxide surfaces
- 2010
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 351:1, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- The influence of mixing procedure on the properties of polyelectrolyte complexes (PECs) was investigated using two complexation techniques, polyelectrolyte titration and jet mixing, the latter being a new method for PEC preparation. For the low-molecular-weight polyelectrolytes polyacrylic acid (PAA) and polyallyl amine hydrochloride (PAH), shorter mixing times produced smaller PECs, whereas for higher molecular weights of the same polyelectrolytes, PEC size first decreased with decreasing mixing time to a certain level, after which it started increasing again. This pattern was likely due to the diffusion-controlled formation of "pre-complexes", which, in the case of low-molecular-weight polymers, occurs sufficiently quickly to form stable complexes; when polyelectrolytes are larger, however, non-equilibrium pre-complexes, more prone to aggregation, are formed. Comparing the techniques revealed that jet mixing produced smaller complexes, allowing PEC size to be controlled by mixing time, which was not the case with polyelectrolyte titration. Higher polyelectrolyte concentration during jet mixing led to the formation of larger PECs. It was also demonstrated that PEC size could be changed after preparation: increasing the pH of the PEC dispersion led to an irreversible increase in PEC size, whereas lowering the pH did not influence PEC size. The adsorption behavior of PECs formed from weak polyelectrolytes on model substrates was studied using QCM-D, SPAR, and AFM imaging; the results indicated that increasing the pH increased the amount of PECs adsorbed to model surfaces. However, the amount of PECs adsorbed to the model surfaces was low compared with other systems in all studied cases.
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| 4. |
- Benselfelt, Tobias, et al.
(författare)
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Adsorption of Xyloglucan onto Cellulose Surfaces of Different Morphologies : An Entropy-Driven Process
- 2016
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 17:9, s. 2801-2811
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Tidskriftsartikel (refereegranskat)abstract
- The temperature-dependence of xyloglucan (XG) adsorption onto smooth cellulose model films regenerated from N-methylmorpholine N-oxide (NMMO) was investigated using surface plasmon resonance spectroscopy, and it was found that the adsorbed amount increased with increasing temperature. This implies that the adsorption of XG to NMMO-regenerated cellulose is endothermic and supports the hypothesis that the adsorption of XG onto cellulose is an entropy-driven process. We suggest that XG adsorption is mainly driven by the release of water molecules from the highly hydrated cellulose surfaces and from the XG molecules, rather than through hydrogen bonding and van der Waals forces as previously suggested. To test this hypothesis, the adsorption of XG onto cellulose was studied using cellulose films with different morphologies prepared from cellulose nanocrystals (CNC), semicrystalline NMMO-regenerated cellulose, and amorphous cellulose regenerated from lithium chloride/dimethylacetamide. The total amount of high molecular weight xyloglucan (XGHMW) adsorbed was studied by quartz crystal microbalance and reflectometry measurements, and it was found that the adsorption was greatest on the amorphous cellulose followed by the CNC and NMMO-regenerated cellulose films. There was a significant correlation between the cellulose dry film thickness and the adsorbed XG amount, indicating that XG penetrated into the films. There was also a correlation between the swelling of the films and the adsorbed amounts and conformation of XG, which further strengthened the conclusion that the water content and the subsequent release of the water upon adsorption are important components of the adsorption process.
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| 5. |
- Ondaral, Sedat, et al.
