Molecular Orientation in Langmuir Monolayers Containing the [M(dmit)2]n-Anion Determined from Surface Pressure and Surface Potential Isotherms

Hughes, A.; Taylor, and D. M.; Underhill, Allan E.

doi:10.1021/la9807154

Cited by 5 publications

(1 citation statement)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Repeated compression−expansion circles showed reversible behavior up to 12 mN/m while noticeable hysteresis loops were recorded upon decompression started above the high-pressure transition (dotted line in Figure ). A similar behavior was previously observed for some PEO−lipid conjugates 26 as well as for other polymers ,,− and was also attributed to monolayer collapse. For PEOs and PEO−lipid conjugates, collapse pressures were previously reported in a range of 10−16 mN/m. ,, Interestingly, surface pressure at which the plateau corresponding to monolayer collapse occurs was found to vary with the length of hydrophobic anchors on PEO−lipid conjugates.…”

Section: Discussionsupporting

confidence: 86%

High-Pressure Transition of a Poly(ethylene glycol)-Grafted Phospholipid Monolayer at the Air/Water Interface

Tsukanova

Salesse

2003

Macromolecules

View full text Add to dashboard Cite

Monolayer behavior of a poly(ethylene glycol)-grafted distearoylphosphatidylethanolamine with PEG molecular weight 5000 (DSPE-PEG5000) was studied by a variety of experimental methods. Slope changes in the surface pressure-molecular area (π-A) isotherm suggest two transitions in the DSPE-PEG5000 monolayer upon compression which were previously attributed to conformational changes in the polymeric moiety. However, comparative analysis of our experimental data implies that the second slope change in the isotherm at π ≈ 18 mN/m originates from the monolayer collapse. As visualized by Brewster angle and atomic force (AFM) microscopy, the fluid homogeneous DSPE-PEG5000 monolayer is unable to sustain high pressures and collapses through vesicular structures formed as a result of 2D to 3D relaxation of an overcompressed film. AFM topographic images provided a height value of 9 nm for the collapsed structures on top of the monolayer, which can be referred to as the height of DSPE-PEG5000 lamellar structures. Thus, the collapse at a surprisingly low surface pressure implies that a distinct region where the PEG5000 moiety would adopt a brush conformation is probably never achieved for the DSPE-PEG5000 monolayer. Ellipsometric measurements of monolayer thickness confirm that although an elongated conformation is developed prior to the monolayer collapse, this conformation is better described as an "extended mushroom" rather than a "brush".

show abstract