Poly(Ethylene Oxide) Star Polymer Adsorption at the Silica/Aqueous Interface and Displacement by Linear Poly(Ethylene Oxide)
2013 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 12, 3999-4007 p.Article in journal (Refereed) Published
Multiarm star copolymers with approximately 460 poly(ethylene oxide) (PEO) arms that have a degree of polymerization N = 45 were synthesized via atom transfer radical polymerization (ATRP) of PEO-methacrylate macro-monomers in the presence of divinyl benzene cross-linkers. These are an example of molecular or nanoparticulate brushes that are of interest as steric stabilizers or boundary lubrication agents when adsorbed from solution to a solid/aqueous interface. We use ellipsometry to measure adsorption isotherms at the silica/aqueous interface for PEO star polymers and linear PEO chains having molecular weights comparable either to the star polymer or to the individual arms. The compactness of the PEO star polymers (molecular weight 1.2 x 10(6)) yields a saturation surface excess concentration that is approximately 3.5 times greater than that of the high molecular weight (1 X 10(6)) linear PEO. Adsorption of low molecular weight (6000) linear PEO was below the detection limit. Competitive adsorption experiments were conducted with ellipsometry, complemented by independent quartz crystal microbalance with dissipation (QCM-D) measurements. Linear PEO (high molecular weight) displaced preadsorbed PEO star polymers over the course of approximately 1.5 h, to form a mixed adsorbed layer having not only a significantly lower overall polymer surface excess concentration, but also a significantly greater amount of hydrodynamically entrapped water. Challenging a preadsorbed linear PEO (high molecular weight) layer with PEO star polymers produced no measurable change in the overall polymer surface excess concentration, but changes in the QCM-D energy dissipation and resonance frequency suggested that the introduction of PEO star polymers caused a slight swelling of the layer with a correspondingly small increase in entrapped water content.
Place, publisher, year, edition, pages
2013. Vol. 29, no 12, 3999-4007 p.
Boundary lubrications, Competitive adsorption, Degree of polymerization, High molecular weight, Poly (ethylene oxide) (PEO), Quartz crystal microbalance with dissipation, Resonance frequencies, Surface excess concentration
Other Chemistry Topics
IdentifiersURN: urn:nbn:se:kth:diva-122348DOI: 10.1021/la305085aISI: 000316847200018ScopusID: 2-s2.0-84875576620OAI: oai:DiVA.org:kth-122348DiVA: diva2:622542
QC 201305222013-05-222013-05-202013-05-22Bibliographically approved