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Desorption of bottle-brush polyelectrolytes from silica by addition of linear polyelectrolytes studied by QCM-D and reflectometry
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
2008 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 323, no 2, 223-228 p.Article in journal (Refereed) Published
Abstract [en]

The possibility of exchanging adsorbed layers of PEO(45)MEMA:METAC-X brush polyelectrolytes (with two different charge densities, 10 and 75 mol%, denoted by X), with poly(MAPTAC), a highly charged linear polyelectrolyte, was investigated by quartz crystal microbalance with dissipation and reflectometry. The studies were conducted on a silica substrate at pH 10, conditions under which only electrostatic interactions are effective in the adsorption process. Based on the results, it was concluded that PEO(45)MEMA:METAC-10 forms an inhomogeneous layer at the interface through which poly(MAPTAC) chains can easily diffuse to reach the surface. On the other hand, the PEO(45)MEMA:METAC-75 layer was not affected when exposed to a poly(MAPTAC) solution. We argue that the observed effect for PEO(45)MEMA: METAC-75 is due to the formation of a homogeneous protective brush layer, in combination with the small difference in surface affinity between the bottle-brush polyelectrolyte and poly(MAPTAC), together with the difficulty of displacing highly charged polyelectrolyte chains once they are adsorbed on the oppositely charged surface. We also use the combination of QCM-D and reflectometry data to calculate the Water content and layer thickness of the adsorbed layers. (c) 2008 Elsevier Inc. All rights reserved.

Place, publisher, year, edition, pages
2008. Vol. 323, no 2, 223-228 p.
Keyword [en]
polyelectrolyte, bottle-brush polyelectrolyte, brush polyelectrolyte, comb polyelectrolyte, linear polyelectrolyte, charge density, side chain density, poly(ethylene oxide), QCM-D, reflectometry, silica, adsorbed mass, sensed mass, dissipation, adsorption, desorption, QUARTZ-CRYSTAL MICROBALANCE, CHARGE-DENSITY, SIDE-CHAIN, CATIONIC POLYELECTROLYTES, COMPETITIVE ADSORPTION, PROTEIN ADSORPTION, POLYMERS, KINETICS, LAYERS, FILMS
Identifiers
URN: urn:nbn:se:kth:diva-14001DOI: 10.1016/j.jcis.2008.04.022ISI: 000256743300004Scopus ID: 2-s2.0-44649186817OAI: oai:DiVA.org:kth-14001DiVA: diva2:328965
Note
QC20100707Available from: 2010-07-07 Created: 2010-07-07 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Adsorption behaviour of bottle-brush and block copolymers at solid-liquid interfaces
Open this publication in new window or tab >>Adsorption behaviour of bottle-brush and block copolymers at solid-liquid interfaces
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis was spurred on by needs of current scientific and technological developments in the area of surface modification by use of adsorbed polymer layers. The importance of surface properties of polymer layers can be imparted in a broad spectrum of interfacial-related applications like lubrication, colloidal stability, detergency, and protein resistant surfaces, to just mention a few. Irrespective of all areas of application an underlying factor in all is the deep implication and footprint the molecular architecture has on the interfacial properties of polymer layers. In this context this thesis has the intention of raising awareness of the importance of the polymer architecture on interfacial behavior and the stability of layers formed by bottle-brush polymers and by temperature responsive block copolymers under different conditions. The first part of this thesis work was largely devoted to the surface properties of a series of cationic bottle-brush polymers, consisting of a main chain carrying charges and poly(ethylene oxide) (PEO) side chains close to randomly distributed along the backbone. Here particular attention was devoted to varying the molecular architecture by changing the charge/PEO ratio along the backbone. The studies demonstrated that the surface excess of the polymers went through a maximum as the number of backbone charges increased. Furthermore, the bottle-brush adlayers revealed sensitivity to changes in both ionic strength and pH when the numbers of backbone charges were relatively low. Layer properties were comprehensively elucidated by determining not only the adsorbed mass, but also layer thickness, water content and layer viscoelasticity. The change in these properties during formation of the adsorption layer was found to be complex, demonstrating significant conformational changes in the layer. The studies aimed at creating surface coatings with good resistance against species of high surface affinity, with a central interest in proteins, elucidated the optimal balance of the bottle-brush structure. The results revealed two scenarios, depending on both the type of protein and the areal density (grafting density) of the PEO side chains at the silica surface, where either protein adsorption was suppressed or enhanced by the presence of adlayers of the bottle-brush polymers. Low protein adsorption was achieved when the polymers have enough electrostatic attachment points to ensure a strong binding to the surface and at the same time a sufficient amount of PEO side chains that screen the protein-surface interactions. In the second part of the thesis a combination of QCM-D, AFM and reflectometry techniques was employed to probe the interfacial characteristics of temperature responsive cationic diblock copolymers, poly(N-ivisopropylacrylamide)m-block-poly(3-acrylamidopropyl)trimethyl ammonium chloride)n. The adsorption of these polymers to silica was of a high affinity, with no dramatic structural changes occurring during the layer build-up. The temperature dependent behavior of the adlayers demonstrated that the polymer interfacial conformation could be reversibly altered merely by cycling temperature above and below the lower critical solution temperature (LCST). This was found to have significant effects on both surface forces and boundary lubrication.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xiii, 77 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:22
Keyword
Adsorption, Lubrication, Layer viscoelasticity, Protein repellency, Polymer architecture, Silica, Bottle-brush polymers, Poly(ethylene oxide), PEO, Block copolymer, Poly(N-isopropylacrylamide), QCM-D, AFM, Reflectometry
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-13213 (URN)978-91-7415-611-4 (ISBN)
Public defence
2010-06-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100707Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2011-02-04Bibliographically approved
2. Polyelectrolytes: Bottle-Brush Architectures and Association with Surfactants
Open this publication in new window or tab >>Polyelectrolytes: Bottle-Brush Architectures and Association with Surfactants
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis has the dual purpose of raising awareness of the importance of the mixing protocol on the end products of polyelectrolyte-oppositely charged surfactant systems, and to contribute to a better understanding of the properties of bottle-brush polyelectrolytes when adsorbed onto interfaces.

