| 1. |
- Varga, Imre, et al.
(författare)
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Effect of graft density on the nonionic bottle brush polymer/surfactant interaction
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:19, s. 11383–11389-
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Tidskriftsartikel (refereegranskat)abstract
- The effect of graft density on the interaction of nonionic bottle brush polymers with an anionic surfactant (sodium dodecyl sulfate) was investigated. The graft density of 45 units long poly(ethylene oxide) (PEO) side chains was varied in a wide range (30, 50, 75, 90, and 100%) on a methacrylate type polymer backbone. The surfactant binding isotherms were determined by the potentiometric method in the presence of 0.1 M sodium bromide. It was found that due to the grafting of the PEO chains to a polymer backbone the surfactant binding becomes significantly suppressed. The amount of bound surfactant at the critical micelle concentration (cmc) decreases almost 2 orders of magnitude compared to the binding on a linear PEO having a similar molecular weight. The binding of the surfactant was found to occur in cooperative fashion, though the critical aggregation concentration (cac) of the binding was found surprisingly small. This result was interpreted in terms of the surfactant aggregation numbers that were found much smaller in the case of the bottle brush polymers than in the case of linear PEOs due to the steric crowding of the grafted PEO chains. To confirm the results of the binding isotherm measurements, steady-state fluorescence probe (pyrene) measurements as well as static and dynamic light scattering measurements were performed.
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| 2. |
- Bastardo Zambrano, Luis Alejandro, et al.
(författare)
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Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR
- 2007
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 312, s. 21-33
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Tidskriftsartikel (refereegranskat)abstract
- 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 PEO45 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 Å. 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 PEO45 MEMA: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.
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| 3. |
- Claesson, Per M., et al.
(författare)
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Interfacial properties of bottle-brush polyelectrolytes
- 2007
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Ingår i: PROCEEDINGS OF BALTIC POLYMER SYMPOSIUM 2007. - Vilnius : VILNIUS UNIV.. - 9789955331506 ; , s. 77-81
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Konferensbidrag (refereegranskat)abstract
- This article is focused on interfacial properties of bottle brush polyelectrolytes, where side-chains are attached along a polymer backbone. This class of polymer has been much less studied than block copolymers, which is particularly true for bottle brush polyelectrolytes with a high graft density. We have explored how the graft density and charge density of such polymers affect surface properties, as well as some bulk properties. The adsorption of this class of polymer onto negatively charged silica and mica surfaces has been determined. On mica adsorption is driven by electrostatic forces whereas on silica both electrostatic forces and interactions between silica and ethylene oxide chains drive the adsorption. On silica the adsorbed amount is very sensitive to solution ionic strength and pH. We also report on surface interactions and frictional forces obtained between surfaces coated with bottle brush polyelectrolytes.
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| 4. |
- Dédinaité, Andra, et al.
(författare)
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Interfacial properties of chitosan-PEO graft oligomers: Surface competition with unmodified chitosan oligomers
- 2006
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Ingår i: Progress in Colloid and Polymer Science. - Berlin/Heidelberg : Springer-Verlag. - 0340-255X .- 1437-8027. ; 132, s. 124-130
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Tidskriftsartikel (refereegranskat)abstract
- Oligomers of chitosan carrying 45 units long poly(ethylene oxide), PEO, chains grafted to the C-6 position of the sugar units were prepared using a novel synthesis route. The graft density was high, close to one poly(ethylene oxide) chain grafted to each sugar unit of the chitosan oligomer but a small fraction of unreacted chitosan remained in the sample. The molecular weight distribution of the sample was determined using GPC. The interfacial properties of the chitosan-PEO graft oligomers were evaluated using X-ray photoelectron spectroscopy and surface force measurements. It was found that the small fraction of unreacted chitosan was significantly enriched at the solid-solution interface on negatively charged muscovite mica surfaces. The interactions between chitosan-PEO oligomer coated surfaces were found to be dominated by the extended PEO chains, and at high coverage the measured forces were consistent with those expected for polymer brushes. Addition of salt up to 10 mM did not result in any significant desorption of preadsorbed oligomer layers.
