How polymer surface diffusion depends on surface coverage
Zhao, Jiang; Granick, Steve
Source PublicationMACROMOLECULES
AbstractMeasurements are presented of how surface diffusion of flexible polymers at the solid-liquid interface is controlled by surface coverage. Surface coverage is varied over the full range from dilute to saturated surface coverage. The method of measurement is fluorescence correlation spectroscopy (FCS), and the systems are poly(ethylene oxide) (PEG) and dextran adsorbed onto methyl-terminated self-assembled monolayers in buffered aqueous solution. A detailed study of PEG (M(w) = 10 800 g mol(-1)) shows nonmonotonic behavior. The translational diffusion coefficient (D) at first increases with increasing surface concentration, presumably because the number of adsorption sites per molecule decreases as chains switch from pancake to loop-train-tail conformation. Excellent fits to behavior characteristic of a single diffusion process argue against aggregation or crystallization in the adsorbed state. In-situ ellipsometry measurements appear to rule out conformation changes to a hypothetical helical structure, as this would introduce birefringence to the adsorbed polymer layer causing deviations from the observed linear growth of apparent layer thickness with increasing surface coverage. For all three samples studied (PEG of M(w) = 10 800 and 20 000 g mol(-1) and also dextran with M(w) = 10 000 g mol(-1)), D at surface coverages larger than the estimated surface overlap concentration slow by 1 order of magnitude, presumably reflecting crowding and entanglement with neighboring chains.
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WOS IDWOS:000244160800064
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Cited Times:54[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorGranick, Steve
Affiliation1.Univ Illinois, Dept Mat Sci & Engn, Urbana, IL 61801 USA
2.Univ Illinois, Dept Chem, Urbana, IL 61801 USA
3.Univ Illinois, Dept Phys, Urbana, IL 61801 USA
4.Chinese Acad Sci, Inst Chem, Joint Lab Polymer Sci & Mat, State Key Lab Polymer Phys & Chem, Beijing 100080, Peoples R China
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GB/T 7714
Zhao, Jiang,Granick, Steve. How polymer surface diffusion depends on surface coverage[J]. MACROMOLECULES,2007,40(4):1243-1247.
APA Zhao, Jiang,&Granick, Steve.(2007).How polymer surface diffusion depends on surface coverage.MACROMOLECULES,40(4),1243-1247.
MLA Zhao, Jiang,et al."How polymer surface diffusion depends on surface coverage".MACROMOLECULES 40.4(2007):1243-1247.
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