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Interaction between hydrophilic surfaces in triblock copolymer solution
YKI – Ytkemiska institutet.
YKI – Ytkemiska institutet.
1998 (engelsk)Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, s. 7287-7291Artikkel i tidsskrift (Fagfellevurdert)
Abstract [en]

We report on the interactions between fused quarts surfaces immersed in solutions of low molecular weight nonionic homopolymers and triblock copolymers. The polymers studied were a polyethylene oxide homopolymer and a triblock copolymer of the type polyethylene oxide - polytetrahydrofuran - polyethylene oxide. The surface force measurements were done by the interfacial gauge technique. In water, a strong repulsive force was observed at short surface separations. Similar effects, previously attributed to the presence of hydration water, are due to electro-steric interactions imposed by partial stabilisation and formation of a gel layer on silica. Interestingly, this repulsive interaction was suppressed and not noticed when small amounts of polymers were adsorbed, or when water was substituted for ethanol as medium. Adsorbed polymers induce a long range steric repulsion of a quite different character. However, in solutions of PEO homo polymers, when the distance between the surfaces decreases, the repulsive interaction levels off. It remains more or less constant with decreasing surface-to-surface distance in this region. In this depletion range polymers are partly expelled from the gap between the surfaces. When the surfaces were separated after compression, an adhesive force was observed. This indicates that some adsorbed macromolecules remained in the gap after compression. For the PEO homopolymer the interaction both on approach and separation, showed a weak dependence on polymer concentration over a wide range. For the block copolymers, however, a stronger concentration dependence was observed. For instance, close to the surface aggregation concentration we observed an attractive interaction at some distances. This attraction is caused by bridging of surface micelles. It does not shows up at higher copolymer concentrations where the surface are fully covered by polymers. At low copolymer concentrations the copolymer aggregates are expelled to some extent from the gap between the surfaces at small surface-to surface distances. This depletion leads to a weak distance indifferent region with a small constant repulsion. At higher concentrations the interaction is purely repulsive at all surface-to surface distances, at both approach and separation. We studied also the role of solvent on interaction between surfaces in copolymer solutions. Adsorption of copolymers to silica from ethanol did not show long range interaction patterns but was sufficient to induce adhesion between the surfaces.

sted, utgiver, år, opplag, sider
1998. Vol. 14, s. 7287-7291
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Identifikatorer
URN: urn:nbn:se:ri:diva-27256OAI: oai:DiVA.org:ri-27256DiVA, id: diva2:1054260
Merknad
A1240Tilgjengelig fra: 2016-12-08 Laget: 2016-12-08 Sist oppdatert: 2017-11-29bibliografisk kontrollert

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