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| 5. |
- Dedinaite, Andra, et al.
(författare)
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Solution properties of bottle-brush polyelectrolytes
- 2007
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Ingår i: PROCEEDINGS OF BALTIC POLYMER SYMPOSIUM 2007. - 9789955331506 ; , s. 112-116
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Konferensbidrag (refereegranskat)abstract
- Aqueous solution properties of bottle brush polyelectrolytes, where side-chains are attached to a polymer backbone, have been studied. The side chains consist of 45 units long poly(ethylene oxide) groups and the backbone is of the methacrylate type. Small-angle X-ray scattering (SAXS) was used to elucidate the solution conformation of this class of polymer and how it is affected by the side chain density and charge density. The effect of temperature on the solution conformation, and in particular the side chain extension, has also been quantified. At higher concentrations the interactions between the polymer chains in solution affects the scattering, and it is shown that this interaction is well described by a model originally developed for wormlike micelles.
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| 6. |
- Gorochovceva, N., et al.
(författare)
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Chitosan-N-poly(ethylene glycol) brush copolymers : Synthesis and adsorption on silica surface
- 2005
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 41:11, s. 2653-2662
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan-N-poly(ethylene glycol) brush copolymers with different degree of substitution (DS) were synthesized via reductive amination of chitosan by rnethoxy poly(ethylene glycol) (MPEG) aldehyde. Chitosan-N-MPEG copolymers were high-molecular-weight products with desirable DS; solubility and solution viscosity of those copolymers depended on the method of the synthesis of MPEG aldehyde and on DS. Synthesis of MPEG aldehyde by the use of TEMPO radical/BAIB was not suitable because of partial oxidation of methoxy groups of MPEG resulting in bifunctional PEG derivatives leading to cross-linking. Adsorption studies of chitosan-N-MPEG graft copolymers oil silica surface show that these polymers adsorb in highly hydrated layers.
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| 7. |
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| 8. |
- Shovsky, Alexander V., et al.
(författare)
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Formation and stability of soluble stochiometric polyelectrolyte complexes: Effects of charge density and polyelectrolyte concentration
- 2009
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Ingår i: Journal of Dispersion Science and Technology. - : Informa UK Limited. - 0193-2691 .- 1532-2351. ; 30:6, s. 980-988
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Tidskriftsartikel (refereegranskat)abstract
- Sterically stabilized polyelectrolyte complexes with stoichiometric composition between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights have been prepared. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion and a range of brush copolymers with various molar ratio (X = 1, 0.75, 0.5, 0.25) of the poly-methacryloxyethyl trimethylammonium chloride poly(METAC) and the nonionic poly (ethylene oxide) methyl ether methacrylate poly(PEO45MEMA) were used as polycations. Formation and stability of PECs have been investigated by dynamic and static light scattering (LS), turbidity and electrophoretic mobility measurements as a function of polyelectrolyte solution concentration and charge density of the cationic polyelectrolyte. The data obtained suggest that the PEO45- rich systems, NaPSS/PEO45MEMA:METAC-25 and NaPSS/PEO45MEMA: METAC-50, form small, water-soluble, molecular complexes having nonspherical shape. The PEO45-poor NaPSS/PEG45MEMA:METAC-75 form turbid colloidal dispersions, whereas insoluble PECs were revealed for the PEO45-free NaPSS/METAC system. The aggregation level of the PEO45-poor systems is mainly controlled by the concentration of the component solutions used for the preparation of PECs, whereas the aggregation of PEO45-rich nanoparticles is prevented by means of steric stabilization. Electrophoretic mobility data indicate a close to charge neutral state of the generated polyelectrolyte complexes.
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