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Adsorption of Low charge Density Polyelectrolyte Containing Poly(ethylene oxide) Side chains on Silica: Effects of Ionic strength and pH
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
Department of Polymer Chemistry, Vilnius University.
Department of Polymer Chemistry, Vilnius University.
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2005 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 38, no 14, 6152-6160 p.Article in journal (Refereed) Published
Abstract [en]

Adsorption characteristics of a random copolymer of poly(ethylene oxide) monomethyl ether methacrylate and methacryloxyethyl trimethylammonium chloride (PEOMENIA:METAC) on silica were studied using stagnation point adsorption reflectometry (SPAR), quartz crystal microbalance with dissipation (QCM-D), and contact angle techniques. The PEOMEMA:METAC copolymer used in this study is a low charge density polyelectrolyte, with 2% of the monomer units carrying permanent positive charges and 98% containing poly(ethylene oxide) side chains that are approximately 45 repeating units long. The surface excess was determined as a function of pH and concentration of indifferent electrolyte. It was found that the presence of a small amount of 1: 1 electrolyte decreases the adsorbed amount significantly. Further, increasing the pH at a constant ionic strength, 10 mM, results in decreasing surface excess. It is suggested that the adsorption is realized via a combination of non-Coulomb interactions between the poly(ethylene oxide), PEO, grafts and protonated silanol groups at the silica-solution interface and an electrostatic interaction between the charged segments and the oppositely charged surface. Increasing pH and/or salt concentration results in progressive charging of the silica surface with the consequent decrease in affinity between silica and PEO, explaining the decrease in the adsorbed amount of the polymer.

Place, publisher, year, edition, pages
2005. Vol. 38, no 14, 6152-6160 p.
Keyword [en]
Adsorption; Ammonium compounds; Contact angle; Copolymers; Electric charge; Ionic strength; pH effects; Polyethylene oxides; Quartz; Reflectometers; Silica; Charge density; Low charge density polyelectrolytes; Quartz crystal microbalance with dissipation (QCM-D); Stagnation point adsorption reflectometry (SPAR)
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-8143DOI: 10.1021/ma050851xISI: 000230376400041Scopus ID: 2-s2.0-22944446391OAI: oai:DiVA.org:kth-8143DiVA: diva2:13388
Note
QC 20100813Available from: 2008-03-27 Created: 2008-03-27 Last updated: 2010-08-13Bibliographically approved
In thesis
1. Poly(Ethylene Oxide) Based Bottle-Brush Polymers and their Interaction with the Anionic Surfactant Sodium Dodecyl Sulphate: Solution and Interfacial Properties
Open this publication in new window or tab >>Poly(Ethylene Oxide) Based Bottle-Brush Polymers and their Interaction with the Anionic Surfactant Sodium Dodecyl Sulphate: Solution and Interfacial Properties
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The aim of this thesis work is to study the physico-chemical properties of poly(ethylene oxide), PEO, based brush polymers both in solution and at solid/aqueous interfaces. The importance of studying the surface properties of brush polymers can be related to a broad spectrum of interfacial-related applications such as colloidal stability, lubrication, detergency, protein repellency to name a few. In many applications it is desirable to form brush-like structures through simple physisorption. In this context the surface properties of PEO based brush polymers differing in molecular architecture were studied, using ellipsometry and surface force apparatus (SFA), to gain some understanding regarding the effect of molecular architecture on the formation of brush structures. The molecular architecture was varied by varying the charge/PEO ratio along the backbone. This study demonstrates that the formation of a brush structure at solid/aqueous interface is due to interplay between the attraction of the backbone to the surface and the repulsions between the PEO side chains. An optimal balance between the two antagonistic factors is required if one aims to build a well-defined brush structure at the interface. In this study the brush-like structures are formed when 25-50% of the backbone segments carry poly(ethylene oxide) side chains. Scattering techniques such as light and neutron reveal that these brush polymers are stiff-rods up to a charge to PEO ratio of 75:25. These stiff PEO brush polymer easily replace the more flexible linear PEO at the silica/water interface, the reason being that the entropy loss on adsorption is smaller for the brush polymer due to its stiff nature.  Polymer-surfactant systems play a ubiquitous role in many technical formulations. It is well known that linear PEO, which adopts random coil conformation in aqueous solution, interact strongly with the anionic surfactant, Sodium Dodecyl Sulphate (SDS). It is of interest to study the interaction between SDS and brush PEO owing to the fact that the PEO side chains have limited flexibility as compared to the linear PEO.  The interaction between brush PEO and the anionic surfactant SDS in solution are studied using different techniques such as NMR, tensiometry, SANS and light scattering. The main finding of this study is that the interaction is weaker compared to the linear PEO-SDS interactions which poses an interesting question regarding the role of chain flexibility in polymer-surfactant interactions.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. x, 68 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:17
Keyword
PEO brush polymers, brush polymers, PEO, poly(ethylene oxide), polymer-surfactant, sodium dodecyl sulphate (SDS), Ellipsomtery, PEO-SDS interactions
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-4680 (URN)978-91-7178-900-6 (ISBN)
Public defence
2008-04-11, E2, KTH, Lindstedtsvägen 26, Stockholm, 09:00
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Supervisors
Note
QC 20100813Available from: 2008-03-27 Created: 2008-03-27 Last updated: 2010-08-13Bibliographically approved

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