(författare)
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Surface-Induced Rearrangement of Polyelectrolyte Complexes : Influence of Complex Composition on Adsorbed Layer Properties
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:18, s. 14606-14614
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption characteristics of two different types of polyelectrolyte complexes (PECs). prepared by mixing poly(allylamine hydrochloride) and poly(acrylic acid) in a confined impinging jet (CIJ) mixer, have been investigated with the aid of stagnation point adsorption reflectometry (SPAR), a quartz crystal microbalance with dissipation (QCM-D), and atomic force microscopy (A FM) using SiO2 surfaces The two sets of PEC were prepared by combining high molecular mass PAH/FAA (PEC-A) and low molt:cubit mass PAH/PAA (PEC-B) The PEC-A showed a higher adsorption to the SiO2 surfaces than the PEC-B The adsorption of the PEC-A also showed a larger change in the dissipation (AD), according to the QCM-D measurements, suggesting that the adsorbed layer of these complexes had a relatively lower viscosity and a lower shear modulus Complementary investigations of the adsorbed layer using A FM imaging showed that the adsorbed layer of PEC-A was significantly different from that of PEC-B and that the changes in properties with adsorption time were very different for the two types of PECs The PEC-A complexes showed a coalescence into larger block of complexes on the SiO2 surface, but this was not detected with the PEC-B The size determinations of the complexes in solution showed that they were very stable over time, and it was therefore concluded that the coalescence of the complexes was induced I the interaction between the complexes and the surface The results also indicated that polyelectrolytes can migrate between the different complexes adsorbed to the surface The results also give indications that the preparation of PEC-B leads to the formation of two different types of polyelectrolyte complexes differing in the amount of polymer in the complexes: i.e., two populations of complexes were formed with similar sizes but with totally different adsorption structures at the solid-liquid interface.
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| 6. |
- Ondaral, Sedat, et al.
(författare)
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The adsorption of hyperbranched polymers on silicon oxide surfaces
- 2006
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 301:1, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- The electrostatic interaction between quarternised hyperbranched polymers (polyesteramides) and a silicon oxide (SiO2) surface has been studied via adsorption studies with quartz crystal microbalance instrument with dissipation (QCM-D). Frequency shift (Delta f) results show that the increase in both pH and salt concentration positively affect the adsorbed amount of these polymers, calculated by Sauerbrey equation, on the QCM crystal. The adsorbed amount of HA1 (with lower molecular weight and higher charge density) was lower than that of HA2 (with higher molecular weight and lower charge density) in all experiments. It was also observed that there are no significant changes in the dissipation after adsorption of these polymers. This indicated that both hyperbranched polymers formed rigid adsorbed layers on the negative SiO2 surface. Additionally, the results were compared with adsorption of poly-DADMAC and the results showed that the hyperbranched polymers formed thicker and more rigid layers as compared with the poly-DADMAC.
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| 7. |
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| 8. |
- Wågberg, Lars, et al.
(författare)
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Hyperbranched polymers as a fixing agent for dissolved and colloidal substances on fiber and SIO2 surfaces
- 2007
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 46:7, s. 2212-2219
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Tidskriftsartikel (refereegranskat)abstract
- Hyperbranched polymers (polyesteramides) were used as a cationic fixing agent to remove dissolved and colloidal substances (DCS) from the water phase in a fiber suspension. The relative turbidity, electrophoretic mobility, and average diameter of the colloidal particles were determined as a function of polyelectrolyte concentration. The results indicated that maximum removal of DCS was achieved at about zero electrophoretic mobility of the suspension where the negative surface charges of particles were neutralized by the oppositely charged hyperbranched polymer. The amount of hyperbranched polymers needed to maximize DCS fixation on the fibers was higher than the amount of poly-DADMAC (diallyldimethylammonium chloride) needed to reach the same effect. This was found to be due to the lower molecular weight and lower charge density of hyperbranched polymers. The lower molecular mass allowed penetration of these polymers into pores of fibers that resulted in higher polymer consumption before removal of the dissolved and colloidal substances from the fiber suspensions. A lower charge density further resulted in a higher saturation adsorption of the hyperbranched polymer. Experiments with both DCS and model-latex particles showed that the initial increase in relative turbidity was due to the aggregation of particles before fixation to fibers. The results from quartz crystal microbalance with dissipation (QCM-D) experiments showed that the efficiency of hyperbranched polymer and poly-DADMAC was similar even if they had different structure. Therefore, this study highlights the importance of molecular mass and charge density of the polymers as well as the surface structure of polymer layers which in turn gives implications for development of new structures of fixing agents.
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