| Abstract
| - The interactions between two mica surfaces bearing a fourth-generation carbosilane dendrimer (modifiedto expose −OH groups on its outer surface) were studied across a toluene medium, using a surface forcebalance capable of measuring shear as well as normal forces. Normal force measurements indicate thatthe dendrimers adsorb from dilute toluene solution (ca. 5 × 10-4 w/w) as a monolayer on each surface. Twosuch interacting surfaces experience a longer-ranged van der Waals attraction followed by strong short-range adhesion (probably of dipolar origin) as the adsorbed dendrimers come into contact. Within the rangeof our parameters, the dendrimer layers were incompressible normal to the surfaces. Friction versus loadprofiles were measured at different shear velocities, revealing marked stick-slip sliding, whereas themagnitude of the yield stress increased with longer times of contact and with normal pressure. Thissuggests that over time scales comparable with the experimental times the interacting layers rearrangeto optimize their interfacial shear strength. The behavior of these −OH-exposing carbosilane dendrimersdiffers qualitatively from that of CH3-exposing poly(propyleneimine) dendrimers studied earlier, a differenceattributable to the much more polar nature of the hydroxyl groups.
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