title: Reduction of friction at oxide interfaces upon polymer adsorption from aqueous solutions.
abstract: Reduction of the interfacial friction for the contact of a silicon oxide surface with sodium borosilicate in aqueous solutions has been accomplished through the adsorption of poly(L-lysine)-graft-poly(ethylene glycol) on one or both surfaces. Spontaneous polymer adsorption has been achieved via the electrostatic attraction of the cationic polylysine polymer backbone and a net negative surface charge, present for a specific range of solution pH values. Interfacial friction has been measured in aqueous solution, in the absence of wear, and on a microscopic scale with atomic force microscopy. The successful investigation of the polymer-coated interfaces has been aided by the use of sodium borosilicate microspheres (5.1 microm diameter) as the contacting probe tip. Measurements of interfacial friction as a function of applied load reveal a significant reduction in friction upon the adsorption of the polymer, as well as sensitivity to the coated nature of the interface (single-sided versus two-sided) and the composition of the adsorbed polymer. These measurements demonstrate the fundamental opportunity for lubrication in aqueous environments through the selective adsorption of polymer coatings.
authors.affiliation: Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Yan
authors.forename: Scott S
authors.initials: SS
authors.lastname: Perry
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Spencer
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Pasche
authors.forename: Susan M
authors.initials: SM
authors.lastname: De Paul
authors.forename: Marcus
authors.initials: M
authors.lastname: Textor
authors.forename: Min Soo
authors.initials: MS
authors.lastname: Lim