In the first part of this thesis work, the effects of the mixing protocol and the mixing procedure on formed polyelectrolyte-oppositely charged surfactant aggregates were investigated. It was shown that the initial properties of the aggregates were highly dependent on the mixing parameters, and that the difference between the resulting aggregates persisted for long periods of time.

The second part of the studies was devoted to the surface properties of a series of bottle-brush polyelectrolytes made of charged segments and segments bearing poly(ethylene oxide) side chains; particular attention was paid to the effect of side chain to charge density ratio of the polyelectrolytes. It was shown that the adsorbed mass of the polyelectrolytes, and the corresponding number of poly(ethylene oxide) bearing segments at the interface, went through a maximum as the charge density of the polyelectrolyte was increased. Also, it was found that bottle-brush polyelectrolyte layers were desorbed quite easily when subjected to salt solutions. This observation was rationalized by the unfavourable excluded volume interactions between the side chains and the entropic penalty of confining them at an interface, which weaken the strength of the binding of the polyelectrolytes to the interface. However, it was shown that the same side chains effectively protect the adsorbed layer against desorption when the layer is exposed to solutions containing an oppositely charged surfactant. Investigation of the lubrication properties of the bottle-brush polyelectrolytes in an asymmetric (mica-silica) system also related the observed favourable frictional properties to the protective nature of the side chains. The decisive factor for achieving very low coefficients of friction was found to be the concentration of the side chains in the gap between the surfaces. Interestingly, it was shown that a brush-like conformation of the bottle-brush polyelectrolyte at the interface has little effect on achieving favourable lubrication properties. However, a brush-like conformation is vital for the resilience of the adsorbed layer against the competitive adsorption of species with a higher surface affinity.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 39 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:18
Keyword
Polyelectrolyte, Surfactant, Bottle-Brush Polyelectrolyte, Comb Polyelectrolyte, Non-Equilibrium State, Polymer Architecture, Adsorption, Desorption, Association, Excluded Volume, Light Scattering, SFA, AFM, QCM-D, Turbidimeter, Mica, Silica, Surface Forces
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-4683 (URN)978-91-7178-903-7 (ISBN)
Public defence
2008-04-18, F3, Lindstedsvägen 28 100 44, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100830Available from: 2008-03-27 Created: 2008-03-27 Last updated: 2012-01-20Bibliographically approved

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